Improvements in Thermodynamic Processes for Converting, by the Agency of Vapour Pressure, Heat into Work, and in Apparatus for Effecting the same.
Year: 1895

page_text: Date of Application, 19th Nov., 1895-Accepted, 14th Mar., 1896
DI BUITICATION.
[Communicated from abroad by Mrs. AGNES BATES WELLINGTON, Gentlewoman,
of No. 125 East 21st Street, in the City of New York, United States of
America.]
Improvements in Thermodynamic Processes for Converting, by the
Agency of Vapour Pressure, Heat into Work, and in Apparatus
for Effecting the same.
I PHILIP ARTHUR NEWTON of The Office for Patents, 6 Bream's Buildings,
Chancery Lane in the County of London, Patent Agent, do hereby declare the
nature of this invention and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement (as
communicated to me from abroad) :-
:-
The present invention provides a new thermodynamic process for converting heat
into work by the agency of vapor pressure whereby the percentage of the heat
supply convertible into work is increased very largely above that practically
attainable by processes now in use, or to from fifty to eighty per cent. of the total
heat supply, while at the same time a large reduction in the weight, bulk and cost
of engines is effected, and the existing danger of explosion and of injury from
temperature strains largely eliminated. The percentage of saving in bulk and
weight is necessarily incapable of exact expression, but the boilers, in which the
largest reduction is effected, may be reduced to less than one-tenth of their present
bulk and weight per unit of work, while the engines proper are somewhat reduced
below the simplest and most wasteful types now in use and, in comparison with the
present more economical types, the bulk and weight of the engine proper may be
only one third to one-fifth as great.
"
This new process and resulting engine differ so radically from any known forms of
air or vapor heat engines that their nature cannot be indicated even approximately
by applying or extending to them any designations now known to science, but they
are herein designated for convenience, as the "Series process and engine. The
series engine introduces no important novelties of mechanical detail except in the
construction of its boilers and condensers and the way of supplying heat thereto, but
the radical nature of the deviations of its process from current practice may be
indicated in a measure by noting that its economy does not depend upon or vary
with either the quantity of vapour used or the degree of expansion, but is often in
inverse ratio thereto, and that the quantity of vapor used is in fact relatively
large, and the ratio of expansion used small, rarely exceeding two to three.
The basic element of this new process, by which alone it is rendered practicable,
lies in a new general process for the generation of vapor pressure, which is broadly
applicable, not only to the series process, but to all new or old processes requiring
the generation of steam or other vapor for any purpose whatsoever, whether for
running heat engines or for doing any heating or other work for which vapor
pressure may be required. In all such cases, with possible minor exceptions of no
significance, this new general process of pressure generation may be used with
marked advantage, effecting among other things important ends, as follows:
A reduction in the bulk and weight of boilers per unit of power is effected which,
even when moderately stated, appears quite incredible. When applied to steam
generation for the now usual or Watt process, it extends so far that the boiler is

page_text: practically eliminated as a factor in the weight and bulk of engines, and may be
more accurately conceived of as a mere enlargement of the feed-pipe, in which the
water supply flashes into steam as it moves along. Steam has actually been
produced at the rate of one hundred horse power per cubic foot (28.316 cubic
decimeters) of total boiler bulk, and still more than this can be produced, though
ordinarily about one-half that quantity is more expedient, but even the latter gives
two hundred to three hundred times the usual boiler capacity per unit of volume.
There is, at the same time, a practically complete elimination of injurious
temperature strains, less than one per cent. of the usual quantity of working
substance is required, heat may be applied or removed as quickly as desired, and
steam may be raised from cold water almost instantaneously. There is also a
practically complete absence of any tendency to foam or make wet steam, and of
risk of explosion.
It necessarily follows from these facts that the new general process of generating
vapor pressure can be used with decided advantage whenever it is desired to produce
steam in considerable quantities for any purpose. Nevertheless its chief economic
advantage is that it renders possible complete new processes for the generation of
power from heat, one of which, the most perfect which I have been able to devise,
is the series process aforesaid. I proceed to describe in order, first: the general
process of steam generation above referred to and its application to existing
processes, second: the series engine process aforesaid, which is technically only a
particular caɛe under this general process, and third: apparatus for carrying out
these processes and a new boiler especially designed for use therewith.
The new general process of pressure generation depends upon the principle of the
dissociation of the fire or other irregular source of heat from the boiler or other
pressure generator containing the confined working substance, in order that the
effective connection between the two may be secured by a heat conveying substance
which is passed from the source of heat to the pressure generator, and which, in the
typical case and except for special reasons, is returned to the source of heat to be
reheated, so as to move in a closed cycle; being alternately heated to a desired or
convenient point, passed to the pressure generator containing the working substance,
cooled to a desired or convenient point by the surrender of heat to the working
substance, and returned directly or indirectly to the source of heat to be reheated.
In special cases the heat carrying substance is not returned to be reheated, but
worked in open cycle, a new mass being continually received, heated, cooled and
discharged.
The heat conveying substance I call for convenience the circulating fluid, whether
it be worked in closed or open cycle. It is preferably a liquid, but may be solid or
gaseous in part or whole, as hereafter explained, and its sole function as a part of
this process is to flow around in passageways which are usually endless, being
preferably in continuous motion and under more or less careful regulation as to
speed and temperature, and thus to convey heat to the working substance. Having
such a hot fluid in motion, however, it may at times be convenient to take some
heat from it for some other use, and certain gains to this process may at times
result from doing so. The circulating fluid may consist either of one or of several
different heat conveying substances, circulated either as a common mass or, as is
often expedient for practical reasons, in two or more distinct sets of passageways,
but in either case it is spoken of collectively as the circulating fluid.
Among the cases in which it is inexpedient to use over and over a single mass of
circulating fluid these two are prominent: First, in certain applications of my
process, a surrounding mass of air or water already heated or partially heated to
the desired point by nature or in the practice of some other art may be drawn upon
for the circulating fluid, and there is then an obvious practical advantage in receiving
a fresh mass of circulating fluid from this existing supply instead of using a single
mass over and over in closed cycle. Second, in all cases when fire is used for heat,
a continuous supply of fresh air must be taken into the heater to support combustion,
and the gas thus used may most advantageously be made a part of the circulating

page_text: Aluid by first causing it to absorb as much as possible of otherwise rejected waste
heat on its way to the heater, and then, after it has supported combustion,
arranging to insure its reduction to an admissible temperature, and passing it
through the pressure generator as a part of the circulating fluid in order that it
may surrender further heat before discharge. With care to insure that this gas
shall be cooled down to a reasonably uniform and moderate temperature before
Buch use, it not only may be, but in large plants should be used as part of the
circulating fluid, and if so used it must be used in open cycle, even though the rest
of the circulating fluid is used in closed cycle. It will be understood, therefore,
that the term "circulating fluid" is intended to cover not only a fluid, a single mass
of which is used repeatedly, but also a fluid which is drawn from a supply,
utilized in transporting heat to the working substance, and then voided from the
mechanism.
As between air and water as a circulating fluid, each has decided theoretical
advantages. Air has the very great advantage of not being changed in physical
properties by any extremes of temperature, and also of being a supporter of
combustion, so that when air is used as the circulating fluid, the heater may be a
closed chamber in which fuel is burned in the circulating fluid itself at a regular
rate, such as just to supply the heat needed to raise it to the required temperature,
with a resulting large economy of fuel, which in the best applications of the process
may even rise to perfect economy of combustion, the gases being discharged no
hotter than when received. Being 815 times lighter than water the same propelling
pressure will drive it about ✓815 = 28.55 times as fast, and the friction loss will be
still less in proportion, thus in a measure compensating for its lack of mass and low
specific heat. For the opposite extremes of small engines for which simplicity is
an object and high economy relatively unimportant and large engines working
through a very great thermal range in order to realize high economy, air alone may
be a very suitable circulating medium. Air has the further great advantage in
certain special applications of the process that it may be caused to change in
temperature without any direct application of heat or cold, simply by changing its
status as compressed or uncompressed.
On the other hand, as a heat transmitter, air is extremely inefficient. A given
heating surface is from 30 to 100 times as efficient between water and water or
steam as between air and water or steam. Therefore a correspondingly great
excess of heating surface, or else of "thermal head," or difference between the
temperatures of the heating and the heated substances. is required if air be used
over what is required with water as a circulating fluid. Water has the great
advantage of a higher specific heat than any other known body and my experiments
indicate that it has also notably greater powers of imparting heat to metallic
surfaces than any other conveniently available fluid, but it has the great
disadvantage of being liquid at atmospheric pressures only between 0° and 100° C.
To overcome this deficiency by increasing the thermal range within which water is
liquid, it may be circulated under pressure, and this will often be expedient,
though it involves certain inconveniences even when the water is used in a closed
cycle, and still more in open cycle. As a leading motive for using water rather
than some other liquid will often be to use it in open cycle, water is not an entirely
desirable circulating fluid, and may rarely be useful for this end at all except when
its boiling point is artificially raised by circulating it under pressure. In special
applications of the process, water in the form of steam may serve as circulating
fluid, especially when it is only a small portion of the total mass, but such use is
not typical nor ordinarily expedient.
If steam were to constitute a considerable fraction of the circulating fluid the
question of how that steam should be generated would then arise, and if it be
generated in the ordinary way all the defects of practice which it is the purpose
of this invention to correct would still be retained. The use of steam or any other
vapor condensed from gaseous to liquid state in circulation, as the sole or main
constituent of the circulating fluid, is never expedient, and is not included within

page_text: the term "circulating fluid." Such a vapor condensed in circulation may, however,
be used as a small part of the total mass of a circulating fluid, of which the gases
of combustion form a part, for the incidental purpose of producing an induced
draught and to cool down the gases of combustion to a temperature approximating
more closely to that of the liquid circulation.
There are, however, a variety of other liquids, of which paraffine oil is an
example, which remain liquid within all extremes of temperature from 0° to 300° C.
or even more; which are chemically neutral and stable, even if subjected to long
continued alternations of these temperatures; which do not gum, and which may
be circulated with even less friction than water. They have in general a specific
heat of about 0.4, which means that they must be circulated about 24 times as fast
to supply the same quantity of heat per hour to the same surfaces; and I have
found them to have considerably less heat transmitting efficiency than water when
in contact with heating surfaces. But the lower specific heat is an advantage as it
enables the fluid to be circulated faster than it otherwise could; the speed at best
is slow; and on the whole these oils have most of the advantages of water with
some peculiarly their own, and they constitute a convenient and suitable circulating
medium when a liquid is used in a closed cycle, though requiring much more heating
surface for equal efficiency. When so used in closed cycle the scarcity or cost of
the liquid does not matter, nor even its noxiousness in a free state; since no great
quantity is used and there is little or no waste. There is therefore a wide range
of choice in regard to the components of the circulating fluid, but so far as I yet
know, either water or air or purified paraffine oil combine the most advantages
except as follows:-
As above stated, the circulating fluid may be solid in part or whole, that is, as a
pulverized substance, mixed or not with liquid or gas. An exclusively solid
circulation, in the form of a movable solid mass is a mere possibility, but it is
rather the rule than the exception that a combination of solid liquid and gaseous
elements gives a better circulating fluid than either one or two such elements alone.
Whether the base of the circulating fluid be liquid (except possibly in the case of
water) or gaseous, there is generally a decided advantage in mixing with it
mechanically some pulverized carbonaceous or other substance of good radiating
properties, while for certain extremes of both heat and cold which some of the best
applications of this process require, no liquid known to me has the requisite
physical properties, and only gases can be used.
The "working substance to which heat is supplied by surrender from the
circulating fluid may be any gaseous or liquid substance to which heat may be
applied while it is confined within a chamber with the effect of generating or
increasing therein a vapor pressure which enables the confined substance to do
useful work. In this Specification and the claims all gases are considered as the
vapors of liquids, whether ordinarily condensable or not. When used in connection
with an engine for producing motion, the term "working substance" refers only to
the substance which by its expansive pressure causes the motion, but when used
more broadly and without special reference to the mechanism in which the working
substance is used, the "work" to which the term is intended to refer includes any
sort of useful work which may be done by vapor pressure generated or increased
by heat, whether it be working a mechanical engine or securing any other result by
the surrender of part or of all of its heat or pressure.
"
The "dissociation
of the source of heat and working substance is simply a
thermal dissociation which may or may not be mechanical also. Ordinarily, two
parts which are intended to be thermally dissociated should not be mechanically
contiguous, but mechanical convenience may often render this expedient, even at
some slight sacrifice of thermal dissociation. Whenever the source of heat and
the working substance are so disposed that the circulating fluid may serve as the
effective thermal connection between them, to the exclusion of interference by
unregulated heat with the moderate and controllable action of the circulating fluid
as far as is practical, the source of heat and working substance are thermally

page_text: "dissociated" within the meaning of the term as used herein, although there may
be some considerable residue of direct action of the one upon the other by
conduction of heat through common metallic parts or otherwise.
By the development of the principle above outlined, in accordance with the
present invention, we attain or may attain a number of highly important ends.
We eliminate all temperature strains from the pressure generator, by subjecting it
only to a regulated and uniform heat. We may multiply many times the efficiency
of the heating surfaces when the circulating fluid is a liquid by securing liquid
instead of gaseous contact with the heating surfaces. More important than all
else, perhaps, we may radically modify for the better the functional action of the
pressure generator by applying our greatest heat at the top of the pressure
generator instead of the bottom and carrying the heating and the heated substance
in opposing currents past each other, the heating substance descending as it cools
while the heated substance rises as it grows hotter, thus producing differential
temperatures within the boiler, all its materials and contents being at all times
hottest at the top, coldest at the bottom, by necessary effect of the functional
action, whereas in every boiler to which fire is applied directly there exists a
reverse and injurious tendency and status. With a circulating fluid also we may
permeate the entire interior of the pressure generator with our heat supply, the
steam space as well as the water space.
The effect of these changes in practice and in the status of the pressure generator
is too important and far reaching to be explained in few words or to be at once
comprehended. When followed out to its legitimate results it is found to be
revolutionary, both as to the theory and the practice of both steam making and
steam using. The effect upon steam boiler practice is such that, as already stated,
the boiler practically vanishes as a factor in the bulk and cost of steam engine³,
and may more accurately be conceived of as a mere enlargement of the steam pipe
in which a liquid changes into gas as it moves along. The effect upon the theory
of steam generation is to establish broadly as a general theorem that the irregular
application of heat in bulk, and especially the unregulated heat of fire, to vaporizing
working substance under pressure is an error of process which is destructive of
economy. The effect upon the use of steam is to make possible complete new
processes for the conversion of heat into work with a percentage of economy
heretofore unattainable, as shown more fully later in connection with the complete
engine process.
While my improved process of pressure generation is of general application to
all known types of air or vapor heat engines, and to most other mechanisms in
which heat is caused to do useful work by the generation and application of vapor
pressure, it is best used, perhaps, in connection with various forms of steam
engines. The process will, therefore, be described with special application to
steam generation, reference being had to Figures 1 to 8 of the accompanying
drawings forming a part of this Specification in which are illustrated diagram-
matically the general features and some of the methods of application of this
general process.
Stated broadly as a general principle applicable generally to existing processes
utilizing vapor pressure, the nature of the alleged error of process above referred
to and the correction of which forms the basis of the invention may be explained
thus:
Fluctuations of 1,000° C.
Fire in large mass is an uncontrollable thing.
(1800° F.) or more may occur locally in a furnace within a few minutes or seconds
of each other and even greater fluctuations occur in the furnace as a whole at
longer yet frequent intervals. This exposes all the containing surfaces to intense
and irregular alternations of extreme heat and cold. Hence the first necessity for
reasonable lightness and durability is that these surfaces should be free to
expand and contract ad libitum without doing harm. To use the other side of the
same surfaces as the containing surfaces for a mass of an explosive substance under
pressure, but which yet by its conditions has a constant temperature, is illogical

page_text: .
and absurd. It is yoking together two discordant and antagonistic things, which
may possibly be done with safety, but only with costly precautions and occasional
failures. These two uses of the same chamber are antagonistic and naturally
require dissociation. The fire chamber needs only the passive resistance of fire-
.brick but no great strength; the steam and water chamber, if the heating as well
as the heated fluid may be at sensibly constant and controlled temperatures,
needs only static strength and no massiveness at all, but on the contrary, its
function demands all possible thinness and delicacy of surfaces that static strength
permits.
This first false step once taken, of making one what should be two, there is no
resource remaining but to take several other false steps to avoid the consequences
of the first. To resist the temperature strains alone we are compelled to make the
surfaces objectionably thick for heat transmitting purposes. The direct action of
fire upon them soon gives them also a non-conducting scale or coating, which alone
decreases by one-half to four-fifths their heat-transmitting capacity. Worse than
all, the fierce heat impacts make it absolutely necessary that all surfaces to which
they are applied shall be well immersed in water, which in turn requires that the
most intense heat shall be applied at or near the bottom of the boiler and of the
contained mass of liquid, and shall decrease in intensity toward the top, whereas
the best evaporative conditions require that it shall increase toward the top.
This error in the point of applying the most intense heat in its turn ensures that
nearly all the steam shall be generated at the bottom of the liquid instead of at the
top, and hence that it must rise through the entire mass of liquid to escape from it.
Thus arises a necessity for a violent circulation, in order that fresh liquid may be
continually flowing in from the side to replace that which is continually removed
. and carried upward from the most heated surfaces, not so much by evaporation as
by the mechanical action of the rising steam. This in turn makes it absolutely
necessary that there shall be within a large mass of rapidly circulating working
substance to serve as an equalizer and harmless receiver of these heat impacts and
to furnish a sufficient mass, not only to give a considerable depth of water over the
heated surfaces but also to fill certain otherwise inert side spaces for the downward
circulation to which from the nature of their function heat must not be applied
and which, therefore, only serve to increase the bulk of the boiler and working
substance without adding to the evaporation. It is true that the large mass of
contained working substance thus enforced has the slight additional use of giving
a small store of reserve power which may be drawn on for a few moments, but that
function also is better subserved otherwise. This large quantity of functionally
useless and inactive working substance makes the boiler a magazine of explosive
energy and so necessitates still greater strength, not for ordinary needs, but for
rare emergencies which exist only because of the uncontrolled and intense heat
impacts. Under my process when best applied there is needed only a small per cent.
of the usual mass of working substance.
This need for rapid circulation of a great mass of liquid in its turn requires that
the active heating surfaces shall be widely spaced, with large free intervals between
them for circulation; and this in its turn, with the requirement that all parts shall
be of massive strength, forbids the production of any large amount of heating
surface in a small space; and hence requires that what heating surface there is
shall be intensely active, and the ebullition from it intense and violent. This in
its turn demands that the external thermal head shall be large, and hence that
much heat shall be discharged to waste, and also ensures internally such violent
upward foaming from the most heated spots that a large amount of priming must
result; and this last, in its turn, requires a large and otherwise useless steam space
above the seething water, in order that in its comparative quiet some of this water
may drop back again out of the steam. Naturally, much of it refuses to drop
back, but remains in the steam.
Again, the intense and irregular heats used forbid our exposing this steam to
further heating surface to evaporate its entrained water and superheat the steam.

page_text: The gases must be discharged to waste still highly heated for the very reason that
they are so highly and irregularly heated; while the steam cools in its steam space
rather than is heated, that being the coldest part of the boiler, whereas it should
be the hottest.
Again, returning to the fire:-In order that the concentrated impacts of heat
may not be absolutely destructive, it is necessary to spread out the fire over
a large area, fire it with great care and skill, and leave large and to a great
extent otherwise needless vacant spaces above and around the fire to prevent too
fierce attack by it upon the working substance; further increasing bulk and
massiveness.
So I might go on and trace the calamitous effect of the basic error stated
through the entire mechanism, especially in connection with the prevalent idea that
water is the only convenient, or a specially convenient, working substance, which is
certainly sound enough under present conditions of practice, and under any
conditions for non-condensing engines, but which has no other logical foundation
for condensing engines, when traced back to its starting point, than the basic error
referred to.
It is believed that, in the light of a larger knowledge and at no distant day these
methods will be looked back upon with wonder as needlessly barbaric, absurd and
crude; as much so both in nature and degree as the old Newcomen process of using
the same chamber both as a working engine and a condenser. In fact, the modifica-
tion of process covered by this application bears a close analogy to that by which
the modern steam engine process was evolved from the New comen or pre-Watt
process, each consisting simply in a differentiation of process by which additional
steps are introduced to effect the same result. The essentials of the respective
basic processes may thus be stated.
The old pre-Watt process employed three elements.
1. A furnace and boiler combined. 2. A passage for working substance, and
3. A working engine and condenser combined.
Watt in 1769 differentiated this process by separating the engine and condenser,
and thus increased the conversion efficiency of the steam from one per cent. to about
five per cent., which one hundred and twenty-five years of effort in perfecting details
has since expanded to a maximum efficiency of about fifteen per cent..
The process
thus obtained and still in universal use employs the following elements.
1. A furnace and boiler combined. 2. A passage for working substance.
orking engine. 4. A passage for the exhaust. 5. A condenser voiding
combined heat and working substance externally.
In the process of pressure generation forming a part of the present invention,
however, this Watt process is differentiated still further by separating the furnace
and boiler, as illustrated in the diagram, Figure 1 of the drawings, and employing
the following seven elements. 1. A heater H. 2. A passage V for circulating fluid
from heater to boiler and preferably also for return to boiler. 3. A boiler B to
which no fire is applied. 4. A passage P from boiler to engine. 5. A working
engine E. 6. A passage P¹ for the exhaust. 7. A condenser C.
It is obvious that this process, as well as the pre-Watt and Watt processes may
be abbreviated at the expense of economy by omitting the condensing step. The
two latter processes then become identical, each alike giving the modern non-
condensing engine process, but the pre-Watt process never was in fact so
abbreviated.
Before describing the details of my new process of pressure generation, I will
describe the general method of applying it to existing forms of steam engines, and
the advantages which result therefrom.
I will take the locomotive, as one of the most unpromising examples of modern
engines for a modification of process. I will regard and treat its two engines as
one; that making the case still less favorable. Let, then, all fire be removed
from the fire box and placed in a separate receptacle, say on the tender. Let the
grate be closed and made water tight; let suitable baffle plates be put into the

page_text: abandoned fire box and at the ends of the tubes so as to promote an effective
circulation, and let the first and greatest heat be applied at the top of the boiler
and not the bottom; let hot paraffine oil or hot water under pressure be
circulated from the fire box through the boiler as the boiler's source of heat, and
by suitable regulating appliances, manual or automatic, let the oil be heated to
some approximately fixed point, say to 355° C. (671° F.), and cooled before
returning to the heater down to the boiler temperature or any desired point above
it. Let the engine be working high pressure, as usual, between 100° and 185° C.
(212° and 365° F.), corresponding to steam at 11.2 and 1 atmosphere (164 lbs.
and 14-7 lbs. per square inch) absolute pressure. These conditions only require
that the mass per stroke of the circulating fluid shall be about 3.87 times the mass
of water evaporated per stroke (or 9-68 times, for specific heat 0-4) implying an
almost imperceptible speed of circulation.
Figure 2 of the drawings shows to a rude vertical scale of temperature the
thermal conditions then obtaining, in which His the heater on the tender, and a the
engine working nor-condensing between T¹ and T¹a. The arrows show the path
of the circulating fluid, which merely serves to convey heat to the steam, not to
bring any exhaust heat back. At the temperature and point T the circulating
fluid enters the boilers; is therein cooled through 255° C. down to the steam
temperature, and then returns back to the heater to he heated up again to T.
It is now easily seen that we have thereby enormously increased the thermal
efficiency of the boiler. A liquid at 355° C. (671° F.) is in contact with the fire
box and tubes, this being hotter than the most exposed points of the inner face of
the fire box ever are with radiant heat at 1500° to 2000° C. (2732° to 3632° F.)
acting directly upon them, as shown by the fact that lead safety plugs melting
considerably below 355° C. (671° F.) do not melt in it. But every part of the
heating surface, both fire-box and tubes, now is or may be exposed to this same
temperature and liquid contact. As illustrated in Figure 2 the inean thermal head
for the whole heating surface is only half as great as this; but as hot water or oil
is from 20 to 50 times as effective a heating medium as air with a given surface
and a given thermal head, we have then an enormous surplus of heating power.
Our greatest heat being applied at the top our greatest steain generation is there
and there is no longer either necessity for or tendency to interior circulation.
But our metal surfaces may now be bright instead of dull, again greatly
increasing their heat transmitting capacity. We may also run heating tubes
through our steam space, and thus not only dry, but highly super-heat our steam.
We have no longer any sensible temperature strains. We can dispense with nearly
all of the water in the boiler, which has been put there only to receive and
equalize heat impacts which no longer exist, and to maintain a circulation which no
longer is needed. Both for this reason and because of our enormous excess of
heat supply, we can make our boiler much smaller. We also need no extra
thickness as a guard against explosions. We can also use much thinner and
smaller tubes, and so reduce our boiler still smaller, and reduce the thermal bead,
which is of great importance in some applications of the process. We need no
longer any space whatever for the fire box. The super-heating of the steam
alone, which is a natural result of the above process of steam generation, is likely
to reduce greatly or even avoid altogether the customary excess of 30 to 50 per
cent. in actual steam consumption over what the indicator cards call for. Every
condition is improved.
Our heater on the tender also works under improved conditions. The grate and
its containing box may be smaller and the fire correspondingly deeper. It may be
contained in a plain iron box, which does not attempt to resist temperature strains,
and so does not deteriorate under them. The surrounding liquid is below its
boiling point; consequently it generates no steam, and consequently we may use
for it any kind of cheap metallic surfaces which may safely be brought quite close
to the fire. The gases of combustion may be carried in close contact with these
metallic surfaces and their extension for some distance at the cool end, and thus be

page_text: much cooled down before discharge. The irregularities of temperature which
necessarily result from using the same surfaces alternately and irregularly for
heating, evaporating and super-heating, with their very different rates of heat
absorption, no longer exist; while the irregular heat impacts which we cannot
avoid in a fire box do no harm to such surfaces as described, which are free to
expand and contract. Our exhaust steam may still be used to cause artificial
draft, but by placing a thermostat in the circulating fluid, we may regulate
precisely the air supply which we allow to enter the fire, so as to produce just
enough heat and no more; a method of regulation which we cannot use when
the heated substance is the steam producing liquid itself, which does not change
in temperature with the quantity of heat supplied, after its working pressure has
once been reached.
It will now be obvious also that, having greatly reduced the necessary size of
our boiler, we may move back our heater from the tender to its usual place on the
engine and still preserve all the conditions with the heater on the tender. The
dissociation of boiler and fire-box, as above explained, refers only to thermal
conditions and does not forbid that they be mechanically contiguous. We have
simply to cut off the present fire-box and its heating surface bodily, put a much
smaller plain box for a heater in its place, and we still have left, in the barrel of
the boiler only, many times more steam space and heating surface than we have
any use for. Therefore, reducing our boiler to its required dimensions only, we
have plenty of spare space and weight for an air cooler or a condenser if we choose
to add one. All this has been accomplished under the most unfavorable conditions,
allowing for only one engine. With two or more engines to run we can do much
better in a variety of ways, as illustrated in Figures 3 to 7 of the drawings, and as
will be explained hereafter.
The preceding is regarded as sufficient to establish the generality of the principle
that the new process of pressure generation to be described, as applied to steam
generation, by making practical the use of a circulating fluid as the thermal
connection between fire and boiler, is a direct advantage to the simplest engine
processes, in addition to opening an easy road to further and greater modifications
of process.
I now proceed to describe the improved process of pressure generation, since its
principle and advantages only have been so far explained, and not its limitations,
which include the use of some or all of certain regulatory and other adjuncts
according to the conditions of use of the process, which adjuncts will now be
described.
In the first place, if the circulating fluid be a liquid, an expansion tank or its
equivalent must be used, since all fluids expand when heated with irresistible force,
and since the circulating pipes should at all times be full of fluid. It is then
theoretically possible, by providing circulating passages of immense strength, such
as can resist any extreme of vapor pressure which any fire can create, and by
substituting great vigilance for automatic regulation, to circulate a heat-conveying
liquid between an ordinary unregulated fire and an ordinary type of boiler, and
realize some of the advantages which have been described, but for practical results
from the process, except possibly in special applications, whether the circulating
fluid be a liquid or a gas, it must include one or more of the following features,
and to realize its highest advantages it should ordinarily include them all. These
adjuncts are arranged in their logical sequence in the process.
A. Regulation of the maximum temperature of the circulating fluid, that is, the
temperature of the circulating fluid as it passes to the boiler.
B. Regulation of the volume of the circulating fluid so as to keep it sensibly
constant at all temperatures.
C. Application of the circulating fluid to the working substance in such a manner
as to produce and utilize differential temperatures within the boiler, as below
explained.
i.
D. Regulation of the minimum temperature of the circulating fluid, that is the

page_text: tempera
which the circulating nuid 19 cooled in the boiler, preferably by
controlling the speed of circulation.
E. Regulation of the volume of working substance in the boiler so as to keep it
sensibly constant.
F. Regulation of the degree of pressure which can exist in the boiler.
Most of these adjuncts may be quite simply effected, and by different means.
The appliances which, as a rule, I deem preferable, are given below, but I limit
myself to no particular form of these appliances, as the process may be adapted to
the use of many different forms. I proceed to consider them in order.
Adjunct A. Regulation of the Maximum Temperature of the Circulating Fluid.
By this I mean the regulation of the temperature of the circulating fluid on the
hot side, that is, as it passes to the boiler or boilers, which is its maximum. This
is the most essential element in respect to safety of the apparatus when the fluid
is heated by the direct action of fire. Otherwise all the passages must be of
immense strength and thickness, since the volume of the circulating fluid is small
and its capacity for absorbing heat also small because of the lack of any
vaporization. Therefore, without regulation of the temperature imparted, the
pressure within the pipes is liable to rise, at any time when rapid withdrawal of
heat ceases, very nearly to that due to the temperature of combustion, which is
several hundred atmospheres with any probable circulating fluid. Of course any
danger of explosion from such pressure may be guarded against by a suitable safety
valve, which in any case should be added as an additional precaution, but this
involves loss of fluid from the circulating pipes and consequent disabling of the
apparatus. It should exist only as an additional and independent precaution
which is very rarely called into action, and never in normal working. The only
proper normal method of regulation is that the rate of imparting heat to the
circulating fluid shall instantly decrease when the temperature or pressure within it
reaches a certain point.
Various methods of securing this result may be used and it matters not what
particular method be chosen, and each may he brought into action either by the
temperature or by the pressure of the circulating fluid through appropriate
thermostats, valves or diaphragms. I confine myself to no particular method, but
one or more attachments for this purpose are preferably used in all cases, and
should come into action before the circulating pressures reach such a point as to
open the circulation safety valve. This becomes especially important when the
circulating fluid is water circulated under pressure to raise its boiling point, as
above described, and in most cases it is likely to be thus circulated under heavy
pressures, if used at all, in order to get a greater thermal range.
For the regulation of the maximum temperature of the circulating fluid, three
general methods are possible, which are independent of each other and may be
effected by different means, and which preferably are all used.
These are:
1. Regulation of the air supply. 2. Regulation of the fuel supply. 3. Waste of
heat after combustion. These will be considered in order.
Regulation of Air Supply. Inasmuch as the circulating fluid can practically
store no heat, nor the boiler either, when properly designed, as will be seen
hereafter, the main reliance for economical combustion must be on direct control
of the rate of combustion through the air supply or the fuel supply, or preferably
both.
The air supply can be regulated automatically with great exactitude by making
the heater perfectly air tight, or as nearly so as may be, and providing two openings
for air supply, one of which admits air below the grate to support combustion, and
the other of which admits air above the grate, in part to perfect combustion to the
extent that the nature of the fuel makes necessary but chiefly to check combustion
when necessary, by admitting air above the fire so as to destroy the draft
through it as well as to cool the gases of combustion.
To this end, the opening below the giate should be of such size as to admit all
the air needed for good combustion at the most rapid rate when full open, and no

page_text: more.
It should be controlled by any simple valve, preferably a plain flap valve
which closes completely when the temperature or pressure of the circulation
reaches a desired working maximum; and this should be the first regulatory
adjunct to act.
The opening or openings above the grate should also be controlled by some flap
or other valve which never closes the opening completely if air above the fire is a
necessity for good combustion, but which otherwise may be normally closed.
Before heat begins to be wasted as hereafter described, however, this valve should
open pretty widely, since it has the double effect of checking the production of
heat as well as getting rid of it wastefully, and thus is more economical.
Regulation of Fuel Supply. With any form of liquid, gaseous or pulverized
solid fuel, this is very easily effected by a valve acting concurrently with that
controlling the air supply for combustion.
It should therefore in most cases be
mechanically a part of the air supply valve, and in all cases may and should be
actuated by a common regulative connection, so as to be synchronous in its action.
I contemplate the use of such gaseous or pulverized fuels so far as possible, for the
very reason that the supply is so easily regulated.
When coal in solid form is used as fuel, such direct regulation is not possible,
but in practical effect it may be closely approached. I recommend in all cases
that the grate be given an adjustable and automatic slow rocking or rotating
motion, so that the fires may keep themselves in good order with a minimum of
attention. It is far more important to do this than with the now usual processes
of steam generation. These last are carried on under such dangerous and
unfavorable conditions at best that constant skilled attention is required anyway.
My aim in developing this process has been to utilize to the fullest extent its
inherent advantage of being naturally safe and self-regulative.
Therefore I recommend not only that this mechanical rotating or rocking action
of the grate be always obtained, which may be done by a suitable connection from
any moving part, but that it be made automatically variable according to the
temperature or pressure of the circulating fluid, preferably by a connection with
the same regulator which controls the air supply, in such a manner that all grate
motion ceases, or at least is diminished, whenever the circulating temperatures
begin to rise above the desired maximum. It is easier to stop the motion altogether
than merely to diminish it, since the first requires only some simple disconnecting
device actuated by the thermostat or pressure device while the second requires
a change of some leverage. Therefore, instead of aiming at a continuous through
variable movement, the motion should for convenience be intermittent but
comparatively vigorous when it occurs. It should in any case be slow, however,
in order to give its effect time to show in the temperatures before it goes
too far.
Thus regulatory adjunct becomes especially desirable when the fuel used is
anthracite. In that case the "base burner" principle, under which the fire is fed
continuously by a magazine of fuel above it, will ordinarily give the best results,
and if this be combined with regulated movement of the grate, the fire may be
kept for many hours together in just the condition required by the demand for
heat, whether regular or irregular, without any further attention than to ensure
that the fuel magazine is not exhausted.
Waste of Heat after Combustion. There are four obvious efficient ways of
effecting this end, all of which may be used, and which are preferably brought into
action in the following order :-1. Opening a direct escape for the gases of com-
bustion so that their heat is wasted. 2. Pas-ing the circulating fluid through a
wastelul cooler after it leaves the heater. 3. A temperature safety valve positively
opened. 4. A pressure safety valve opened by excess of pressure.
All these methods are wasteful, since they merely discharge to waste the
excessive heat of combustion which otherwise would be imparted to or remain in
the cinating fluid. They should, therefore, not be the primary reliance for heat
regulation any more than the safety valve, though they may be made so by

page_text: sufficient care in firing, but the regulative methods previously described, which are
checks upon the actual generation of heat, are preferably used in all cases, whether
with or without any or all of these wasteful methods. The opening of an escape
for the gases of combustion may be secured by a damper of any common form
actuated by any suitable means, such as a thermostat, and the temperature safety
valve may be placed in any suitable position upon the circulating system and
operated by any similar means. Any common or suitable form of pressure safety
valve may be used.
The wasteful cooling of the circulating fluid after it leaves the heater may best
be secured by an open evaporative tank into which the circulating fluid is directed
from the normal circulating system when the temperature rises too high, so that
the temperature of the circulating fluid in the boiler may at once be reduced
independently of any lessening of the amount of heat imparted thereto. This
change of the circulation is preferably controlled automatically by means coming
into effect before the safety valves but after the other regulative means above
stated, so as to act in case any of them should fail or all prove insufficient ;
but it is preferably controlled manually also, the special and most important
function of this feature being to cut off at once the circulating fluid from the
boiler when the boiler system is thrown out of operation, and it is then desirable
that this should be done by hand at once and independently of any other regulative
appliance. In fact, deflecting the circulation into this wasteful cooler is one of the
best ways of stopping the engine when there is no special haste to do so, since it
has the further advantage of relieving the boiler and heater of all sudden increase
of temperatures.
This change of the circulation is indicated in Figure 8, which shows in diagram
the complete circulating system with two boilers and a condenser in circuit.
Under the arrangement shown, engine E is a condensing engine working between
the boiler B, and condenser C, while E' is or may be a non-condensing engine
discharging its exhaust into the atmosphere. So far as the circulating system is
concerned it is indifferent whether E is non-condensing, or whether it has a
condenser not in circuit served by some external cooling agent. To make the
circulating system of Figure 8 conform to that of a single boiler, it is only
necessary to omit boiler B and condenser C and their connections, and run pipe V₁
directly from the lower part of boiler B to the heater H.
The normal circulation is shown in Figure 8 by the parts in full lines and is
from the heater H through the pipe V to the expansion tank, and thence through
the second pipe V to the boiler B. After circulating through this as shown by
dotted lines the circulating fluid passes by the pipe V to and through the second
boiler B', which may ordinarily contain some more volatile working substance
than B. In any case, the circulating fluid is considerably cooled by passing
through the boiler B₁ and thus is fitted to return through a condenser which
receives and condenses the exhaust steam from the engine E served by the
boiler B, and to absorb and return to heater some fraction of the otherwise wasted
heat of engine E. From the condenser C, the circulating fluid returns through the
pipe to the heater H, to be reheated and repeat its circuit. The abnormal
circulation is shown by the parts in dotted lines, and is brought into action by
shifting three way cock X, when the boilers are cut out of the circulation and the
circulating fluid passes from the tank T through the pipe V and open evaporative
tank Z back to the heater. This abnormal circulation comes into action temporarily
only for the brief periods in which withdrawal of heat through the boilers has
ceased while there has not yet been time to stop the generation of heat in the
heater, so that the excess must be dissipated unless the internal temperatures
of the system are to increase objectionably. Whenever gaseous, liquid, or
pulverized solid fuel is used, this abnormal circulating system becomes unnecessary,
because in that case the generation of heat can be stopped as suddenly as its
withdrawal.
There is another method by which this wasteful regulation may be attained,

page_text: viz. diverting the circulating fluid or a part of it from the heater, or from the
hottest part of the heater, but on account of obvious mechanical and economical
difficulties, and especially the importance of protecting all parts of the heater
against overheating, it will probably not be found desirable to use it.
It is obvious that many different means may be used for securing regulation of
the maximum temperature by some or all the methods above pointed out, and that
either thermostatic or pressure regulation may be used. As between thermostatic
and pressure regulation, however, I prefer the former, since a thermostat may
Whichever
be made so simple and yet so positive and certain in its action.
be used, however, we may, by a single thermostat or regulator, control all the
following regulative features so as to act at successive small increments of
temperature or pressure.
1. Decrease the fuel supply or stop the grate shaker. 2. Shut off air supply
below grate. 3. Admit air above grate. 4. Discharge hot gases wastefully.
5. Divert the circulating fluid into an evaporative tank for wasting heat. 6. Open.
positively some relief valve.
It is better that the positive action of a proper thermostat should be relied on to-
open a safety valve rather than internal pressure, because the thermostat acts or
may act with practically resistless power while it is almost impossible for it to
get out of order. Nevertheless, as it is conceivable that it might fail, an independent
pressure safety valve of the usual type should be added.
By these six methods, together with a pressure safety valve, we may have
perfect regulation of maximum temperature, and at all times in the most economical
way which is adequate for the needs of the moment. As they are all so simply
attained there is no motive for omitting any one of them. Nevertheless, as each
one of them is independently effective, any one or more of them may be used
without the others and with a little more care and risk may be sufficiently effective
aud but little more wasteful.
Adjunct B. Regulation of Volume of Circulating Fluid. The circulation may
be effected in part by the natural action of the difference in gravity of hot and
cold fluids, as outlined in Figure 8, where the expansion tank T is at the top of the
system and the heater H at the bottom. By an old and well-known process it is
only necessary that the expansion tank shall thus be the highest point on the
system and the heater the lowest or nearly the lowest, to have quite a rapid
natural circulation begiu under the conditions sketched and continue so long as
beat is supplied in H and abstracted in some considerable quantities in B or
elsewhere on the circuit HV TV BV B V CV₁ H. The rapidity of natural
circulation may be increased by elevating the boiler and tank T, and this natural
circulation alone may nearly or quite suffice if the circulating passages be made
large enough; but for reasons given more fully below a high speed through small
passages gives better evaporative duty than a low speed through large passages,
and hence a circulating pump is nearly always expedient, even with only one
boiler in circuit, and still more when there are several boilers, and perhaps several
condensers also.
If the expansion tank has only a moderate elevation the circulation will be
wholly liquid, or unmixed with vapour, only so long as the liquid in the tank T
stands at or near to the level of the hot intake. Thereafter, unless there be a
circulating pump and the engine is in motion, it will only be continued by the
generation of steam in the heater, which is objectionable because no metal surfaces
exposed to the direct action of fire should be alternately bare and in contact with
liquid. Therefore it is desirable that the circulating fluid shall at all times be
maintained in a nearly constant volume, and this in starting the fires as well as
when working, though this latter is not so important.
Under these circumstances, when a moderate range only is contemplated, as
from 0° to 100° C. or less, as in most hot water heating plants, it is sufficient to fill
a small-sized tight drum about half full and rely on occasional inspection to
maintain the proper height of liquid within it. The change in the volume of

page_text: water for such a range is only about 4 per cent. But when temperatures as high
as 400° C. (752° F.) or more are contemplated, the change in volume is greatly
more than in proportion, being nearly one-third, and moreover, most of the oils
expand with heat about twice as much as water, so that a very great change of
volume must then be provided for.
This may be done either by using a very large expansion tank or by providing
means for regulating with some exactitude the level of liquid within it. If the first
expedient be resorted to, the tank should have for water an interior volume of
about two-thirds of the total volume of the liquid circulation, in order that there
may be some liquid in the tank when it is coldest, and that it may not be more
than half full when it is hottest. This is the simplest expedient, and in order
that it may be feasible, it is desirable that the volume of the circulating fluid
should be kept at its minimum by using no unnecessary lengths or sizes of
circulating passages.
But the expansion tank may be made much smaller and the volume of circulating
fluid kept constant regardless of temperature or oversight, which is highly desirable,
by providing a separate storage tank of ample capacity, which yet need not be
great, at some convenient point, preferably higher than the expansion tank, and
connecting it therewith in such manner that when the expansion tank is mine than
about half full, liquid flows from it to the storage tank, and when it is less than
half full liquid flows into it from the storage tank.
This may best be effected by having inside the expansion tank a float of some
considerable size and power which floats about half immersed, so that it may act
with about equal effect by its gravity downwards or by its flotation upwards.
When the liquid falls too low this float opens a valve which equalizes steam
pressure between the expansion and storage tank, and so permits hq id to flow by
gravity or otherwise from the latter to the former through pipe connection
between the bottoms of the two tanks, which pipe should be provided with a check
valve against any undesired return current. After sufficient liquid has thus been
admitted the float will rise and close the valve, leaving the steam admitted to the
storage tank to condense therein by natural radiation either producing a vacuum or
restoring atmospheric pressure as desired. If the liquid rises too high, it can only
do so because it is expanding from heat, which means that there is or always may
be, by having a trifling percentage of some more volatile ingredient in the circulating
fluid, some small pressure at least in the expansion tank. Therefore, all that the
float need do is to open a valve in the bottom which closes a pipe leading to the
storage tank and the internal pressure will drive the surplus liquid out directly.
Both of these valves may and should be quite small, since the changes of volume
should take place quite slowly. Therefore, the work thrown on the float is very
light; so light that the float may be entirely dispensed with and the gravity of
the contained liquid alone used to actuate the valves, by making them sufficiently
delicate. But this would be inexpedient. Temperatures or pressures cannot be used
to effect this regulation for obvious reasons, but the mechanical details may be
greatly varied.
I attach considerable importance to this regulative adjunct. To use the process
in the best way we must deal with high liquid temperatures, implying great
changes of liquid volume. By the aid of this adjunct, nevertheless, we may use
quite a small expansion tank; we may be sure that it is just full enough and not
too full under all conditions and without any manual regulations, and we may
put the storage tank at any distance we please from the expansion tank, connecting
the two by two small pipes, so that it will not be in the way. It is not even
necessary, though it will usually be expedient, that the storage tank shall be
higher than the expansion tank, since some slight and constant pressure may be
substituted for gravity.
Adjunct C. Boiler Process. A circulating fluil which is otherwise properly
handled may be used with great advantage with any kind of boiler, as we have
seen, since we may leave the boiler otherwise the same and get improved conditions

page_text: for steam generation and a far greater steam-supplying capacity without other
mechanical change than substituting a circulating Huid for fire as the heating
agent.
As above stated, however, the circulating fluid should be applied, first, to the
hotter parts and then to the colder parts of the working substance, being passed
downward from top to bottom of the pressure generator, instead of applying the
heat first to the bottom of the working substance, as at present. The difference
between the two cases, and the proper functional management of the circulating
fluid may be most clearly shown by taking a simple type of boiler originally
designed for fire, say a vertical tubular, though it matters not what type be chosen,
and showing how such a boiler may best be adapted to the use of a circulating
fluid. Expressed in the fewest possible words the proper method is to enter the
circulating fluid hot through the passage which before was the uptake or chimney,
and then pass it downward through the tubes in which the gases before went
upward, whence it goes much cooled into the fire box which was before the source
of heat, and thence through the grate, thus directly reversing the usual currents
and comparative temperatures. In every sort of boiler the circulating fluid should
enter at the top, thence work its way down more or less circuitously and pass out
cooled at the bottom. In the vertical tubular boiler this descent is direct through
passages which already occupy both the steam space and the water space.
horizontal tubular boiler the descent is properly in horizontal zig-zags and there are
no tubes in the steam space, which should accordingly be added for the best
results.
In a
In either case the need for circulation has vanished and the tendency to
circulation has been largely reduced. The need for circulation resulted only
from the intense heats of the fire and the generation of most of the steam at the
bottom of the boiler. The tendency to circulation has been decreased, as the most
of the steam is now generated near the top and none near the bottom, thus avoiding
largely the mechanical action of the rising steam. Some tendency to circulation
still remains, however, owing to the unequal distribution of heat in different parts
of the boiler, which is increased largely by the side spaces left cold intentionally
to provide passages for downward circulation. It is important that all tendency to
circulation be eliminated and circulation prevented, and I secure this result by the
uniform distribution and close spacing of the heating surfaces. By uniform
distribution is meant such distribution of the heating surfaces that all of
the vertical columns into which the water in the boiler may be conceived to be
divided, between such heating surfaces and between the heating surfaces and the
boiler shell, shall receive substantially the same amount of heat and be of the same
mean temperature and density, and no cold spaces be left for downward circulation
as in the boilers now in use. The distribution of the space between the heating
surfaces and between the heating surfaces and boiler shell will depend upon the
nature and size of the heating surfaces employed. If tubes be used and they are
of the same size throughout the boiler, the spacing will be equal, but the spacing
may and preferably should increase somewhat with the size of the tubes, if different
sized tubes be used. By closely spaced is meant that the heating surfaces must be
spaced at such distances apart as to avoid the formation of any cold inter-spaces
through which downward circulation may be set up. If tubes be used, the requisite
spacing will depend somewhat upon their size and the intensity of the heating
action, the smaller the tubes and the lower the intensity the closer the spacing
required. The effect of this construction is that the water is at differential
temperatures and densities throughout in horizontal layers, lightest at the top and
heaviest at the bottom, and, therefore, actively resists and prevents any circulation
which the steam generation might otherwise cause.
This being the case, it will be easily seen why any type of fire boiler is needlessly
bulky and clumsy for use with circulating fluids, and why the continued use of such
types would involve great and needless sacrifice. In the first place, as we have no
need to provide for circulation and as our heating surfaces never rise above or fall

page_text: below an externally fixed temperature we neither gain nor lose dynamically by
having more liquid in the boiler than is needed to give the desired area of liquid
contact with our heating surfaces. As we gain a mechanical advantage by reducing
the contained quantities we should do so. We need no large liquid mass to receive
irregular heat impacts because we have none. We need none to prevent excessive
steam generation at particular points or moments, because our steam generation, if
excessive, is continuously and uniformly so and not affected by interior volume, so
that it must be controlled in other ways. As no interior circulation is wanted and
none will occur, however widely spaced the tubes within the limits defined, we neeil
no wide spacing of tubes.
Therefore the tubes may be and preferably are very closely spaced, whatever
their size, and no more liquid than is needed to give contact with them need be
enclosed. There is indeed one small advantage from having a large volume of
contained liquid, that it serves in some degree as a reserve of power. But this ena
is better attained ordinarily by the thermostatic regulation of the fires. As
economy requires that they be not pushed very hard in regular working they will
respond instantly and automatically to a considerable extra demand under the
conditions of this process. A still more important end is or may be secured by
the construction explained, which carries the heating and heated substances in
opposing currents past each other, and so introduces differential temperatures
within the chamber: viz. that it reduces the necessary mean thermal head.
reduction of the thermal head is of especial importance in the complete process to be
hereafter described, and will be more fully explained later.
This
With two inch
But the tubes no longer need to be large or thick to let gases of combustion
through freely, or to resist temperature strains or abrasion of cinders. Therefore
they should be quite small, since the liquid at slow speed flows through small tubes
equally well and the weight of the tubes per square foot of surface varies directly
with the diameter, and the heating area per cubic foot of boiler inversely therewith.
Therefore we need twice as large and heavy a boiler with one-half inch tubes as we
do with one-fourth inch and proportionately for other diameters.
tubes the boiler is increased eight fold over one-fourth inch tubes. It is even then
so small that the larger sizes may often be usefully employed, and perhaps longer
experience will indicate that larger tubes than I now favor are preferable, but so
far as I yet know one-fourth inch copper tubes are more suitable for any size of
boilers than larger tubes, and these tubes will preferably be very thin for the
reduction of the thermal head, as will be fully described hereafter in connection
with the complete engine process. With tubes of this size the boiler may be, as
already stated, so small that it may more properly be considered as a mere
enlargement of the feed pipe in which water is turned into steam as it moves along
by passing between evenly hot surfaces at a fixed rate; since as much as 100 H.P.
of steam power may be continuously and economically produced per cubic foot of
total boiler volume, as shown more fully hereafter among mechanical details.
Nevertheless it will often be expedient to attempt such very high duty, for
reasons explained at the close of the description of the next adjunct, D.
It follows from these facts that the boiler surfaces need not be tubes at all.
Instead, they may, and preferably will, be a mass of thin flat plates, closely spaced
and indented or corrugated so as to keep their spacing against whichever fluid is under
the greatest pressure, whether the circulating or the working substance. Such a
boiler will be fully described hereafter. In any case, the boiler will ordinarily
give the best results when from two-thirds to four-fifths full of liquid, and it is
better to have a considerable area of heating surface, perhaps 10 to 15 per cent. of
the whole, devoted to superheating uses alone. The possibility of very highly
superheating without risk, or any special appliances therefor, is one of the greatest
advantages of the use of my process.
As we have no need for any steam space beyond what is required for generating
and superheating the steam it follows from all that has preceded that the best
boiler for use with a circulating fluid will consist of a mass of thin heating surfaces

page_text: "
filling "steam space and "water space" alike, without any distinction between
them, with no greater total bulk that is needed to ensure enough heating surface; with
the circulating fluid entering hot at the top and working its way downward to the
bottom, and with the working substance entering cold at the bottom and leaving
hot at the top. Other details may be varied at pleasure within wide limits, as
also the character of the heating surfaces, but the character and arrangement of
surfaces described will be found to secure many advantages.
The principle that heat applied to a vaporizing substance under pressure, should
always be most intense at the top and coldest at the bottom is one of general
application, and the mere correction of this error, with a minimum of other
change, will always result in improved functional action, all the present commercial
forms of boilers violating this principle. The broad basis for this principle lies in
the fact that, inasmuch as all possible working substances expand with heat and
contract with cold, gravity always tends to segregate the exterior mass of working
or heated substance into horizontal layers coldest at the bottom, hottest at the top,
and when the process of heating produces and includes a change from the liquid
to the gaseous form this tendency to segregation is, of course, vastly increased and
becomes irresistible by any violence of circulation. Therefore, in order to produce
the smoothest and most efficient action of a boiler, the heating agent, whatever it
is, should act first at the top with its greatest intensity of heat, and then pass from
the top downward, or in a reverse direction to the heated substance, which should
enter cold at the bottom and leave hot at the top. The heating agent thus first
super heats, then surrenders heat with great intensity and rapidity for vaporization,
which confines that process chiefly to the immediate vicinity of the surface, its
intensity decreasing directly with the depth below the surface until at one-fifth to
one-half of the total depth of liquid vaporization practically ceases. Only when
the working substance is fed at the boiling point will it extend through the entire
depth, and then its intensity will decrease with the depth, so that three-fourths of
it will occur in the upper half of the liquid.
The heating agent having passed below this depth, all the remainder of the
liquid is still below the boiling point, and hence more efficient than it otherwise
could be for abstracting heat from the now much cooled heating agent and hence
the latter is cooled before it is discharged sensibly below the point possible, when,
as in most present types of boilers, most of the gases never encounter any liquid
below the boiling point before discharge. Heat from whatever source and however
communicated should always be supplied to a pressure generator first and hottest
at the top, and thence should be decreased in intensity by being passed downward,
cooling as it goes.
A pressure generator designed according to these methods is a reversible
mechanism, that is to say, it is only necessary to reverse the direction of the two
currents of heating and heated substance which pass through, all temperatures and
pressures remaining the same, and it becomes an equally efficient condenser or
cooler of the vapor which before it generated. This results from the fact that the
real aim in both cases is the same, that is, to transfer heat from one substance_to
another. Hence, for reasons already given, the substance which is to surrender
heat should in each case enter at or near the top and go out at or near the bottom,
while the substance which is to absorb heat should enter at or near the bottom and
go out at or near the top. When the chamber is being worked as a pressure
generator the working substance is to absorb heat and enters as a liquid from the
bottom, going out as a vapor at the top. When the same chamber is to be worked
as a condenser for the same vapor, the working substance is to surrender heat, and
The beating agent
hence euters as steam at the top and goes out at the bottom.
in each case alike flows in the reverse direction to the working substance, its
proper top and bottom temperatures remaining the same. Ordinarily the vapor
which we wish to condense is not in quite the same status as the steam which we
wish to generate and some slight mechanical difference may result from this fact,
but this is another issue, and so small a one in all ordinary cases that a well designed

page_text: pressure generator and condenser should be mere duplicates of each other, despite
the differences of pressure.
Adjunct D. Regulation of Minimum Temperature of Circulating Fluid. By this
I mean the regulation of the temperature of the circulating fluid on the cold side, that
is, as it passes from the boiler which is its minimum. This adjunct is indispensable
in some of the more complex forms of the process, with several boilers in circuit
working at different temperatures, and even in the simplest case with only one boiler
in circuit, it is always desirable. The best method of effecting this regulation is by a
thermostat, and the best method of applying the thermostat is to regulate with it
the speed of circulation, so that, if the circulating fluid is leaving the boilers too
hot, its speed may be checked, and if too cold, its speed may be increased. The
best method of doing this latter is to have a circulating pump throwing some
excess over the maximum demand for circulation and connected with this pump a
thermostatically controlled by-pass which permits a varying percentage of the
liquid pumped to circulate round and round through the by-pass and pump without
making the circuit through the heater and boiler or boilers.
If the minimum temperature be not regulated, we shall not have a constant mean
temperature within the boiler even though we have a constant maximum, and we shall
often have the circulating fluid returning to the heater so hot as to waste much heat.
It is possible to regulate the minimum temperature without controlling the epecd
of circulation. For instance, if there be a perfectly uniform withdrawal of steam,
and supply of working substance, circulating fluid which enters the boilers at a
constant maximum will leave them at a constant minimum. We may also
to vary the proportion of the boiler surface which is active by varying the arca
arrange
which is immersed in working substance. But this variation of extent of active
surface is preferably a feature of the control of the quantity or pressure of steam
generation, as explained later, when it is used at all.
The thermostat by which the speed, or volume per minute, of the circulation is
regulated I term the "cold thermostat." It should be sensitive and quick acting,
checking the circulation almost completely as soon as the circulation begins to run
too hot, as it will as soon as withdrawal of steam is checked, and opening wide as
soon as it begins to run a few degrees too cold. It should be adjustable, so that it
may be set for any desired temperature.
When the withdrawal of steam from the boiler suddenly stops, even though the
cold thermostat may promptly stop the circulation, the boiler passages will be full
of hot circulating fluid which is hotter than the contained working substance by
the amount of the transmission interval, which may in cases be as much as 100° C.
or even more. Hence, as soon as withdrawal of heat stops, the boiler temperatures
and pressures will equalize with the circulating fluid and there will be a quick rise
of pressure. The precaution which is generally preferable against this quick and
certain increase of pressure is not to use such high circulating temperatures and
large transmission intervals as to produce a dangerous pressure, even when steam
withdrawal stops, as for instance, one exceeding 30 to 40 atmospheres, which well
designed boilers of the type herein below described may easily stand.
On this
account chiefly it is not expedient to try to force a boiler up to its ultimate
capacity, which seems to vary directly with the thermal head. But in cases it may
seem necessary or expedient to do this, or excessive temperature may result from
some accident without intention. Whenever this is deemed possible it makes
regulatory adjunct E described below desirable.
Adjunct E. Regulation of Quantity of Working Substance in Boiler.
Whenever a condenser is included as part of the engine process this regulatory
adjunct may conveniently be omitted, because the working substance then works
in closed cycle and a pump of whatever type keeps the condenser nearly or
quite empty by pumping all working substance as fast as liquified back into the
boiler, thus maintaining it therein at what will be, except for possible carelessness,
a sufficiently constant level.
For the practical reason that pure feed waters are scarce and impure ones would

page_text: rapidly coat the thin and highly active surfaces which I prefer for my boilers,
I contemplate nearly always using a condenser, whether or not any considerable
vacuum is aimed at, and whether or not a supply of condensing water is available.
To this end I have devised a type of evaporative condenser, hereinafter described,
which requires no more water than would otherwise be required for feed water,
which is extremely compact, and which will readily give a considerable degree of
vacuum, if desired, and at all times enable the feed water to be used over and over,
and thus to maintain a tolerably constant water level in the boiler.
When no condenser is thus connected with the boiler, however, it is highly
important that the water level in the boilers should be regulatel to the extent of
insuring that it shall not rise above a certain level, because, should it do so, the
boiler is of such small interior capacity, and so nearly full of liquid at best, that
the irresistible force of liquid expansion may be called into action, and the boiler
ruptured. It may be so simply effected, moreover, that it may be better in all
cases of importance to regulate the water level directly, whether or not a condenser
be used. Any one of a variety of well-known mechanical devices may be used to
effect this regulation. The proper one to select depends primarily on how the
feed-pump is driven, whether directly from the engine, by a separate engine, by
electricity, or by the direct action of steam. I prefer the latter method, and the
regulating device which I deem best consists of nothing more in substance than a
little ball valve float, which, when the water level rises too high, rises and closes
the aperture through which steam escapes to work the pump, as fully described
hereafter.
Adjunct F. Regulation of the Degree of Pressure that can Exist in the
Boiler. This adjunct may best be secured by a mere water safety-valve,
through which, when the steam pressure reaches a certain excess above the
desired working pressures, just before it reaches the pressure at which the steam
safety valve is set to open, all liquid is blown out of the boiler through the feed
pipe or other suitable connection.
This liquid may either be discharged to waste, or blown back into the working
substance supply, or into the condenser. The last is preferable, if there be a
condenser. The pump, if operated by direct action of steam, will then immediately
begin to return the water to the boiler but will not be able to do so in any quantity
until the pressure falls below that at which the liquid blow-off opens, either
because of cooling or of starting the engine. When the pressure thus falls,
however, the boiler will then immediately begin to fill and if provided with
adequate pumping power, will fill up to the level at which the immersed surface
will just suffice to generate steam, at the rate at which it is being drawn off for the
time being, or to the level fixed by adjunct E.
The adjuncts above described relate particularly to the generation of the vapor
pressure. There are also certain useful results which may be secured by special
applications of the circulating fluid, which make the complete process more
economical. Among these, the two following are the most important.
The circulating fluid is particularly suitable for jacketing the engine cylinders
as now usual with steam, and it is preferably thus applied when my improved
process of pressure generation is used in connection with expansion engines. Its
chief advantages for this purpose are that it is or may be at a higher temperature
than the steam while not too high, and no provisions are required for taking care
of the water of condensation, nor for making the steam jacket steam tight, nor for
making it capable of resisting pressure, except that of the circulating fluid when
the latter is circulated under pressure.
The circulating fluid, after having subserved its function of supplying heat to
the working substance, may be used to condense the vapor of the working
substance, and thus be partially heated before its return to the heater.
With a
single boiler, there is no advantage in thus running the circulating fluid through
a condenser, unless the circulating fluid be cooled between the boiler and condenser,
since it is not cooled enough in one boiler to absorb any otherwise waste heat on

page_text: its way back to the heater. But if two boilers in circuit be used instead of one,
the second one of which should or may use a more volatile working substance than
the first, the circulating fluid will be cooled enough by the second boiler to be able
to absorb some waste heat from the engine of the first boiler. In that case the
circulating fluid would pass through a second boiler after the first, then through
the cold thermostat and then through a condenser interpolated in the cold
circulation pipe VI, as outlined in Figure 8. Of course the same advantage exists
in using the circulating fluid for condensing, if the fluid be cooled after leaving
the first boiler by its use for any other purpose than for a second boiler.
Some of the betterments of present engine processes proper, or modes of using
steam, which are made possible by the superior methods of steam generation so far
described are illustrated in Figures 2 to 7, and may be thus described.
In the ordinary engine process, the great thermal interval between the temperature
of combustion and the boiling point of water under pressure is unutilized. The
heat supply is lowered in temperature through the whole of this interval without
dynamic gain. Having our circulating fluid, however, heated to a considerably
higher point than we require for our engine a, Fig. 2, and yet at a regulated and
approximately constant temperature, and having the power to work with low
thermal heads from the construction of the boiler, it is obvious that we have in this
difference of temperature, T-T', Fig. 2, a working interval in which we may, if
we please, work one or more additional heat engines, using water or any other
liquid or gas as a working substance.
In Figure 3 is illustrated to a rude vertical scale of temperatures one way in
which we may do this, and with much advantage, since four engines are in effect
run with no greater rejection of heat than otherwise results from the use of two.
In this construction the engines a and a' are alone worked under the usual
conditions for high pressure engines, receiving at each stroke a new supply of
steam and exhausting it wastefully into the atmosphere. The engine a receives
its heat directly from the circulating fluid, in the same manner as engine a, but at
a considerably higher temperature and pressure, and compounds or transmits its
waste heat to a¹. The fourth engine a, receives its heat from the circulating
fluid indeed, but in such manner as not to finally lower its temperature, the
circulating fluid being returned into the heater one or more times after supplying
heat to the boiler of all so that its original temperature may be restored.
is thus left a sufficient thermal interval for the engine all to work in and yet void
the heat in its exhaust at such a high temperature that it may be used to do about
half the work of heating up the circulating fluid through an appropriate condenser,
and hence the engine may use any working substance in closed cycle, preferably
one of higher boiling point than water so that the working pressures due to its
temperatures may not be excessive.
There
These four engines may be arranged mechanically in any way desired, the sole
necessary condition being that the circulating passages of their boilers shall be
connected in such manner that the circulating Huid shall follow the following path,
starting from the heater:
Heater. Boiler of a¹. Back to heater to be reheated to original temperature.
Boiler of a where circulating fluid loses heat. Boiler of a where it loses more
Condenser of a where the rejected heat of engine a¹ is reabsorbed into
the circulating fluid. Heater, to be reheated and repeat circuit.
heat.
In Figure 4 is illustrated a still simpler way in which two engines may be run
with a saving of about half the heat supply of one engine. The circulating fluid
is assumed to have only half the volume or mass V per stroke in Fig. 4 that it has
in Fig. 3, so that the same quantity of heat, which is that necessary to run the
engine a, cools the circulating fluid through twice as great an altitude of temperature.
The engine a', by circulating passages not indicated on the diagram, is supplied
with heat from H. at the temperature T without permitting the circulating fluid to
be finally lowered in temperature thereby, which latter is effected by returning the
circulating fluid to the licater to be reheated to temperature T after supplying

page_text: heat for the engine a¹. After being thus reheated, however, the circulating fluid
supplies heat to the engine a and is thereby lowered in temperature to T', which is
cold enough to permit the returning circulating fluid to absorb half or more of the
exhaust of waste heat of the engine a¹ by passing through its condenser on its way
back to the heater, thus relieving the heater of this proportion of the work which
would otherwise fall upon it, with corresponding economy. The two engines
The sole
may have any desired relation to each other mechanically, as before.
requirement is that the circulating passages shall carry the circulating fluid in the
cycle described and shown.
In Figure 5, which is drawn immediately below the single engine diagram,
Figure 2, to facilitate comparison, is illustrated how, by substituting three engines
for the single engine a, each working from a little lower maximum temperature
than the preceding one, additional power may be attained under the identical
thermal conditions of Figure 2, with the sole exception that we avail ourselves
better of the thermal range open for work by actually working through a greater
portion of it, as indicated by the comparative hatched areas of Figures 2 and 5.
The hatched areas of Figure imply working the steam of the first two of its
three engines through compound cylinders whereas the hatched area of Figure 2
implies only a single cylinder, but otherwise they are the same, the quantity of
heat received and voided and the manner of doing so being essentially identical,
except that the thermal heads are smaller in Figure 5 and hence the boiler heating
surfaces must be correspondingly greater. With the types of boilers herein before
and hereinafter described heating surface is gained so cheaply and compactly that
this is no great matter.
Figures 6 and 7 show how the amount of work shown in Figures 3 and 4 may
be increased in precisely the same way as that shown in Figure 2 was increased to
that shown in Figure 5 by tripling the number of engines and boilers worked
within an identical thermal range, so as to avail ourselves more completely of our
whole thermal interval for work. In Figure 6 the cycle of the circulating fluid,
the sole rigid condition for any desired mechanical arrangement, is as follows:
Heater. Boiler of first engine a and back to heater. Boiler of second engine all
and back to heater. Boiler of third engine a¹ and back to heater. Boiler of first
engine a. Boiler of second engine a". Boiler of third engine a". Boiler of first
engine a. Boiler of second engine a. Boiler of third engine a.
Condenser of
third engine a. Condenser of second engine a¹. Condenser of first engine a¹¹,
and back to heater to repeat the circuit.
111
Figures 2 to 7 are designed to be merely illustrative and not at all to give either
the only methods or those of highest efficiency employing my improved pressure
generating process. On the contrary the details of this primary process may from
its nature be varied almost indefinitely.
There is, however, one old and well-known engine process which heretofore has
had little or no practical utility, which is raised by the application of this primary
process of pressure generation to one of much higher efficiency than any now
known, though not so high as that attained by the new series engine process above
referred to and which will hereafter be fully described. I refer to that special
type of engine process wherein an expansion heat engine of any type exhausts
into a boiler of some form wherein the heat of vaporization is used to heat and
thus generate or increase vapor pressure in some more volatile working substance
for a second engine, which second engine in its turn, exhausts or may exhaust into
another boiler wherein its otherwise waste heat is used to generate or increase
vapor pressure in some still more volatile working substance for a third engine,
and so on for any number of steps desired until the attainable temperature limits
are exceeded. This process and the engine embodying the same, sometimes called
simply the series process and engine, will hereafter be referred to as the step series
process and engine.
The effect of the proper application of this primary process of pressure generation
to this step series engine process is so important that the combined process will be

page_text: +
1
fully described as the best application of the process of pressure generation to any
known form of engine process, and this combined process forms a part of the
invention, although, as above stated, it offers less advantages than the new engine
process to be fully described hereafter.
The theoretical possibilities of this step series process have long been known and
are very great, since their limits are fixed only by the materials, and in no way by the
nature of the process itself, as is the case in the single expansion or Watt process,
which latter admits of working through a very limited temperature range only,
and admits of extension within this range only under a rapidly increasing disadvantage
from low mean pressures. Nevertheless, although these theoretical possibilities have
been of commen knowledge for more than a century, and this has resulted in
numerous attempts to utilize some of them practically, such efforts have met with
so little success that very few, if any, such engines are now in use, and the process,
as practically applied, has thus far shown but little, if any, practical utility, and is
not a factor of modern engine practice.
The failure of this process heretofore has been chiefly due to a failure to secure
and utilize small thermal heads, or differences of temperature between the heating
and heated substances, primarily in the first boiler, and secondarily in the subsequent
boilers and condensers, so that it has been impossible to provide thermal room for
the series of boilers and engines except under very disadvantageous conditions. The
cause of this difficulty is as follows:-
Modern boiler practice is based upon the radically erroneous principle of attacking
the working substance with a fierce irregular heat acting upon small massive surfaces
with a very great thermal head. This error has been extended largely by analogy
to modern condenser practice, and attempts which have been made to utilize the
step series process have copied after these defective methods, with resulting loss of
effective thermal range because of high thermal heads which have been fatal to the
usefulness of this process.
To establish a field of usefulness for the step series process, it must show
considerable advantage over a condensing single engine process, since the latter
will be the simpler mechanically. The condensing steam engine alone will readily
work down to one-third of an atmosphere absolute pressure, corresponding to
72° C. (160° F.) steam temperature. The natural cold body into which the waste
heat is voided is rarely colder than 10° to 15° C. (50° to 59° F.) and all or most of
the remaining small range between these two temperatures is necessarily consumed
to effect condensation under modern condensing conditions. There is therefore no
thermal room to add another engine below the complete single engine process, and
all that can be gained by cutting short this latter process to make room for a
second engine below it, is to secure higher mean pressures by expanding two masses
of working substance slightly instead of one mass to the utmost, and even then the
room is scant.
If we cut the first process short, we have to deduct two intervals for thermal
heads instead of one, and the loss from this additional interval, and from adding
the mechanical complexity, is greater than the gain from the higher unit pressure,
and the total temperature range which may be actually worked through is less
with the two engines than can be covered with one.
Under the conditions of current practice, therefore, there is really nothing to be
gained by adding another engine below a steam engine, and there is practically as
little room above the steam engine, since temperatures of about 350° C. (662° F.)
in the fire-box surfaces are now used and required to enable a single steam engine
to work within the range that it can well cover, that is, from about 180° C. to 72° C.
The possible theoretical efficiency within this latter thermal range is about
twenty-four per cent., but the practical difficulties of working through even the
smaller of these ranges with a single engine cuts down the efficiency in practice by
one-half or more, or to some ten to twelve per cent., the greater portion of this loss
resulting from the attempt to expand a single mass of steam through the last half
of the temperature range. It is chiefly to save this loss that efforts to utilize the

page_text: step series process have previously been directed, and these efforts have failed
chiefly on account of the loss of range resulting from the additional thermal head
required.
It will be seen that nearly two-thirds of the loss of range, 350° C. to 18.,° C.
lies in the primary process of generating the steam in the first boiler.
I avoid this loss by substituting for the now usual boiler process, the process of
generating steam by the use of a circulating fluid above described, in connection
with a boiler especially adapted to use therewith which is capable of working with
extremely small thermal heads. I am thus enabled to create a wide thermal field
for the step series process, and I utilize this by repeating in subsequent boilers the
process features of the primary boiler so as to work through these boilers also with
extremely small thermal heads. Some of the mechanical details and regulative
features preferably used in the first boiler, however, in which the circulating fluid
is preferably a liquid acted on by fire are not necessarily nor preferably repeated
in the subsequent boilers for reasons hereafter explained.
The working substance to which heat is applied by surrender from the circulating
fluid in the first boiler may be any suitable gaseous or liquid substance in which
the vapor pressure may be generated or increased with a low thermal head so as to
leave as wide a range of temperature as possible for the succeeding boilers and
engines of the step series, and by the change of pressure-generating process we
are able to operate with very small thermal heads for the following reasons:-
The circulating fluid heated by fire being preferably a liquid which is not
permitted to vaporize to any extent within the heater may be heated to temperatures
much higher than are prudent or possible in an ordinary boiler. It is preferably
carried in pipe surfaces brought close to the fire in which a high temperature is
quickly attained. By using this hot fluid only to supply heat to the boiler we
eliminate all temperature strains in the boiler by subjecting it only to a regulated
and uniform heat, so that the heating surfaces may be thin and thus provide for a
full and quick transmission of heat from the circulating fluid to the working
substance. We can therefore get a large heating surface in a small space.
We
may multiply many times the efficiency of the heating surfaces when the circulating
fluid is a liquid by securing liquid instead of gaseous contact with the heating
surface. We may radically improve the functional action of the boiler by avoiding
the necessity for and tendency to circulation of the working substance, as already
described, and may permeate the entire interior of the boiler with our heat supply,
preferably the steam space as well as the water space, by using a large number of
small closely set tubes or their equivalents, thus insuring perfectly dry and
somewhat superheated steam and also, which is very important in this process,
producing differential temperatures in horizontal strata, coldest toward the bottom,
so that the heating substance may be discharged at the bottom considerably colder
than the heated substance is discharged at the top. All sensible tendency to
foaming in the boiler being abolished it may be carried nearly full of liquid, thus
sensibly increasing the proportion of highly active surface.
By the process for generation of pressure which has been described above I thus
create a wide thermal field for the step series process, and this process and
apparatus embodying the same may be used in combination with any suitable step
series process and engine, and such a combination forms a part of the invention,.
as by the above process I am enabled to provide a wide thermal field for use by
the step series process and this forms an important advance in this art even in
connection with the existing defective methods and apparatus for utilizing this
field.
But the same general methods of heat transference provide an apparatus by
which a reduction in the thermal heads required for the secondary steps of the step
series process is secured, thus increasing very largely the number of engines that
may be introduced below the first engine, or else increasing their mean effective
thermal range. This is secured by repeating in the apparatus for carrying out the
secondary steps of the step series process the general process features of the

page_text: primary boiler, as above described, although not necessarily or preferably the detail
features, on account of the nature of exhaust steam, which is already regulated in
temperature. As condensing steam is not lowered in temperature by its surrender
of heat the entire heat of vaporization may be surrendered without any decrease
in temperature other than the slight difference which results from the decreasing
pressure, and by a proper arrangement of the boiler-condenser the effect of this
slight difference also may be eliminated, with the uct result that a very small loss
of range, 5° to 20° C. (9° to 36° F.) at most, is involved by each successive step
and engine: This reduces the loss of range involved in getting the heat into and
out of the steam to very small proportions, and thus enables us to use additional
steps freely and so avoid all need of working each engine through a wide range
and with high expansion, with the effect of heavily reducing engine bulks and
weights. In carrying out the process a single boiler-condenser for each step and
engine is preferably used to effect the heat transfer and the features of these
boiler-condensers are as follows:-
It is of especial importance in these secondary boilers that the heat transmitting
surfaces be thin and they preferably have only the thickness and range of thickness
of good stout paper, say from one-fifth to one millimeter, although it is obvious
that this thickness may be increased somewhat without great loss of efficiency.
These thin surfaces in secondary boilers not only secure the advantage of providing
a large amount of heating surface in small space, thus economizing space as well
as weight, but also aid directly toward obtaining a very small thermal head
between the temperature of the effluent hot vapor and the temperature of the
incoming exhaust steam by which said vapor is heated, and if the application or
removal of the heat or both be intermittent, the thinuess of the surfaces will
materially increase the quantity of heat which will pass during the intermittent
instants when the conditions are most favorable for transmission, and such
intermittent application and removal of the heat naturally occurs in the operation
of most engines.
The steam to be condensed should not be poured in en masse and left to distribute
itself properly by its internal pressure only, but should be conducted through a
series of passages by which it enters at the top of the boiler-condenser and
gradually works its way down to the bottom thereof, being hottest at the top and
coldest at the bottom, and thus securing the most effective conditions for
condensation and either the proper distribution of the condensing steam to the
heating surfaces or its complete condensation by less than the full surface, since
the progressive cooling of the steam of itself produces a differential pressure which
tends to force the steam forward and downward through these passages.
The liquid to be evaporated or working substance should not be discharged into
an interior open chamber and cuculated up and down, but should enter at the
bottom where the temperature is lowest, and downward circulation be prevented so
that it passes continuously upward and in close contact throughout with closely
spaced heating surfaces against which it continually impinges until it is vaporized
and superheated so far as the temperature of any portion of the entering exhaust
steam permits. It is important that circulation be prevented and this is secured
by the passage of the steam downward through the working substance, and by the
uniform distribution and close spacing of the heating surface, as already fully
described.
In this manner, by sufficiently careful design, preventing circulation, using large
heating surfaces with very close spacing, it may be insured that the final
temperature of the generated steam shall be sensibly higher than the final
temperature of the condensed liquid, and even when this result is not attained
there may be in all cases a close approach to it, thus greatly diminishing the
otherwise necessary thermal head, which is of the highest importance to the step
series process.
So different is the proper thickness and spacing of heating surfaces desirable
under my process from anything in use, that these surfaces can hardly be too

page_text: closely spaced, if the best results are to be secured, whereas the now usual process
of steam generation and of condensation as well, which depends upon circulation
of the working substance and treats the interior as a single chamber to be subjected
to uniform temperature conditions, demands in all cases quite wide spaces. If
tubes are to be used, so different are those recommended, say one-third millimeter
thick and 6 to 8 millimeters diameter, from any of present practice, that I have
found them obtainable only from manufacturers of metal pencil cases, and while it
is difficult to define the limits of thickness and size of tubes, they cannot be said
to be thin and small in the sense in which these terms are used herein unless far
thinner and smaller than any condensing tubes of current practice. In fact, the
attainment of the best results with this step series process demands that the
surfaces shall be even thinner than is commercially attainable with tubes, and for
this reason I recommend the use of corrugated or indented plates for forming the
boiler-condensers, as fully described hereafter, whether or not the same
construction be adopted for the primary boiler.
All these statements with reference to boiler-condensers for the step-series
process apply to either the boilers or condensers of the complete new series process
to be next described, with trivial exceptions, noted elsewhere.
As above stated, a single boiler-condenser is preferably used between each pair of
engines to effect the heat transfer, but this is not a necessity. In fact it is
sometimes a mechanical convenience to dissociate the engines, and it may be
convenient to carry off some of the heat between any two steps of the process for
some other use. It is obvious that by the use of the circulating fluid process above
described we may substitute for a single boiler-condenser two such chambers and
connect the two by a circulating fluid, or preferably, in some cases, by an
intermediate vaporizing substance. In this case the steam to be condensed will be
discharged into the first chamber, which is merely a condenser, and there heat the
circulating fluid which passes to the second chamber, which is merely a pressure
generator and in which the circulating fluid surrenders its heat to the second
working substance, securing the same results as if the steam heat had been
applied to the same substance directly in the first chamber. Two duplicate
chambers are thus required in place of one, but they are small, cheap and light,
and a very slight mechanical advantage may suffice to warrant this duplication.
Of course the exhaust steam may be piped directly for a considerable distance
and the additional chamber saved, but by transfer the heat may always be carried
more compactly and perhaps in a substance more suited for some incidental
intermediary use. It will be understood, therefore, that two chambers, as above
described, may he used in place of and as the equivalent of a single boiler-
condenser.
I now proceed to describe the complete series engine process above referred to,
which is technically a particular case under the general process of generating
pressure first above described, but whereas this general process relates primarily to the
generation of vapour pressure, and is independent of the particular use which may
be made of that pressure or of the methods of handling it, the particular process
now to be described derives its chief economic importance from the combination of
the three processes of generating, utilizing and destroying or condensing vapours
in a peculiar way.
An extended description of the theory and various methods of practising the
series engine process will be necessary to a correct and full understanding of the
same and of the apparatus by which it may be carried out, but, on account of
the wide departure made by the invention from the present art, it is thought
best to describe a simple form of the process in connection with diagrams
illustrating the same before proceeding to such extended description, reference
being had to Figures 9 to 18 of the accompanying drawings as follows:
Figure 9 is a diagram illustrating the principle of the process, as applied to
series engine consisting of seven engines. Figure 10 is a diagram of the
temperature conditions in such a series engine. Figure 11 is a typical indicator
D

page_text: .
diagram showing the preferred method of operating the separate engines in
series. Figure 12 is a diagram illustrating a development employing a plurality
of series operating at decreasing temperatures. Figure 13 is a temperature
diagram of the same. Figure 14 is a temperature diagram showing another
method of applying the same principle. Figure 15 is a diagram illustrating the
principle of cold interval engines. Figure 16 is a temperature diagram of the
same. Figure 17 is a diagram illustrating the principle of combined series,
cold interval, hot interval and heating engines. Figure 18 is a temperature
diagram of the same.
The principle of the series engine process will now be described in connection
with Figures 9 to 11.
Let a, b, c, d, e, f, g, Figure 9, be any kind of heat engines working by the
expansive force of a working substance. Let them have either high or low
conversion efficiency, separately considered. Let them be either of the same or
different size or type, or some of each, and let them use either the same or
different working substances.
Let each of these engines work within itself in a closed cycle between its
boilers B, Bb, etc. its condensers, C₁ Cы, etc. and its cylinders or other
engines a, b, c, clc.; that is, let steam supplied from the boilers B, etc. be expanded
in the cylinder, thence exhausted into the condensers C, etc. and there condensed,
being returned again in liquid form by a pump to the boilers B, etc. to repeat
the cycle.
Let these separate boilers B, B. etc. be arranged as to their interior passages
for the heating substance so as to form for it a continuous passage-way from end
to end of the series, and let the boilers be designed to receive beat only from this
heating substance and not directly from a fire or other source of heat, which latter
is contained only in a heater H, apart from the boilers.
In thermal conditions, a series of boilers thus arranged bears a close functional
resemblance to an ordinary tubular boiler having the barrel very much elongated
and divided by sundry watertight partitions into so many different and separate
boilers having also the "fire box or heater H at one end as usual, but without
any of the usual fire box heating surface for evaporative purposes. It is evident
that each one of these separate boilers, B, to Bg, may be used to evaporate either
the same or a different working substance, but that the conditions naturally tend
to a continuously decreasing scale of temperature as the heater is departed from,
and that, if the same working substance be used throughout, the pressures will
tend to be lowest at the cold end, and to increase continually as the heater is
approached. On the other hand, if highly volatile working substances be used
in B, etc. at the cold end, and highly unvolatile substances in Bg, etc. at the bot
end, and we have a sufficient range of choice, we may, if we please, eo arrange
the working substances as to have in all of a long series of these boilers a nearly
constant vapor pressure despite very material differences of temperature. Each
one of these separate chambers, B₁ to Bg, is therefore functionally a separate
boiler, though thermally all may be considered to be in a certain sense parts of the
same compound boiler.
Similarly, let all of the separate condensers, C., C., etc., be arranged as to their
interior passages for a cooling substance which does all the condensing work,
so as to form for this substance a continuous passage-way from end to end of
the condenser series, similar in all essential respects to the boilers, but having
the current through it in the reverse direction; .e., toward the heater instead
of away from it. It is evident that under these conditions the condensers as
well as the boilers will grow hotter toward the heater; i.e., the hottest
condenser will be opposite the hottest boiler, and the coldest opposite the coldest
boiler.
Let the passages through the condenser circuit and the passages through the
boiler circuit be connected together at the "hot end" in a heater H, where heat
can be supplied, and let them be connected together at the "cold end in a
"

page_text: cooler, C, Figure 9, where a certain amount of heat can be abstracted; thus
forming a closed circulating circuit exterior to the several engines and including
in order the condensers, heater, boilers, cooler, and condensers again, as indicated
by the arrows of Figures 9 and 10.
=
Let a heat conveying substance or "circulating fluid," of specific heat 1.0 always
assumed unless otherwise stated, and of mass per stroke:
V, be continuously
circulating through this exterior circuit in a closed cycle and in the direction of
the arrows of Figures 9 and 10, as follows: the cycle of temperatures being as
indicated graphically in Figure 10 Issuing from the cooler C at the nearest
convenient approach to the natural minimum temperature for the time being, T.
which is the only thermal point in the process fixed by external conditions, and
therefore, as well as for other reasons, the natural starting point, the mass V
passes through condenser C. Figure 9, where it receives the heat due to the
condensation of one stroke of exhaust steam, being raised in temperature thereby
from T' to T in practice, 2° to 40° C., according to the size of the engine and
mass V. Moving continuously on at uniform speed, it then passes through the
next condenser C, where it receives the exhaust heat from one stroke of engine 1,
which works between temperatures 2° to 40° C. higher than engine a, to enable it
to do so. The mass V is thereby still further raised in temperature from T to Tb.
So it goes on through all the condensers in series, or "cold circuit," having been
thereby raised in temperature to T, or enough to absorb the entire heat rejected
by one stroke of all the engines.
:
The circulating fluid thus receives V (T-T) units of heat, which may be 85 to
95 per cent. of the heat originally supplied to one stroke of all the engines, the
remaining 15 to 5 per cent. having been converted into work. It will be seen later
that it is not really economical to seek for the highest possible percentage of heat
conversion from each of these several engines; rather, the engine as a whole i-
more economical if the several cylinders have a relatively late cut-off, and conse-
quently a low percentage of heat converted into work.
The mass V at temperature T', then enters the heater H, which should not be
an indefinite storehouse or magazine of heat like present types of boilers, but
rather have its fires of gas or coal so governed as to heat the mass V only to some
desired, and for the time being constant maximum T, no heat being stored.
Issuing from H at the temperature T, the mass V then enters the first boiler B,
where it supplies the heat necessary for one stroke of the engine g, being thereby
cooled to T. Thence it passes on through all the boilers in succession, surrendering
beat for one stroke to each, finally leaving the last boiler, B., at some temperature T
which is so regulated as to give any desired "cold interval," I, above the cold
temperature T of engine a, so as to afford a suitable "working interval" between
the hot and cold temperatures of the coldest engine. This working interval may
ordinarily be about 30° C., but may be increased or decreased within wide limits
without affecting the nature of the process.
Finally, the mass V, having surrendered all its heat deemed capable of useful
work, enters the cooler C, where I degrees of heat (IV heat units) are abstracted
from it and rejected, in order to reduce the mass V again to its original tempera-
ture T', at which temperature it again issues from the cooler to repeat its circuit.
The heat thus abstracted and rejected in the cooler is an unavoidable waste to
create the "cold interval" which enables the engine to work at all.
Furthermore, let each of the several engines, instead of working between its
given temperatures in the usual manner of single cylinder engines, so as to give a
diagram like the outer lines of Figure 11, be working so as to give a diagram like
the shaded area only, corresponding more nearly, though still imperfectly, to the
high pressure diagrams of compound engines. That is to say, let the steam be
admitted from the boiler at the pressure corresponding to its effective temperature Ta
and cooled by expansion and work only down to the pressure corresponding to its
condensing temperature T'. This condensing temperature and pressure may be
and ordinarily will be pretty high. It will be seen more clearly later that it is
д

page_text: ordinarily economical to have it so; but whether high or low, we extract from the
steam in this way all the work which is possible between the given temperatures,
which is all we require.
or
For convenience, certair terms that require definition are used herein, and the
above description and diagrams make the following clear. The engine at the
"cold end," e, nearest to the cooler, is hereinafter termed the "cold engine," and
the engine at the "hot end," or nearest to the heater, is termed the "hot engine."
Their several boilers and condensers are correspondingly designated as "cold"
"hot." The interval of temperature within the whole series, T-T', is termed the
"thermal range" in distinction from the "working interval," I to I', of the separate
engines at any point. The boiler circulating passages are termed collectively the
"bot circuit" and spoken of as on the "hot side," while the condenser circulating
passages are correspondingly designated as the "cold circuit" or the "cold side."
Other new terms will be explained as they arise.
Proceeding now to a full description of the theory and methods of practising the
series engine process, a number of the theoretical properties of the process and
engine in the form outlined above require to be explained.
It will be seen that each single engine, in Figures 9 and 10, -eparately
considered, uses its own special heat with perfect efficiency, barring external
radiation and internal conduction, since all the heat it receives is either converted
into work ci passed on to the cold circuit undegraded in temperature except by
the process of expansion, and used over again later without degradation of
temperature in that circuit. No one of the engines voids any heat externally at
any temperature, or degrades any in temperature except by the process of
expansive work, but all the heat voided externally or degraded wastefully is
voided through the cooler, from the circulatory system only and not from the
several engines.
The efficiency of the seues as a whole is measured approximately, and, with a
small correction for external radiation, exactly by the ratio of the hot interval I',
or heat supplied, to the cold interval I, or heat voided without conversion into
I
work, the ratio of heat wasted being and the ratio of economy, or of heat
I'―I.
converted into work, being II-I.
I'
The percentage of economy with which the
engine is working for the time being may therefore be determined at any moment
from thermometric observations only.
It will be seen also that the quantity of heat to be rejected in the cooler is
entirely independent of the number of engines in series, or of the total thermal
range T-T. Whatever the number of engines in series, the rejection for the cold
interval must still be the same, 1, Figure 10, remaining constant, being that
required to give a suitable working interval for the cold engine, which may be
10° to 50° C. For example, we may extend Figure 10 indefinitely to the right by
prolonging the inclined lines and pushing I' further outward and upward without
changing the conditions of the original series as shown.
This working interval once fixed for the cold engine it widens continuously
toward the hot end from the nature of the process, because each "hot increment,'
or change of temperature from one boiler to the next above it, must necessarily
exceed the "cold increment," or change of temperature from one condenser to the
next above it, by the degrees required to supply the heat for work (w, to wg,
Figure 10) to that engine. Toward the hot end, the working interval is thus
materially increased. If the series be working with an efficiency of 50 per cent.
the hot interval is 2 I; if with an efficiency of 40 per cent. the hot interval
is 1.67 I, etc. Thus the cold interval may properly be made narrower than it
otherwise might, especially in a long series, as the original working interval
continuously widens toward the hot end.
If we divide the series into two parts, by a vertical line at any point in

page_text: Figure 10, it will be seen that all the rejection of heat from the system is confined
to the cold side of the line. All the engines on the hot side, taken as a whole as
well as individually, are working absolutely with complete efficiency; that is, if
we cut them off, we lose all their work but we save only the heat which they were
actually converting into work. The general thermal waste of the system, which is
confined to the cooler, remains undiminished. Therefore, if we extend the series
by adding more engines which extend the thermal range, as may be indicated by
mentally prolonging the inclined lines in Figure 10, the heat wasted in the cooler
is not increased, and the heat supplied needs to be increased only by the amount
actually converted into work by these engines. In other words, if we have given
any part of the cold end of a series, even if it be only the cooler itself, every
engine added on the hot side of it which increases the thermal range, as in
Figure 10, demands only so much more heat as it actually converts into work, and
hence works with complete efficiency. This is an important and fundamental fact,
which must be always borne in mind.
It may appear from this as if the economy depended solely or chiefly on the
number of engines in series, but this is true only with important limitation-.
Practically, it is neither necessary nor expedient to use many engines in series ;
rarely more than six to twelve. For any given thermal range T-T', and any
given cold interval I, the theoretical economy of a series cannot be either increased
or diminished by varying the number of engines within the given thermal range.
Thus by doubling the number of engines, as shown by the interpolated dotted
verticals in Figure 10, and also doubling the circulating mass V per stroke, we
shall double the power, but we shall also double the quantity of heat supplied and
voided per stroke, the economy and temperature scale remaining constant, but the
hot and cold increments being halved.
The economy of such a series is also not materially effected by varying the cold
interval if we permit the work W, and hence the maximum temperature T, to
vary correspondingly, as they naturally do. In that case, we simply vary the
vertical scale of Figure 10, barring thermodynamic fractions, and leave our
economy substantially as it was. Within moderate limits the same is true of
changes in the cold interval I only, the maximum temperature T remaining
constant. From the general equation of efficiency, based on the Carnot theorem,
it follows that, the maximum and minimum temperature, T and T', being constant,
there should be always a slight increase in the percentage of economy by
decreasing the cold interval I, since we decrease the quantity of heat which is
voided wastefully at a temperature higher than the minimum T'; and vice versa
for an increase therein. But the value of the negative term which expresses this
loss in the equation of efficiency is relatively small in any case; and hence moderate
variations of the cold interval alone will not materially modify the economy,
though they will largely vary the work W.
On the other hand, to vary the work of the series by increasing or decreasing
the maximum temperature T should by the general theory of Carnot vary the
percentage of economy in almost direct ratio thereto, and it does in fact do so, as
will appear more fully later. If the normal value of the maximum temperature T
be made as high as the materials conveniently permit, which economy requires, it is
not possible to increase the maximum materially; but it may be decreased ad libitum ;
and as a moderate increase or decrease will materially modify the working pressure
and consequent power developed, it is possible, though not expedient, to work with
a constant cold interval and an automatically regulated or hand regulated
maximum temperature. In this case the cold interval I is kept constant by
regulating the speed of circulation, the circulation being checked when I tends to
increase, and accelerated when I falls too low. A better method of regulation in
most cases, however, is to maintain the inaximum temperature T constant for the
time being by any regulative method, and to regulate the work of the engine by
automatically or otherwise varying the cold interval I by varying the speed of
circulation, all as hereafter fully explained. It will be understood that the.

page_text: regulation bere referred to is not that from moment to moment, which is effected
in the usual way by any form of engine governor, but that which is desirable from
day to day, or hour to hour, to adapt the engine to the average load for the time
being. The economy of the engine depends quite largely on selecting the best
cold interval for a given out-put of power. Almost any combination of these is
possible under the theory of the engine, but only a few are expedient, the rest
being relatively wasteful.
The power of the series may be almost instantly destroyed by reversing the
direction of the circulation. The normal speed required for circulation being slow,
it may be very suddenly checked and reversed. After it has moved a few feet
backward, all generation of steam and all condensation ceases, since the thermal
head is so small in the best practice, that a slight backward movement makes the
circulation colder than the steam on the hot side, and hotter than the exhaust on
the cold side. After moving a few feet more, the action of the boilers and
condensers becomes reversed, and hence the cylinders become compressors, the
engine working steadily against a pressure instead of with it. To the end that
this may be so, it is not desirable to drain the condensers too completely of liquid
working substance when it is desired to utilize this possibility. This reversal may
be effected, when a circulating pump is used, by reversing the pump, or by having
a small pump for this special purpose, which may even be a hand pump, since
merely stopping the circulation makes the engine dead in a few strokes..
It is a very important, in fact fundamental, principle of design, to reduce the
"thermal head," or difference of temperature between the heating and the heated
substances, to the lowest attainable limits. In present ordinary practice, this
thermal head runs up to several hundred degrees and cannot be determined exactly,
for the reason that it varies enormously both in different parts of the boiler and
in the same part at different times. It is a leading advantage of the peculiar
method of generating vapor pressure by a circulating Huid, as heretofore described,
that for reasons already explained it reduces this thermal head largely, to say 50°
to 80° C., while at the same time practically eliminating the boiler as a factor in
the bulk and weight of engines. But for this series process it is desirable to
reduce the thermal head further yet, say preferably to 2° to 10° C., for which
reason I prefer to use boilers having from ten to twenty times as much surface per
horse power as is necessary or useful when their steam is to be used in the now
recognized ways: that is to say, I use from twenty to forty sq. ft. per horse power
for engines in series, whereas for mere steam generating purposes, two sq. ft. is
ample, calling for some 40° C. of thermal head only. But as
may obtain with
ease one hundred to one hundred and twenty sq. ft. of heating surface per cubic
foot of boiler, it will be seen that, even after this large increase of surface, the
boilers still remain of insignificant bulk compared with those of present practice,
since they give from three to six horse power per cubic foot, instead of requiring
that many cubic feet per horse power, as do approved present types of boilers.
The objection to a large thermal head in the series process is that, if it exists on
the hot side, it must exist on the cold side also, to about the same extent, and that
the circulating fluid must be cooled wastefully in the cooler through the number
of degrees represented by these two thermal heads, as well as through the
theoretical cold interval which represents the interior interval for work of the
cold engine. In order to maintain in practice the interior working intervals of a
theoretical series working without thermal head, therefore, the hot circulation
must be made hotter and the cold circulation colder by a number of degrees equal
to the thermal head, and this extra heat does absolutely no work except to give
the necessary thermal head to force heat through boiler and condenser surfaces at
the required rate. If the thermal head be large it may materially decrease the
percentage of economy, though the loss from this cause is not so serious as might
appear at first sight. By doubling the cold interval rejection because of the
thermal heads, for example, in a series which would otherwise work with 50 per cent.
economy, we by no means halve the percentage of economy, but only reduce it by

page_text: one-third or to 33 per cent. economy, and the higher the efficiency of the series
otherwise, the less the percentage of waste from given thermal heads.
It is not essential and often not expedient that the circulating fluid should pass
directly from the cold circuit to the heater, but a part or all of the circulating fluid
after it has passed through the cold circuit, and thus been reheated nearly to its
original temperature, may be used as the hot circulation of a new series of
somewhat smaller thermal range before returning it to the beater to be reheated,
and this may be done a number of times until the entire thermal interval is
exhausted. This is termed the "multiple series process.
"
Figure 12 is a diagram showing the circulating fluid thus u-ed with two series S,
S', and Figure 13 a temperature diagram showing the use in this manner of
substantially the entire thermal ange. In such multiple series, separate coolers
are required for the different series, which may work with the same or different
cold intervals, but a single heater serves for all the series. The advantage thus
secured is that the same heat supply is used over and over, thus obtaining much
more power from a single heater, and that the circulating fluid when it finally
enters the heater is very much colder, and so can cool the gases of combustion
down to a very much lower point before discharge, and the same heater may thus
be made to furnish correspondingly more power, either in emergencies only or
regularly.
The disadvantage of this multiple series process is that the mean efficiency of heat
conversion is not increased but decreased, each succeeding series of engines being
of lower efficiency than the one above it, because of smaller thermal range.
It is,
therefore, better, when it can be done, to utilize the entire heat supply generated
by the heater in working a single series as may always be done by making the air
supply and gases of combustion a part of the circulating fluid, as hereafter
described, but when special conditions make this inexpedient or impossible, the use
of such multiple series may often be highly economical in practice.
Nor is it necessary to use additional mechanisms to obtain this multiplication of
power at the expense of economy provided only that we may gain the power by
increased piston speed or mainly so. In that case, we may carry out this multiple
series principle with a single series of engines by the sub-circuit modification as
follows, and as shown in diagram in Figure 14:—
After the circulating fluid has made its first circuit, instead of passing it to the
heater at the temperature and point T', we may introduce it again into the hot
circuit at or near the point where the hot circulation attains this temperature, and
thus send the mass V around on a second shorter circuit. Similarly when this
mass has completed its second circuit, we may either pass it to the heater to
be reheated, or again re-enter it into the hot circuit at the point of corresponding
temperature, and send it around on still a second sub-circuit, and so on through
successive temperatures T'm T₁ until it has attained some temperature T', which
is too cold to warraut another circuit, when finally it is passed to the heater. In
this manner both the speed of circulation and the power developed are multiplied
and caused to vary about as the number of arrows shown along the hot circuit.
The normal speed of circulation is so slow that this increase, although it is four
fold or more at the cold end, involves no inconvenience or special appliances, while
the power developed is multiplied largely, the mass of circulating fluid being cooled
several times, though reheated only once, so that the tax upon the heater is not
sensibly increased, and the moderate sacrifice of economy, at least in emergencies,
may be no consideration.
The otherwise great field for the application of this principle of multiple series
is limited by the fact that all heat produced by combustion is initially high
temperature heat, and if careful arrangements are made to collect and utilize this
heat at a high temperature, as by allowing most of it to radiate directly from the
fires to the circulating pipes, there need be no sensible loss in the fact that the
substances to be heated are themselves received at a pretty high temperature; but
as such arrangements rarely are perfect, and, as the same advantage of using the

page_text: same heat over and over still remains, there is a considerable field for the application
of this principle.
The power of a series may be instantaneously doubled or tripled at the expense
of economy, by providing a by-pass for the circulating fluid on the cold side to
carry it past one or more of the condensers and substituting in lieu thereof a
cold injection of the ordinary kind through the tubes of those condensers which
rejects and wastes the heat. In this way, although the temperature change in
each condenser only 30° to 40° C. all the higher engines may work through a
very great range with corresponding increase in the power developed by them,
though with a change of only 30° C. more or less, in the condensing temperatures.
To take advantage of this possibility to the fullest extent and for any length of
time, it will ordinarily be necessary to provide for supplemental heaters, as tripling
the power in this way might multiply the coal consumption ten fold or more; but
in emergencies, when economy is no object, the possibility of this operation is of
great value and easily provided for. It tends directly to economy, especially in
war vessels, by making considerably smaller engines than would otherwise be used
adequate for all emergencies.
In broad distinction from ordinary types of engines, which must work at a nearly
constant and fall power or fall off heavily in economy, a series engine is of no
particular horse-power and works or may work with its highest economy when
producing but little power. This last results from the fact that, as the governor
will then cut off earlier, less steam will be used, and hence the quantity required
will be produced from the large heating surfaces with a proportionately reduced
thermal head, which at times may be hardly more than nominal. But we may increase
such a nominal thermal head five to ten fold, with an approximately proportional
increase of steam supply and horse-power and still not increase the thermal head
to a point which seriously sacrifices economy, while by temporarily disregarding
economy we may increase it twelve to twenty fold; for naval engines and many
others this peculiar property is deemed of great importance.
The general theory of the series process proper and resulting engine having been
explained, we will now consider more fully the general methods of carrying the
invention into practice.
The separate engines or cylinders which are the immediate sources of power
may be of any suitable type, no change being required from ordinary methods of
construction so far as these features are concerned. Two or more cylinders or
their equivalents must be used together to convert them as a whole into the new
type of engine, but these primary cylinders or engines may each individually be of
any known or unknown type obtaining power from the expansion and consequent
cooling of a hot working substance, whether steam engines, hot air engines, gas
engines, or any other kind of expansion heat engines, so long as they conform to
certain simple conditions to be enumerated, and fitting them for this special use.
The separate engines may either be all alike or all different in type or size or both.
Practically, for mechanical reasons, the engines of any given series should ordinarily
resemble each other, but functionally this is indifferent. It will probably be found
preferable as a rule that the separate engines or cylinders should be a number
of ordinary late cut-off single cylinder steam engines of simple type, all of one
size and working at pretty high and nearly constant pressures, but between slightly
different temperatures, which decrease toward the cold end. All these conditions
may be varied within wide limits, however, and it is possible that in some cases the
best practice will be that no two engines will be of the same type or size.
also possible that some development of steain turbines or rotary engines may prove
more suitable for this process than any other form of eugine. The process may be
used with pressure generators of many different forms and some of the possible
advantages secured, but it is practically necessary that the pressure generators
should be of the special construction and functional action previously described in
connection with the general process of pressure generation.
It is
The pressure generators, therefore, will preferably be so arranged that the

page_text: circulating fluid is applied first to the hotter parts and then to the colder parts of
the working substance by passing it downward through circuitous passages forming
uniformly distributed and closely spaced heating surfaces, preferably filling both
steam and water space, the heating and heated substance being carried in opposing
currents past each other. By thus introducing differential temperatures within the
chamber, we reduce largely the mean thermal head, as previously described in
connection with the step series process, which reduction of thermal heads is of great
importance in the process now being described. As in the step-series process and
as above stated, it is of importance that the heat transmitting surfaces be thin, thus
not only securing the advantage of providing a large amount of heating sui lace in
small space, but aiding directly towards obtaining the very small thermal heads
desired.
As stated above in connection with the general process, I have found that the
pressure generator will ordinarily give the best results when two-thirds to four-fifths
full of liquid, and it is better to have a considerable area of heating surface, perhaps
ten to fifteen per cent. of the total, devoted to superheating uses alone. It follows,
therefore, that the best pressure generator for use in this series engine process will
consist of a mass of thin heating surfaces filling steam space and water space alike
without any distinction between them, and with no greater total bulk than is needed
to ensure enough heating surface, with the circulating fluid or heating substance
entering hot at the top and working its way downward to the bottom, and with the
working substance, or substance to be heated, entering cold at the bottom and
leaving hot at the top without circulation.
The same principles are preferably applied in the construction of the condensers,
the exhaust from the engines entering at the top and passing out at the bottom
and the cooled circulating fluid entering at the bottom and passing out at the top.
This is so strictly true that in all their details, the condensers and pressure
grenerators are interchangeable duplicates in my present practice, and coolers and
transmitters, if used at all, are also interchangeable duplicates of the pressure
generators and condensers.
It is not absolutely essential that all the pressure generators should be thermally
dissociated and supplied with beat from the circulating fluid. The hot boiler
might, if desired, be exposed to the direct heat of a fire which also heats the
circulating fluid, but to a lower temperature than that required for the hot boiler.
Special circumstances may render this expedient occasionally, but ordinarily it
would be disadvantageous.
The working substances may be used either in closed or open cycle, but it
will usually be found expedient to use them in closed cycle, especially as the
working substance will rarely be water, but ordinarily some more or less costly or
noxious substance, like the petroleum distillates, vaporizing at higher or lower
temperatures than water; so that economy of supply is more important than
with water.
The circulating fluid may be a liquid, or it may be solid or gaseous in part or
hole, and its sole function as a part of this process is to convey heat to the working
substances in the successive pressure generators and abstract heat from the exhaust in
the successive condensers, and it may consist either of one or of several different heat
conveying substances circulated either as a common mass, or, as is often expedient,
for practical reasons, in two or more distinct sets of passageways, but in either case
it is spoken of collectively as the circulating fluid.
Some part of the circulating fluid, if not all, will usually be employed in closed
cycle, being alternately heated to a desired or convenient point, ordinarily not
exceeding 300° to 425° C., passed around the circuit as described, and directly or
indirectly returned to the heater to be reheated. In certain cases, however, it is
inexpedient to use over and over a single mass of circulating fluid. For instance,
an external mass of air or water may often be drawn upon with advantage for the
circulating fluid, and used in open cycle, a fresh mass of this existing supply being
continuously received at the cold end of the cold circuit and passed through the
1:

page_text: cold circuit, heater and hot circuit to the cold end of the latter, where it is
discharged to waste hotter than received or used for any purpose desired such as
heating ships or buildings, and the temperature at which it is discharged will
ordinarily adapt it to such use. In all cases, moreover, in which fire is used for
heat, a continuous supply of fresh air must be taken into the heater to support
combustion, and the gas thus used may most advantageously be made a part of the
circulating fluid in the manner described.
Suitable circulating fluids in the order of their usual merit are water, air or other
gas under atmospheric or higher pressures, and paraffine or other oils, but it is not
necessary, and as a rule not expedient that the circulating Buid shall consist wholly
of either air or a liquid. A mixed circulation consisting in part of each is in general
recommended. The advantages to be had from each substance may thus be in large
measure secured, and the disadvantage of each eliminated. To this end, the air
circulation should be made sufficient in volume only to support combustion properly.
It is not necessary to calculate very closely, since the theory of the engine warrants
and requires that the products of combustion shall be lowered in temperature even
more than they are likely to be by any probable air excess before they are permitted
to enter the pressure generators.
Because of the lower heat efficiency of the passages carrying this air, however,
as few as possible of them should be devoted to the air circulation in excess of what
is required to supply air for combustion. Ordinarily some ten per cent. of the
heating surfaces at most may suffice for this use, as the speed of the air through
them may be high. All the remainder of the circulating passage-ways may then be
devoted to liquid closed cycle circulation and therefore, as a net result, we obtain
from nine-tenths, more or less, of our heating surface the highest transmitting
efficiency, while still retaining that complete combustion economy which
obtainable only by using air in the circulating fluid.
IS
Nor is it necessary that any of the interior heating surface of the pressure
generators should be given up to this air circulation, as a nearly identical though
less perfect thermal action may be obtained by passing the air circulation through
passages around the shell of the pressure generators. The most serious objection
to doing so is that this sacrifices part of the advantage of a double circulation,
as follows:
It is not necessary or expedient to have the two circulations at exactly the same
temperature. It is a practical convenience to have the combustion products at a
higher temperature than the liquid circulation, and by passing this hotter circulation
through the tops of the boilers only, this gives an easy way of further superheating
all steam just before it is used, as shown later, as also to jacket the engine cylinders
with a higher temperature than is otherwise possible.
When part or all of the circulation is air used in open cycle as a supporter of
combustion as well as a circulating fluid, and when the fuel used is gaseous
or liquid, or solid particles in the form of dust, a further improvement may be
effected by passing the fuel as well as the air through the cold circuit on its way to
the heater, the fuel being already mixed with the air, or uniting with the latter at
the heater. In this way the two may be heated to quite a high temperature before
combustion and the thermal balance between the hot and cold circuit is better
preserved, since the same fuel also goes through the hot circuit in the form of gase
of combustion. In theory this should be done with any fuel, but with solid fuel it
is impracticable under ordinary conditions.
An important and conspicuous advantage of the series engine process in all its
forms is that it readily admits of working through a very wide range of temperature,
not only without disadvantage, but with an actual advantage, that is to say, working
through 200° C., instead of only 100° C. does not even require that the bulk of the
engine as measured in cylinder volumes shall be doubled, whereas to increase the
range of present types of engines even one-half this amount requires, even in
theory, that their bulk shall be increased eight fold, and practically it is not
possible to do this at all. The reason for the rapid and prohibitory increase in bulk

page_text: in present practice as the thermal range is increased, lies simply in the fact that
with high ratios of expansion and wide thermal ranges, the terminal pressures
become so low that enormous cylin ler volu nes and piston areas are required to get
a very little more work. Therefore, the practical advantage of wide thermal ranges
in existing types of engines are exhausted long before the theoretical limit is
reached, even if we assume that the full theoretical gain from expansion can be
realized in practice; but when we consider also the heavy internal losses from
theoretical efficiency, which increase mach faster than the ratio of expansion, the
practical limit is reached much sooner.
But in the new series engine process the mean effective pressures and ratios of
expansion are, or may be made, quite independent of the number of separate
cylinders or engines and of the total thermal range, by a proper choice of working
substance, of which there is an indefinite supply. It follows that we may increase
our thermal range at either end by adding more engines without any increase in
engine bulk per unit of work, and hence without mechanical disadvantage. As we
have already seen, the ratio of the hot interval to the cold interval, an l hence the
mean working interval of the engines in proportion to the cold interval rejection, is
greater, the longer the series and total range. But the work done by each engine
for a given heat supply varies, within our required limits, almost exactly with its
working interval. Therefore, we can either decrease our coll interval rejections as
we lengthen our series and thermal range, or keep it unchanged and increase our
mean working interval, with the final result that the total cylinder volume for the
highest economy increases somewhat less rapidly than the thermal range, instead of
more rapidly than the square of that range, as do the present type of engines when
the range is at all extended.
Now, there is a point in the design of engines, at which, on a balance of all
considerations of first cost, durability, steam economy, etc. either increasing or
decreasing the size of a cylinder for given unit pressures gives a less economical
engine. The point is not well defined, for the reason that there is a considerable
ange on each side of it within which the exact size of the cylinder matters little.
It is only very large or very small cylinders which are distinctly uneconomical.
These limits of reasonable economy should not be exceeded; but within these limits
it is or should be a fundamental principle of design under this process that many
small engines (ie cylinders) working through a wide thermal range collectively,
but through a small working interval individually, are vastly more economical than
a few large engines or cylinders working through a smaller range; and not only
will they generate a given power with less coal, but they will, within the limits
defined, generate it with less percentage of loss by friction, and with less total
bulk, weight and cost.
It follows from these facts that the desired thermal range is likely to be several
hundred degrees in all important and well designed series, which makes it more than
possible that even paraffine oil or other like liquid will not permit of using all
desired temperatures in the circulating fluid without physical change in it.
If 80,
it will then be necessary to use two or more circulating liquids, boiling or freezing
at quite different temperatures, in order to cover the range desired. This may be
effected without any change of theoretical conditions, and with but little practical
inconvenience by using one or more "transmitters" having the function of heating
up the colder circulating fluid so as to fit it to pass from the cold to the hot circuit,
by the act of cooling down the hot circulating fluid, so as to fit it to pass from
the hot to the cold circuit. The heat is merely transferred from one circulating
fluid to the other, and as the transfer is made only for mechanical or chemical
reasons, and has no thermodynamic significance, the two circulating fluids must
necessarily have the same mass V per stroke, and theoretically it is only necessary to
pass the two currents by each other in opposite directions and in sufficiently intimate
contact to have each assume the temperature of the other on leaving the transmitter,
which may be approached practically within a few degrees. In mechanical con-
struction under this process, boilers, condensers, coolers and transmitters are

page_text: preferably interchangeable duplicates of each other, all having the common
function of transmitting heat from one fluid to another through metallic walls with
a small, the least possible, thermal head to effect the transfer. This broad principle
may of course he occasionally varied from in practice, but ordinarily to no greater
extent than to vary the quantity of heating surface.
As above stated, the separate engines of the series will usually be worked in
closed cycle, or with boiler and condenser, so as to enable a small and constant
mass of working fluid to be used over and over, enabling the fluid to be used
regardless of cost, scarcity or noxiousness when free, the circulating fluid being
applied to condense the working substances and receive the heat rejected there-
from. Certain important advantages, however, may frequently be realized by
omitting condensers from certain engines of the series, when a part or all of the
circulating fluid is air or water used in open cycle and the working substance of any
In such
particular engine or engines is any abundant and harmless substance.
case that particular engine or engines may be worked high pressure in the usual
way, a new mass of hot working substance being received at each stroke, expanded
as far as convenient. and rejected in this slightly cooled state into the open cycle
circulation, where all heat still remaining in it above the minimum is utilized, so
that the heat of vaporization, as well as the sensible heat, is utilized in the series.
The application of this principle is subject to the limitation hereafter explained,
that no large part of the circulating fluid can be a condensable vapor, but without
exceeding this limitation certain important advantages may be secured, among
which are the following: Condensers for such engines may be dispensed with;
the thermal range of the hotter engines of the series is increased; there is no
loss due to the condensing back pressure of the condensers dispensed with; the
average temperature of the circulation is decreased, so that the voiding air
temperatures of the heater may be higher, and consequently the heating surface
of the heater smaller and its bulk less; the air circulation is enriched and may
consist in part of steam, so that it will transmit more heat for given volume and
surface and the bulk of the boilers be less; by giving this exhaust jet the right
direction an induced current may be set up sufficient to maintain the necessary
open circuit air circulation or to give the desired draught for the fires if there be
no such circulation, thus dispensing with a suction or other fan and simplifying the
mechanism.
Moreover, these non-condensing engines may be wholly external to and separate
from the series and yet the thermal conditions will permit of using their steam
with as great efficiency as if so many engines had been added to the series. Thus
one or more engines and boilers of the usual or any suitable type may be placed
in any convenient position relatively to the series engine, and the air supply for
these engines, and preferably the water supply also, be carried through the cold
circuit, the products of combustion being voided as is now usual, resulting, of
If the steam from
course, in the usual boiler loss of 25 per cent., more or less.
these boilers be worked non-condensing through their separate engines and after
exhaust mixed with the hot circulation of the series engine as it leaves the heater,
the result will be that all the heat in that steam above the minimum temperature
for the time being, which always in practice will be well below 100° C., is surrendered
in the hot circuit before its discharge therefrom liquified, saving the heater of
the series engine that amount. The thermal balance of the series engines in such
case, is not disturbed and yet small separate engines, working exactly as they do
now, are enabled by conditions external to them to work with practically 100 per cent.
efficiency of the heat in their steam, since every heat unit in them which is not
converted into work saves the series heater a corresponding amount. Even the
comparatively low temperature of the exhaust steam is not a theoretical loss.
is a practical convenience to have this low temperature heat to mix with the high
temperature heat in the gases of combustion from the heater, in order that the
two together may not exceed the required temperature when they enter the hot
circulation; and as we do not avail ourselves of the interval between the temperature
It

page_text: of combustion and the working maximum temperature T of the series, no theoretical
loss results. The separate engines are assumed to have separate boilers and fire
boxes as the more extreme case. When they simply borrow a part of the
circulating fluid or steam from some series boiler, they become thermally a part
of the series, though dissociated mechanically, and it is still easier to make them
work with the full economy of the main engine.
This element of the complete series engine process has the great practical
advantage for marine use, that by it all or nearly all the numerous small engines
required about ship may be worked with high economy while left mechanically
just as they are now, or even with still less attention to their separate econo.ny.
But in addition, it is likely to be desirable to have at least one non-condensing
engine in series in order to secure the other advantages stated above under that
head.
A general principle limiting the application of such dissociated engines may
here be stated without detailing reasons, which would occupy much space for a
comparatively unimportant point. Heat from an outside source cannot be thrust
into the hot side only of the circulation with much resulting economy.
We may
not always lose, but we often shall, and in no case can we gain by so doing more
than a small percentage, the lumit being about 10 per cent. conversion of the heat
supplied. The thermal balance of the circulating system must be preserved to
realize fully the economies last stated i.e. the external source of heat must be in
effect interpolated into the circulation between the cold side and the hot side, and
affect both; becoming then in effect merely an annex to the heater.
A further general principle limiting the use of dissociated engines is that, while
generally, as above stated, the material of the circulating fluid is functionally
indifferent, any large percentage of a vapor which condenses in the circulation, is
undesirable in the series. This results from the fact that, from the very nature of
the process, the circulation should change in temperature as it receives or surrenders
heat, and the theory of the process assumes it will. If it did not, the engines in
series could not work between successively decreasing temperature. It is possible
for them to do so to a sufficient extent, even though considerable vapor be
condensed in the circulation, but any large amount is to be avoided.
To this general rule, however, there is one important exception. If we make
the circulating fluid a mere mechanical mixture of substances boiling at different
temperatures, selecting these substances in such manner that each may tend to
condense in some one boiler, the least volatile at the hot end and the most volatile
at the cold end, then entirely different conditions, which in some respects are highly
advantageous, will prevail. In the first place, we no longer need an expansion
tank, since a large part of our circulation is in the gaseous state. Secondly, we
gain that abnormal intensity of heat transfer which exists only when a liquid is
changing into vapor or vice versa. Thirdly, a vapor circulates so much more rapidly
than steam, and carries so much more heat per pound, that no larger passages are
essential, while the circulation will for the most part propel itself. Crude
petroleum stripped of its most volatile and least volatile constituents, furnishes a
natural circulating fluid of this nature, as it does a series of working substances;
and, in general, any series of suitable working substances will by merely mixing
them together and introducing the mixture into the circulating passages, furnish a
good circulating fluid also, provided only that their physical properties as liquids
are such that they readily mix, nor is even that absolutely essential.
The regulative features are in general the same as already described fully in-
connection with the general process and need be referred to but briefly.
To obtain the best results, whether the circulating fluid be a liquid or a gas, or
partly both, it should include the regulation of the maximum and minimum
temperatures of the circulating fluid in the hot circuit; that is, the regulation of
the temperature of the circulating fluid as it enters the first pressure generator of
the series and as it passes from the last pressure generator. On the cold side no
Regulation is necessary, because the very function of the circulating fluid on the

page_text: cold side is to absorb all the heat delivered to it, which latter is always a certain
function of the heat delivered from the hot side.
The regulation of the maximum temperature of the circulating fluid is very
important when the fluid is heated by the direct action of fire. When a circulating
fluid is drawn from a supply already regulated in temperature or the methods of
heating be such as to assure the desired temperature of the circulating fluid, of
course this feature may be omitted. The methods of securing this regulation have
already been fully described. The best method of regulating the minimum
temperature of the circulating fluid is by a thermostat located at the cold end of
the hot circuit and regulating the speed of circulation, as previously described.
It may be found desirable, also, to regulate the volume of the circulating fluid,
and the quantity of the working substances in the different pressure generators,
especially with large engines. Regulation of the degree of pressure that can exist
in the different pressure generators will usually not be of importance on account of
the small thermal heads employed, but other provision for such regulation may be
needful occasionally. For all these regulations any suitable means, such as those
previously described, may be used.
So far, we have considered engines in series only. We now come to certain
desirable additions to the basic series process, effected by additional engines.
It will be understood that the cold interval necessary to give the working interval
for the last engine may be secured by any suitable cooler and the heat may either
be wasted by such cooler, or a cooler of such form as to utilize the heat may be
used. Thus, heat may be abstracted from the circulating fluid, and the latter
cooled, by using the circulating fluid for any sort of external heating, such as
heating ships or buildings, for which the temperature of the circulating fluid after
leaving the last pressure generator will usually be well suited, or for any other
purpose which involves the abstraction of heat, so as to utilize the heat that might
otherwise be wasted to secure the necessary cold interval.
An important economy may be effected by utilizing the heat which must be
rejected by the cooler in "Cold Interval Engines added for this purpose, and
such use forms an important addition to the process and apparatus. This result is
attained by adding one or more cold interval engines t, u, v, as shown in diagram in
Figure 15, which mechanically may, and should appear as a part of the series, but
functionally are outside of it, each having its own independent condenser, Cr, Cu, Cv,
from which the heat voided by it is rejected to waste and not returned to the
circulation. Thus, the rejection of heat required for the cold interval is in part
effected by converting it into work externally, and in part only by wasteful
rejection.
The mechanical arrangement necessary to add these cold interval engines is clear
from the diagram, the hot circulation being carried through their boilers in the
same manner as through the boilers of the series engines, the cooler at the end of
the series being omitted, and the cold circulation being carried through or past
their condensers without permitting any rise of temperature therein above T',
Figure 10. This last may be effected either by carrying the circulation past their
condensers without entering them at all, as shown in Figure 7, or by carrying the
circulation through the cold interval condensers in the same manner as in the
series condensers, but with provisions for cooling it down again after passing
through each cold interval condenser by voiding the heat it has received in that
condenser.
If the circulating fluid, in addition to being a heat carrier, be a vapor or gas in
a state of compression, so that it may itself act as a working substance and do
work by expansion, as I make it in certain special applications of this process, this
sanie work will or may cool the circulating fluid sufficiently, and it then becomes
uunecessary to have any cold interval boilers or any separate cooler or cooling
process to accomplish their functional purpose. In the special applications referred
to, this becomes of much importance. The cooler and cold interval engine or
engines then become one. The circulating fluid may, if desired, be merely

page_text: permitted to expand at the cold end in order to create the cold interval. In that
case the cooler becomes a mere pipe and release valve, and there is a waste of
possible work precisely analogous to that from the omission of cold interval engines.
But if for the pipe and valve we substitute a working engine in which the
circulating fluid expands and is thus cooled, useful work is done in this process of
cooling, and thus this working cylinder in which the cooling is done becomes at
once a cooler and a complete cold interval engine, as stated.
Considering the properties of the process outlined in Figures 15 and 16, the latter
showing the temperature conditions when engines in series and cold interval engine>
are worked together as one mechanism, as above described, we find that a series of
whatever thermal length thus provided with cold interval engines constitutes
theoretically a Reversible Engine according to the well-known generalization of
Carnot. That is to say, if the mechanism be considered as a whole, it receives all
its heat at the maximum temperature T, degrades none of this heat in temperature
except by the process of expansive work, and voids none of it until it has been
thus reduced in temperature by expansion only to the lowest minimum for the time
being, T', at which a cold body can be found to void the heat into.
Carnot demonstrated that an engine working under these conditions did all the
work that was possible for any expansion heat engine to do between the given
maximum and minimum temperatures, for the reason that if power was applied to
the piston in the same measure that it was before taken from it, heat would be
supplied to the "hot body" in the same measure that it was before taken from it.
In making this demonstration for the ideal case of a perfect heat engine, Carnot
was obliged to assume (1) for his hot body infinite heat supplying or heat absorbing
capacity at the maximum temperature T; (2) for his cold body infinite heat
absorbing or beat supplying capacity at the minimum temperature T'; (3) infinite
conductivity in the liquids or gases and in the transmitting surfaces; (4) absolute
non-conductivity in the other surfaces in contact with the working substances.
These assumptions we also are obliged to make for the theoretical case of
reversibility, but the difference between the Carnot generalization and the complete
process as so far described is that the Carnot generalization is widely different
from practical conditions even within the narrow range of 80° to 110° C., to which
alone it is applied in practice, and beyond that range becomes a pure abstraction;
whereas engines as actually constructed under the process herein described, bear
or may bear so close a relation to the theoretical case as to be nearly identical
therewith, not only within the narrow thermal ranges now customary, but also an
in as great degree for the utmost extremes of range between the highest possible
temperatures which the materials will stand and the lowest temperatures at which
an engine can work and a cold body be found for voiding the rejected heat into.
Instead of passing the circulating fluid from the cold circuit directly to the
heater, wherein change of temperature occurs without work, it is possible to increase
the efficiency and economy of the process still further by the use of "Hot Interval
Engines," working between a constant maximum temperature and an increasing
minimum, which increases because of the gradual heating up of the cold circulation
to fit it for the hot circuit. In other words, in place of heating up the circulation
by the direct application of fire through the heater placed at the end of the series,
the otherwise rejected and lost heat of certain additional engines may be used to
heat the circulation, all of the heat of the heater being preferably passed through
these engines before being delivered to the circulating fluid.
Figure 17, disregarding the engine Z, to be described later, shows in diagrain
two such engines, x, y, added to the series and two cold interval engines, the
heater being shown as extended alongside of these engines. Considering the
properties of the process indicated in Figure 17, and in temperature diagram in
Figure 18, still disregarding the engine Z, that is, the hot interval engines in
combination with the series engines and cold interval engines, it may be seen that,
as these hot interval engines work absolutely with full efficiency, neither wasting

page_text: or degrading any heat except as it must be degraded to heat the circulation, they
are highly economical, and by their addition we attain the paradoxical result of
gaining from the engine theoretically, and practically also, barring a percentage of
loss, a larger amount of work between the maximum and minimum temperaturcs
than the Carnot limit of maximum efficiency makes possible for a single engine
between two given temperatures. We can do this because we are in effect
working two engines between the same temperatures instead of one, one of which
engines has the function of heating up the hot body, and the other of taking beat
from it, and it is of course possible to get more work from a given supply of
heat by passing it successively through two engines than through only one.
Moreover, just as we have seen that the series and cold interval engines are
reversible, so the hot interval engines a, u, may also be shown to be reversible,
considered as a separate engine, and hence the entire combination of series
engines and cold and hot interval engines must be reversible, as it may readily be
shown to be.
As a substitute for or preferably as an addition to this method of extending
the process at the hot end without increasing the maximum temperature T, it is
possible, by further extending the process to include certain gas or other "Heating
Engines" working between high temperatures exclusively to obtain still more work
which is done exclusively above the maximum temperature T, and which in that
case may be done with full efficiency of heat conversion in connection with the
series, so that under favorable conditions it may be highly economical to do so.
We may do this as follows:
Between the temperature of combustion, say 1650° C. and probable values of T,
say 300° C., more or less, there is a wide thermal interval which so far has been
bridged only by the gas engine. The entire interval seems unsuited to the
working of steam engines because of the high temperatures. Because of the
enormous thermal range through which they work, however, the conversion
percentage of the best gas engine is considerably higher than has yet been achieved
or appears achievable with the steam engine, though in proportion to its range it
is far less efficient. In round numbers about 50 per cent. of its heat
the cooling jacket, about 30 per cent. in the exhaust gases and about 20 per cent.
converted into work, under favorable conditions.
rejected in
As the thermal range of the gas engine ends considerably above the temperature
where that of the steam engines begins, there is in theory nothing to prevent the
use of its exhaust heat to run any steam engine, but in practice, owing to the way
in which the waste heat of a gas engine is discharged, and especially the way in
which heat is now supplied to steam engines, this theoretical possibility has had
no practical value, nor any promise of any. The circulatory system of the process
herein described, however, makes it possible to overcome both of these difficulties
to a large extent, at least, and thus to expand the process to cover a further
economy. Figure 17 illustrates clearly the method of doing so, and Figure 18
shows the temperature conditions, with a single heating engine.
In Figures 17 and 18, let Z be a gas engine which also serves as a heater for
the series, the refuse heat from the gas engine being used in place of a fire to heat
up the circulating fluid. Let the series circulation be a double one, in part gaseous,
in part liquid. Then the liquid circulation, which for economy's sake, must be as
large as possible relatively to the air, may be passed around the gas engine jackets
in place of water to absorb the portion of heat usually carried off through the
jackets, which we have seen to be the larger part of the whole.
The gaseous circulation of the series will consist of both air and gas which will
be mixed in, or before reaching, the gas engine and exploded therein so as to give
work and heat, instead of being merely burned in a heater. The waste gases
after expansion will then be turned into the hot air circulation, with or without
some further surrender of heat to the liquid circulation before entering the
circulation, and discharged only after being cooled down in the series circulation

page_text: to a low temperature; or the heat in the gaseous products of combustion may be
all imparted to the liquid circulation, as nearly as may be, and the gases then
discharged to waste.
These heating engines also might be included under the general term hot
interval engines, but to distinguish between the two distinct kinds of such engines,
the kind first described, working below T are alone termed hot interval engines.
and the ones working above T, which apparently must be gas engines if used at
all, are termed heating engines. Any type of engine which will work within the
given thermal range may be used as a heating engine instead of gas engines,
whether now known or yet to be invented, but the thermal peculiarities of the gas
engine process seem to fit it peculiarly well for this special use, with possible minor
modifications, especially such as will permit a somewhat higher temperature in the
jacket circulation.
It may appear from the preceding description that, although there may be gain
in using either hot-interval engines or heating engines separately, there can be no
gain in using both on the same engine; nor would there be if the gas engine were
as capable as the steam engine of gaining a proportionate increase of power from
a slight increase of thermal range. But as a matter of fact, the gas engine is not
capable of doing this. If we conceive a series, as shown in Figures 17 and 18,
provided with both hot interval engines, x, y, and heating engine Z, the latter
would do little if any more work if its range was extended down through the
working range of x, y. On the other hand, by cutting its range short at T, and
adding steam engines below that, the latter will do a great deal of work within
their comparatively narrow range, converting into work possibly 10 per cent. of the
heat which passes through them within a mean range of 33-3° C., whereas the gas
engine will only do twice as much with forty times as great a range.
Summarizing the approximate limits of efficiency for the complete process as so
far described, the heating engines may convert 20 per cent. of the heat generated
within them, and reject 80 per cent.
The hot interval engines may possibly convert
10 per cent. of this 80 per cent. into work, making 28 per cent. of the heat supply
in all which is convertible into work before it reaches the "hot body" of the main
series engines. A series of moderate length may convert into work half of its
proper heat supply, or 36 per cent. of the original supply, rejecting the other
36 per cent. into cold interval engines. These latter may convert into work
7 to 8 per cent. of what reaches thein, or say 24 per cent. of the original supply,
leaving 33 per cent. of the heat only to be rejected at the minimum T', all the rest
having been converted into work. These figures take no account of frictional
or radiation losses, which are likely to be far less than in present practice, however,
but otherwise should in the aggregate be easily attainable, and after more
experience in working at high and low temperatures has been gained should
be easily exceeded, barring the practical losses referred to. By extending the
thermal range of the series engine as far as possible, no reason is perceived why
the above may not be greatly exceeded in ordinary good practice, and carried to
75 or 80 per cent.
The question of back pressure as a separate issue does not arise in the theory or
practice of the series or interval work. There is always back pressure under the
general theory of the engine since it never seeks to condense to the zero of pressure;
but the effect of any difference which may exist between the theoretical and actual
back pressure is already fully allowed for and included in the effect of the thermal
head heretofore discussed. The condensing conditions of the engine are quite
different from those of ordinary practice, in which the aim always is to condense as
nearly as possible to the zero of pressure. Under the general theory of this process,
the aim is always (1) to work with high unit pressures in all the cylinders in order
to avoid unnecessary cylinder volume, and (2) to work through a moderate working
interval only in order to avoid too great a cold interval rejection in proportion to
the total thermal range, T-T'. A typical case may be to expand in each engine
of a series from 12 down to 5 atmospheres, which for an engine using water as
F

page_text: working substance, means working between 188.5° and 152-3° C. or through a
working interval of 36.2° C. The hotter and colder engines should work between
about the same pressures, though between different temperatures. Therefore, there
will be a constant pressure of about five atmospheres in all the condensers, and as
the engine is exhausting from one end of the cylinder or the other nearly all the
time, a nearly constant inflow of steam at five atmospheres will keep the condensers
at work at a nearly uniform rate maintaining that pressure. As the condenser is
a mere duplicate of the boiler yet has less heat to receive by the percentage of single
engine work, it should work with a slightly less thermal head than the boiler, and
maintain the greater pressure due to that thermal head almost constantly.
Therefore, in determining the theoretical loss from that thermal head, as we have
done, we determine also the full amount of all loss from back pressure.
There is no direct thermal loss from clearance, however great, in the series or
hot interval engines, though there is a greatly reduced and ordinarily trivial indirect
loss. In the cold interval engines, clearance causes the same percentage of loss as
in any other engine, in both of which alike the loss results from the fact that the
clearance steam only does a part of the work that it otherwise would, and is then
discharged to waste.
In all of the engines in series, on the contrary, from the hottest to the coldest, as
also in the hot interval engines, the clearance steam, like any other steam, is
admitted at the maximum temperature for that engine, is cooled by expansive work,
and the heat left in it is transferred without further degradation of temperature to
the general circulation, in which it can suffer further degradation only by being
again transferred to some colder engine where it again expands to do work, and so
on down until the heat passes out of series at the temperature T', Figure 19, etc.,
where clearance waste begins. Until then, every condition of the Carnot
generalization is complied with by the clearance steam, as much as any other
steam. Therefore, there can be no direct loss. But indirectly, there is a minor
loss governed by complex laws which does not require explanation here. In this
indirect way, a clearance loss of ten per cent. in the individual engines results in a
net loss of two to three per cent. in the series as a whole.
Neither my series engines, nor my interval engines enjoy any direct advantage
over existing types in respect to the heat which passes through the cylinders
without doing work because of internal radiation, granting the wetness or super-
heating of the steam to be the same in each case. It is expected to secure a
material advantage in this respect indirectly because of the difference in the boilers ;
but so far as the cylinders themselves are concerned, whatever percentage of heat
radiates back into the exhaust is absolutely lost, throughout the entire working
range of the complete engine, as much so as in any other engine. There will be an
apparent but not real economy in this respect, just as there is an apparent but not
real economy in compound as compared with simple engines of the same thermal
range per cylinder. The more work is obtained from the useful quantity of heat
the less will be the percentage of loss per horse power from a constant percentage
of heat loss. In this way compound engines appear to enjoy an advantage over
simple engines of the same thermal range per cylinder; in a practical sense they do
enjoy it; and my engines will enjoy a still greater advantage over the best existing
compounds, but the percentage of absolute loss from the ideal case will be the same.
Nevertheless, as an engine under this process may easily work up to 50 per cent. of
heat conversion apart from this loss, it is a comparatively small matter economically if|
even 50 per cent. more coal should be required because of this internal radiation
loss. But it is still highly desirable to reduce this and all other losses to a
minimum, and it is expected to eliminate this loss almost wholly by the smaller
working interval, and other improved conditions of the engine over those now
in use.
All the elements of the complete series engine process when used in the most
efficient form now known to me and appropriate to this Specification, have now
been explained. The features used may be varied widely and some of them may be

page_text: omitted in selecting a process for any particular engine and locality, when simplicity
of mechanism is deemed of more importance than high economy. Most of the
features described, however, add so much to efficiency and so little to complexity
that it will probably be found desirable to omit them but rarely even from the
simplest engines.
As, however, an efficiency of 50 per cent. is easily within the reach of simple
applications of the process, which requires the combustion of only 0-36 pounds of
coal per H.P. hour, leaving only 0.18 pounds of coal per H.P. hour to be saved by
a perfect heat engine, and as one-half of even this small remnant is saved by
increasing the efficiency from 50 to 67 per cent., it may readily be understood, that
a point is soon reached where it becomes uneconomical to seek further economy at
the present prices of coal by sensibly increasing the bulk or complexity. The
urgent need for better heat engines arises only from the enormous wastefulness of
present types, and most of the possible gain is secured by the first small advances
beyond present limits, say, by doubling the present usual percentage of heat
economy.
It will be understood by those skilled in the art to which the invention relates
that the primary and complete processes above described in their various forms may
be carried out by apparatus widely different in construction, arrangement, and
mechanical details, and that the invention considered broadly is not to be limited
to any particular form of apparatus or of the devices forming parts thereof.
For a full understanding of the invention, however, I have shown in Figures 19
to 42 of the accompanying drawings, simple apparatus of the preferred form for
carrying out the invention in the forms above described, and a boiler which I have
designed especially for use in connection therewith and which forms a part of the
present invention.
I now proceed to describe this apparatus.
In the drawings,
Figure 19 shows, largely in diagram, a substantially complete apparatus embodying
the circulatory system of the general process and its adjuncts in their complete
form but in the simplest case, viz.: with only one boiler and no condenser in circuit,
but provided with a condenser out of circuit.
Figure 20 is a detail of the expansion and supply tank construction.
Figures 21, 22 and 23 are details of the boiler shown in Figure 19.
Figure 24 is a detail of the feeding and regulating attachments of the boiler.
Figure 25 is a detail of the valve controlling the boiler supply.
Figure 26 is a diagrammatic vertical section of the non-circuit evaporative
condenser.
Figure 27 is a detail of the grate shaker connections.
Figure 28 is a sectional detail of the circulating pump, taken on the line - of
Fig. 19.
Figure 29 is a diagram showing the application of the general system to a step
series engine, only the boilers and engines being shown, the heater and other parts
being the same as in Figures 19 to 28.
Figure 30 shows, largely in diagram, a complete apparatus of simple form for
carrying out the series engine process with a single series of seven engines.
Figure 31 is a diagram of a similar apparatus with a transmitter, illustrating the
action of the latter.
Figure 32 is a longitudinal central section of a portion of a boiler showing the
general construction of the boilers shown in Figure 30.
Figures 33 and 34 are cross sections on the lines y-y and z-z of Figure 32.
Figure 35 is a diagram illustrating the interjected circulation.
Figure 36 shows a device for supplying condensing or cooling water.
Figures 37 to 42 illustrate an improved plate boiler for use in the processes and
apparatus above described.
Figure 37 is a side view of one of the boiler sections, showing a simple embodi-
ment of the principle.
Figure 38 is a cross section of the same.

page_text: Figure 39 is a diagrammatic section of the boiler.
Figures 40, 41 and 42 show modified constructions for the boiler sections,
Figures 41 and 42 showing the preferred forms.
The most important features of the apparatus shown in Figures 19 to 28 relate
to the boilers or pressure generators and the condensers or coolers, with their con-
nections to the heater and the attachments for performing the functions pointed out
above as desirable, it being understood that this apparatus may be used with any
particular type of expansion heat engine doing work through the expansion and
consequent cooling of a confined working substance.
Externally the heater H may be of any suitable construction, being preferably
a plain iron box lined internally or externally, or both, with non-conducting
material, as usual in such constructions. The furnace, if for anthracite, is preferably
of the ordinary base burner variety, as shown, provided with the fire box A fed
from the central magazine D, and provided with the rocking grate b. The
cold circulating fluid enters at the base of the heater, passes upward through the
coil of pipes V about the vertical partition C to the top of the heater, thence
downward outside the heater in the pipe V into the annular fire-pot chamber F,
whence it passes upward through the inner vertical pipes V to the top annular or
manifold G, and thence through the circulation pipe V outside the heater onward
to the expansion tank and boiler.
The air supply is regulated externally by any suitable damper to about the
volume required for combustion, but there should be some excess of this supply,
and to effect a more accurate automatic regulation it is preferably sub-divided, the
air which supports combustion entering directly under the grate through passage I,
and a portion which serves to ensure complete combustion, and to dilute the gases
of combustion and check the fire when desired entering above the fire-pot through
the passage 1', these passages being controlled respectively by flap dampers d d².
From the fire-pot the mixed air and products of combustion pass through the
perforated shield e and then are deflected outward by the cone K between the
pipes connecting the annulars or manifolds F, G, thence passing upward over
the partition C forming the inner furnace chamber and downward between and
about the coil of pipes V, entering the flue L at the base of the furnace whence
they escape by the pipe 1'. In case the fires are giving out too much beat, however,
as is assumed in Figure 19, a thermostatically controlled damper ƒ closes L' and
opens a direct connection M for the escape of the gases.
The maximum temperature of the circulating fluid, as above stated, is preferably
regulated by a thermostat, which, together with the attachments by which this
regulation is secured, may be of any suitable form. I have shown, however, a
simple thermostat which will be found efficient and this thermostat is preferably
placed between the heater H and expansion tank T, and in the form shown
consists of a stout wooden rod Th. placed parallel with and adjacent to the
circulating pipe V, this portion of the pipe being formed preferably of a thick
well-lagged brass or copper tube. As the wooden rod does not change in length
with temperature, while the brass or copper tube expands largely and will be
sensibly of the same temperature as the circulation, the relative length of the tube
and rcd gives a positive, simple and powerful thermostat. While the circulating
pipe is shown as part of the thermostat, it will be understood that a tube may be
added to form the thermostat, if desired, instead of using the circulating pipe.
For the purpose of transmitting the movements of the thermostat, a lever N is
pivoted upon the end of the rod Th. with its short arm connected to the pipe V at
the end of the portion used for the thermostat, its long arm being connected by a
chain 10 to one end of a weighted lever g connected by another chain 10* to a bell
crank lever h, from one end of which a connecting rod or rods 11 run to the
dampers d, d'; and from the other end of which a connecting rod 12 runs to the
damperf. By these connections the damper d is closed and d¹ opened when
the temperature reaches the point for which these parts are set and the reverse as
the temperature falls, and the damper fis actuated to open the passage M for the

page_text: products of combustion when the temperature rises to a certain point and to close
the passage M more or less as the temperature falls, the relative times of opening
and closing of the dampers d, d¹f being adjusted as desired, as by lost motion
connections, in case a single connection from the lever N is used. The rod 11 i
shown as passing through a weighted arm on damper d' and carrying a stop by
which this arm is raised and the valve closed against the weight, which operates to
open the damper as the temperature rises. The particular form of the connection>
may be varied to suit mechanical convenience.
b
This thermostat also controls the grate shaker by the connections shown in
Figure 27, the grate 6 being actuated by a crank arm 13 connected by a link 14 to
a crank arm 15 on a crown wheel i, which is mounted in a frame k pivoted to a
fixed part of the construction and connected either to the rod 11, or, as shown for
the sake of clearness, connected by an independent rod 16 to the weighted lever g,
so that the frame k will be raised by the weighted lever as the temperature falls,
and will be lowered by its own weight when released by the lever, as the tem-
perature rises. The crown wheel i, when in its upper position, engages with a
worin driven continuously by suitable connection with the engine or an independent
motor. To prevent excessive wear on the wheel i, which would be caused by the
wheel being brought into contact with the worm gradually, some device is
preferably provided by which the throwing of the wheel i into and out of contact
with the worm shall be instantaneous. In the construction shown, a bent spring 9
is used engaging the end of the frame k, the spring resisting and preventing the
movement of the frame k in either direction until its resistance is overcome, when
the frame moves quickly. An adjusting screw, 50, gives means for regulating the
resistance of the spring catch 9.
A safety valvet controlled by the temperature is preferably used on the expansion
tank T, and this safety valve is shown as actuated from the thermostat lever N by
the following connections. The valve t is normally closed by a weighted arm 47
through which passes a rod 48 connected to the lever N, the rod 48 being provided
with a stop which engages the weighted arm 47 to raise and open the valvet at
the proper time, the valve being closed by the weight when the arm is released as
the temperature falls. The same rod 48 may operate also the three way valve X
controlling the change of circulation from the boiler to the evaporative tank, and
is thus shown, the valve stem 49 being weighted and the rod 48 passing through 10
and being provided with a stop which engages and actuates the arm at the proper
time to open the valve and change the circulation from the pipe V to the pipe V2,
the valve being shifted so as to close pipe V2 and open pipe V to the boiler again
by the weight on stem 49 as the temperature falls. At the lower end of the pipe V³
a valve y is placed, which need only be a check valve of any suitable form
permitting liquid to pass freely downward, but not upward.
It will be understood that all these various valves and dampers for regulating the
maximum temperature and connections therewith to the thermostat may be of any
suitable form, and that the constructions shown are selected only as a convenient
way of illustrating means for securing the desired results. In practice it will be
found preferable in different cases to use single or independent connections from
the thermostat for the various devices, depending upon the mechanical construction
and arrangement adopted for the heater and other parts of the apparatus. The
construction shown, therefore, is simply illustrative and largely diagrammatic.
It will be seen from the above description that this maximum temperature
thermostat as shown, effects the following ends, the order given being that in which
the motions occur, starting as the heat increases, the position of the parts in the
drawing being that at which the temperature has risen to a point where the
regulating devices connected with the heater are brought into action but before
the shifting of the circulation or opening of the relief safety valve.
1. Regulation of the maximum temperature of the circulating fluid through the
fuel supply by disconnecting the grate shaker.
2. Regulation of the maximum temperature of the circulating fluid through the

page_text: air supply by first closing the damper & controlling the air inlet I below grate, and
then opening damper d' controlling the air inlet 11 above grate.
3. Regulation of the maximum temperature of the circulating fluid by opening
damper controlling passage M so as to permit the hot gases to pass directly
upward to the flue L instead of taking the more circuitous downward course over
the heating surfaces formed by the coils of pipes V.
4. Regulation of the maximum temperature of the circulating fluid by diverting
the circulating fluid into an evaporative tank.
5. Regulation of the maximum temperature of the circulating fluid by opening
safety valve positively.
To provide for the remote contingency that the heat shall become excessive after
some or all of these regulative features have come into action or for some possible
disarrangement of the thermostat on which they all depend, an ordinary loaded
safety valve should also be added forming a further safeguard. These several
safeguards may come into action at intervals of five degrees to ten degrees
Centigrade, or other suitable intervals, as may prove to be best in the particular
Each should have its independent adjustments, which once set will rarely
need to be disturbed.
case.
The circulating pipe V passes through the expansion tank T on its way from
the boiler to the heater, and this tank is supplied from the supply tank S, (see
Fig. 20), devices being provided by which the volume of the circulating fluid is
kept sensibly constant regardless of temperature. The preferable construction by
which this result is secured is shown in Figure 20 and is as follows:
A good sized float 1 in the expansion tank T is carried by a rod 2, the float
having a certain amount of free motion in either direction without action on the
valves, but at the limit of the free motion in either direction operating one of two
small valves 3, 5, at top and bottom of the tank, which valves may be of any
suitable form and arranged in any suitable manner so as to be actuated by the
rod 2 in the manner desired. The valve 3 controls a pipe 4 connecting the top of
the expansion tank T with the top of the supply tank S, and the valve 5 controls a
pipe 6 connecting the bottom of the supply tank S with the bottom of the
expansion tank T. If the float rises too high it opens the lower valve 5 and
permits fluid to be blown out by the interior pressure through the pipe 6 into the
supply tank S. If the float falls too low, it opens the upper valve 3, which
permits pressure to equalize in the steam space of tanks S and T, when liquid will
How by gravity into tank T from the tank S through valve or another check
valve 7 connecting pipe 6 with tank T, and opening inward to the tank, or through
both of these valves, until the valve 3 is closed again. Such closure of the
valve 3 results in speedy lowering of the pressure in supply tank S by condensation
and consequent cessation of flow. An air valve 8 may be added in the top of the
tank S to prevent the formation of a vacuum in this tank, and thus to decrease
the quantity of steam which must pass over to equalize pressures. If, however,
the nature of the circulating fluid is such as to generate little pressure, a vacuum
in the supply tank may be found desirable. If it be desired to guard against the
contingency that the valve 5 may be stuck or otherwise inoperative, the valve 7
in addition to its function of admitting fluid from pipe 6 to the tank T, may be so
constructed as to let liquid escape when the pressure in tank T rises above a fixed
maximum. This is not absolutely essential, however, as the tank T should in any
case be provided with a common safety valve, as above stated. The expansion
tank T and supply tank S as shown and described, placed at the top of the system,
secure the regulation of the volume of circulating fluid whether the circulation be
natural under the conditions produced by the heater or produced or aided
mechanically, as by a circulating pump.
From the expansion tank T the circulating fluid passes through pipe V to the
boiler B. This boiler, as shown in detail in Figures 21, 22, 23, consists interiorly
of successive layers of small horizontal tubes n uniformly spaced and preferably
set closely together in layers crossing each other, and almost touching, as shown

page_text: about full size in Figure 23. This gives the boiler proper a square cross section.
as shown in Figure 22, the four sides of the square being tube sheets, occupied by
tubes from top to bottom, the alternate layers, or groups of two or more layers, of
tubes extending at right angles to each other and opening at alternate sides of the
boiler. By this peculiar construction several important ends are attained. 1. The
tubes are more closely spaced than is otherwise possible, since holes for only
each alternate layer occur in each tube sheet so that the holes for the tubes do not.
interfere with each other and uniformity of spacing may be readily assured.
2. Each tube stays a nearly constant and small area of tube sheet and for each
such area there is a tube to stay it, so that the tube sheets may be thin and of
constant thickness regardless of the size of the boiler, providing that the size and
spacing of the tubes remain constant. 3. The interual evaporative conditions are
better than with parallel tubes. 4. The boiler may be constructed by pan brazing
of the tubes, and the corners also may be brazed at one dip of each face. The
vertical corners are merely rounded to overlap as shown in Figure 22, and brazed
together at the same time as the tubes and the top and bottom of the boiler are
brazed onto the sides at the same time, being shaped as described hereafter.
The square boiler thus formed is slipped inside of a cylindrical casing p which
may be of any thin sheet metal, if the circulating fluid be not circulated under
pressure. If it be so circulated the casing must be of thickness adequate to resist
the pressure.
In slipping in the boilers some form of spring contact is preferably
effected at two opposite corners, and preferably also at the remaining corners,
which makes these corners practically water tight against any trifling pressure.
It is not necessary that they should be absolutely water tight. Also, before the
boiler is slipped into the casing p, certain thin segmental plates 17 are added either
to the outside of the boiler or to the inside of the casing, thus forming partitions
dividing the space about the boiler within the casing into chambers, these partitions
having preferably spring or feather edges, which makes them practically water
tight against any trifling pressure. It is not necessary that they should be
absolutely water tight. The upper partition 19 is the same as the others, except
that, with the construction shown, it is not flat but curved so as to cover the ends
of the tubes which fill the upper portion of the boiler under the concave cap.
The caps 18 on the outer casing are then put on, these caps being preferably
shaped so as to be sections of a sphere having a radius equal to the diameter of the
casing, so that they will be of equal strength therewith, if of the same thickness.
The two boiler ends are preferably of the same form and radius as the caps, but
need a thickness proportional to their size regardless of the thickness of the tube
sheets, since they are not stayed by tubes. They may also need to be tied together
by more metal than is contained in the tube sheets, which may be effected by
tubular or other stays at the corners, which may also serve to effect the spring
contact at these corners above referred to. Each of the caps is also provided
with a central opening or pipe through which the circulating pipes V, and Vi
connect at top and bottom with the interior of the casing p, the circulating fluid
entering at the top of the casing and leaving at the bottom. Through this opening,
also, enters the boiler feed pipe 20 at the bottom of the casing and from the top
issues from the boiler the steam pipe O.
When the boiler is thus constructed, the dotted lines in Figure 21 indicate the
path of one portion of the circulating fluid in passing through the boiler. This
fluid enters at the top and fills what is in effect a top storage chamber above the
boiler within the casing, from which there are only two openings, viz.: two of the
segmental areas between the boiler and the casing above the top partitions 19,
each of which areas give access to one or more of the upper layers of tubes.
Dividing between these in about equal volume, the circulating fluid in two
distinct masses follows the zigzag path indicated by the arrows and a path at right
angles thereto until it reaches the bottom chamber, wherein the two masses reunite
and pass out through the cold circulating pipe V at the bottom of the casing and
thence pass together to the next boiler if two or more boilers are employed, or to

page_text: one or more condensers, or return directly to the heater, as in the construction
shown in Figure 19. The number of possible partitions 17 is limited only by the
number of layers of tubes n. The more partitions are used the faster must be the
current to pass a given mass of circulating fluid per minute, and hence, as
experiment indicates, the higher the transmitting efficiency of the surfaces in a
ratio approximating to the square root of the velocity. It is expedient, therefore,
to have as many of these partitions as mechanical convenience permits.
There is a surprising absence of any tendency to foam in boilers constructed as
described, despite the close spacing of the tubes which would seem to insure it.
The differential temperatures of the circulating fluid corresponding to the different
layers of the working substance seem to prevent this. The boiler is also so small
that any attempt to increase its steam generating capacity seems almost superfluous.
Nevertheless, foaming may at times result with some working substances, and this
may be prevented and the effective heating surface per cubic foot substantially
increased at the same time by interposing between each two layers of tubes and in
contact therewith a sheet of fine wire gauze as shown in Figure 23 at 100, having
from 30 to 60 meshes per inch (12 to 24 per centimeter). This gauze does not
diminish the effective opening for the passage of the working substance upward.
On the contrary the proportion of open space to total area is about the same in
wire gauzes of all commercial sizes as exists between the tubes at the middle
thereof, but the addition of the gauze does insure that every particle of steam and
liquid shall be repeatedly in immediate contact with hot surfaces as it rises;
because the gauze sheets are in immediate contact with hot tubes both above and
below them and both by radiation and conduction will be supplied in all parts with
heat which they will surrender to the working substance as it passes them, as
effectively as do the tubes themselves.
The one serious objection which applies to the use of such gauze applies also to
the boiler itself without the gauze. The surfaces are so small and so closely spaced
and the quantity of liquid evaporated per cubic foot and per square foot of surface
is so very great, that the slightest impurities in the working substance will tend to
accumulate rapidly, coating the surfaces and clogging the interspaces, if each mass
of working substance is used only once. Against this there is the compensating
advantage that, as the boiler is exposed to low temperatures only, these deposits
are not likely to cake on, as in fire boilers, but for a considerable time at least
will remain in a soft and pulpy state. so that they may be blown out by a reverse
current through a blow-off valve in the usual way. Also, the cubic contents of the
boiler are so small that no great loss of time or heat ensues from blowing off
very frequently. In this manner any tolerably pure water supply may be used
in open cycle without condensers. Nevertheless, the only entirely effective
precaution against these deposits is to use condensers always, whether a vacuum
is desired or not, for the mere sake of using the same working substance over and
over.
The branch pipes 21, 22, connecting respectively with the feed pipe 20 and
steam pipe O, form the means of attachment for several boiler adjuncts, which are
preferably employed and connected substantially as shown in Figure 19, and in
detail in Figure 24. These adjuncts include an ordinary safety valve, a steam
gauge 23 and an ordinary water gauge 24. The safety valve is not shown, as it
may be of any common construction. It practically never opens, and is preferably
a meie leaf spring closing an aperture in pipe 22, or steam pipe O. The steam
gauge 23 and water gauge 24 will not be so steady, if connected as shown, to
branches of the steam pipe and feed pipe, as if connected to separate apertures in
the boiler itself, but the construction shown is sufficiently convenient to overbalance
this disadvantage in most cases.
A charging can 25 for adding to or subtracting from the constant mass of fluid
which, in the construction shown, is circulated in closed cycle between the boiler,
engine and condenser, is also shown, this can having a separate water gauge 26.
When a condenser is used, this adjunct is not needed, and its use is always rather a

page_text: convenience than a matter of importance, but it is preferable to employ this can
with the connections shown rather than to rely on a pump to pump liquid in or out
of the circulating mass of working substance. At the top, the charging can 25 is
connected with the steam pipe by the pipe 22 controlled by the cock 28, and at the
bottom it is connected with the feed pipe 20 through the pipe 21 and a pipe 29
controlled by a cock 30. Liquid is introduced into the charging can 25 by the
funnel m. As it may be noxious or highly volatile, this funnel is preferably
provided with an interior female thread into which a nozzle may be screwed to give
an air-tight connection, and a similar cock 31 is provided at any suitable point for
drawing off liquid from the charging can. This charging can must be made strong
enough to resist any boiler pressure, but need not be large. To remove liquid
from the system into the charging can the cock 30 is opened, when the interior
pressure in the system will blow back as much liquid as desired into the can up to
its full capacity, with or without a slight opening of the cock m to release any
confined air or gas.
To introduce liquid into the system the cock 28 is first opened
letting boiler pressure into the can, and then opening the cock 30 allows the liquid
to flow into the boiler through pipes 29, 21, by gravity.
A water blow-off valve 27 acting antecedently to the safety valve is preferably
used, through which an excessive boiler pressure will blow back all liquid in the
boiler into the condenser or elsewhere and thus secure a regulation of the maximum
pressure in the boiler independently of the safety valve. This water blow-off
valve 27 may be of any type which opens at a fixed interior pressure and closes
when that pressure ceases and may be introduced at any point where it is in open
connection with the bottom of the boiler, either on the boiler, or a branch pipe as
shown.
34
The supply of water to the boiler is regulated in the construction shown, by the
control of the steam supply to the feed pump according to the water level of
the boiler. This control may be secured by any suitable means but a simple and
efficient construction of regulative valve is shown. This regulative valve is used
in cases in which the feed pump is an independent mechanism driven by an
independent steam supply, and any suitable pump of this character may be used.
The feed pump may draw the water from an external supply or from a condenser,
as shown.
When it draws from a condenser, this regulative valve may not be
found necessary.
As shown, the compound pipe 33, 34 constitutes in effect an
ordinary water gauge automatically controlling the steam supply to the feed pump,
pipe 33 being in open connection with the water space through pipe 21, and pipe
with the steam space through pipe 22. From the chamber at the top of pipe 33,
a small steam pipe 35 leads to the feed pump P11 and 36 is a small ball float in
this chamber, this ball float being arranged to close pipes 34, 35 and cut off the
steam supply in its top position and open them to supply steam to the feed pump
when lowered by the fall of the water in the boiler and pipe 33. It is not
necessary that this ball float should have a very tight seat, as any small amount of
steam leaking by it will condense instead of operating the pump. In the steam
pipe 35 a pressure reducing valve of any suitable form should ordinarily be added
to stop the pump by the resistance at a certain pressure in the boiler and prevent
any more than a desired maximum working boiler pressure.
The circulating fluid may pass from the boiler B to another boiler or boilers or
other devices for utilizing the heat, and then return to the heater directly or
through one or more condensers or, as in the simple construction shown in
Figure 19, return directly from the boiler to the heater. In this construction the
circulating fluid passes from the boiler through the pipe V₁ to a circulating
pump P which, as shown, consists of a chamber or enlargement on the pipe V' in
which runs a screw or other force pump Q which may be driven in any suitable
manner, a belt and pulley being shown for this purpose. Upon the pipe Vi
between the boiler and circulating pump P is placed the cold or minimum
thermostat Th¹ by which the speed of circulation of the circulating fluid and
consequently the minimum temperature is controlled, this thermostat being of.
G

page_text: same construction as the maximum thermostat T₁, and consisting of a wooden rod
on which lever N¹ is pivoted, this lever being connected to the pipe V₁ at a short
distance from the pivot, and its outer end being connected to and operating a
lever 37 which is connected by a link 38 to a valve, which is preferably a sliding
grid-iron valve, as shown, controlling the by-pass 39 which extends from the front
to the rear of the screw Q within the chamber on pipe V. The position of this
valve determines the proportion of liquid which will simply circulate around in the
by-pass 39, and that which will follow the regular circulating pipe V₁. This last
takes considerable power while the short circuit through the by-pass takes
practically none, so that the required regulation of speed is secured without any
regulating valve on pipe V₁ or means for varying the speed of the screw Q. The
latter varies directly with the speed of the engine at all times, so that it is fairly
well graduated to the requirements without special mechanism.
When the temperature falls to the minimum, this valve 38 closes the by-pass so
as to increase the speed of circulation. As the temperature rises the valve is
opened so as to allow a part of the circulating fluid to pass through the by-pass 39
from front to rear of the screw, and thus check the speed of circulation, and
decrease the amount of heat delivered by the circulating fluid to the boiler. The
valves is preferably constructed and connected to the thermostat so as to practically
stop the circulation as soon as drawing of steam from the boiler stops.
The circulating fluid for the jacketing of the engine cylinders may be taken from
any convenient point on the hot circulation. As illustrated a small pipe 51
connects the circulating fluid chamber at the top of the boiler with one end of the
jacket u about the engine cylinder E, which jacket may be of any suitable con-
struction to secure the proper circulation of the liquid in the jacket, and a pipe 52
connects the other end of the jacket with the cold circulation pipe V₁, the jacketing
fluid thus circulating with the main body of fluid.
Any suitable form of condenser may be used in connection with apparatus for
carrying out my improved method, and the form of the condenser will depend to
some extent upon the special form of such apparatus and the manner in which the
condenser is applied. The condensers used on the circulating system and out of
circuit may and preferably will be of different forms, specially adapted for these
different uses. When the condenser constitutes a part of the circulating system,
that is, when the circulating fluid itself is the cooling substance in part or in whole,
as it is supposed to be for engine all, Figure 3 and a', Figure 4, and as shown in
Figure 8, it will be placed on the cold circulation pipe at any point between the
cold thermostat and heater, and preferably is of the same type as and may be a
mere duplicate of the boiler above described, and the condenser C of Figure 8 is
of such a construction. If the direction of all the arrows in Figure 21 be changed,
Figures 21 to 23 will represent the construction and action of such a condenser,
the circulating fluid entering cold at the bottom of the condenser and passing out
heated at the top and the steam entering the condenser at the top and passing out
condensed at the bottom. Also, when the condenser is out of the circulating
circuit, that is, when it is served by an external cooling fluid, whether air or water,
a condenser of similar construction and action may be used. If such cooling fluid
be air, the dimensions of the condenser must be greater than if it be water, but the
construction shown in Figure 21 furnishes a highly effective air cooler or condenser
of this type without further change. The effectiveness of this construction as an
air condenser, however, may be materially increased by interjecting with the air
through the pipe 20 a liberal spray of water. This will be vaporized as it passes
through the tubes, absorbing much or all of the heat, the air blast in the latter
case serving only to carry through the water mechanically.
With such condensers, however, the impurities of the water evaporated to effect
cooling will be deposited in the inside of the tubes, whence they can be removed
only by removing the cylindrical case of the boiler. For this reason I prefer for
the condenser out of circuit, the type of evaporative condenser shown in partial
diagram in Figures 19 and 26, which condenser and the method of condensing

page_text: employed therein form in themselves parts of the invention. The condenser
consists in the simple form shown, only of a shallow open box filled internally
with superposed gridirons of tubes 40, the end tubes being connected together at
each alternate end by a right and left pipe joint 41, or other simple connection.
This box has double bottom 42, the inner one of which is perforated, and a false
perforated top 43 and is filled with water so as to submerge the latter. Instead of
using superposed gridirons, long tubes may be bent into vertical serpentines, being
connected by cross tubes at their upper and lower extremities only, or corrugated
or other plate surfaces may be used.
The exhaust from engine E passes through pipe R to the condenser, entering
the pipes 40 at the top, and the condensed water leaves pipes 40 at the bottom of
the condenser through pipe 44 forming the suction pipe for feed pump P" by
which the feed water is delivered through feed pipe 20 to the boiler. By some
small pump P, water is continuously withdrawn from above the false top through
pipe 45 and forced in between the double bottoms 42 through pipe 46, so as to
promote a rapid and somewhat violent circulation, the water rising through the
perforated top 43 in jets to a height regulated by the force of the pump, which is
graduated to produce the desired rapidity of evaporation. The rate of evapora-
tion may be further materially increased by a wind or blast of air across the
surface from a pipe or pipes 53, and thus the temperature of evaporation may be
kept down to a low point; but without any such blast of air, the working substance
may be condensed at its boiling point under atmospheric pressure, or
a little
above it, so as to give the equivalent of a non-condensing engine thermo-
dynamically, while still using the working substance over and over in closed cycle.
A box a little over three feet (1 meter) square and some teu inches (+ meter)
deep will easily give a condenser of this type of 50 H.P. capacity, the quantity
of condensing water used being approximately equal to the quantity of steam
condensed, regardless of the degrees of vacuum obtained; the latter depending
solely upon the rapidity of the surface evaporation produced by circulation of the
cooling liquid and a surface blast of air. As both of these are so easily obtained,
there is no motive for neglecting to obtain an excellent vacuum, even though the
primary motive for using the condenser is to use a single mass of working
substance over and over. The cylinder and slide valve lubricants, if of a light
and greasy nature, will tend to accumulate objectionably in the condenser. For
this reason I prefer graphite as a lubricant with or without the admixture of a
small quantity of heavy grease, and I have found this to answer admirably as a
cylinder and slide valve lubricant, with but very slight escape of lubricant in the
exhaust.
The step-series engine apparatus will now be described in connection with
Figure 29, which shows such an apparatus of simple form, the step-series system
being substituted for the boiler and engine system shown in Figures 19 to 28 and
the heater and some other parts being omitted in Figure 29, as already fully
described.
In this apparatus the steam from the boiler B passes through the pipe O to the
first engine E and the exhaust from this engine passes through the pipe R to the
boiler-condenser B' C, from which the condensed steam is pumped back to
the primary boiler B through the pipe 20 by the pump P¹. The steam from
boiler-condenser B1 C, passes through the pipe O' to the second engine El and
the exhaust from this second engine through the pipe R' to the second boiler-
condenser B C¹ from which the condensed steam is returned to the first boiler-
condenser through the pipe 20 by the pump P. The steam from the second
condenser-boiler B C passes through the pipe O2 to the third engine and
the condensed steam is returned to the second boiler-condenser through pipe 20,
and so on through any number of steps to the final boiler-condenser from which
the steam passes through the pipe O to the final engine E" and the exhaust through
the pipe R to the condenser C, the condensed steam being returned through the
pipe 20 by the pump P. This final condenser C is preferably of the same

page_text: size and form as the boiler-condensers and uses any suitable condensing fluid which
is admitted through the pipe shown at the bottom and passes out of the top of
the condenser. The gases of combustion are or may be passed through or around
the successive boilers by extending the stack L of the heater by a pipe L'
through the steam space at the top of the boilers, as shown in dotted lines, care
being taken not to permit the temperature of these gases when thus used to rise
above a certain moderate and regulated temperature, which may be secured either
by manual or automatic regulation. The return of the condensed vapor from the
boiler condensers through the feed pipes 20 may be omitted on some or all of
the boiler condensers, if found desirable for any reason. The volume of working
substance is controlled by the same means as previously described. The blow off
valves 27 are the same as previously described and are shown as arranged to blow
back the liquid into the succeeding boiler-condensers.
In Figures 30 to 36, a series engine apparatus is shown employing a gas heater
and a single series of engines and condensers, this form of heater being shown as
desirable and for the purpose of illustrating different forms of heaters which may be
employed in carrying out the invention. It will be understood, however, that the
solid fuel heater previously described may be used in this series engine apparatus or
this heater in the apparatus previously described, or any other suitable heater may
be used. The gas heater is especially applicable to the form of series engine
apparatus shown, however, which uses a double or liquid and gas circulation, the
gas being the fuel of the heater and its air supply.
Referring now particularly to Figure 30, which shows a construction corre-
sponding to the diagram, Figure 9, the working substances of the successive
engines a to g are assumed to work in closed cycle between the boilers and condensers
for the respective engines, being returned from condenser to boiler by the
respective pumps P. to P. The engines a to g are shown in diagram only, and
the pumps P. to P, likewise, as these and their connections may be of any suitable
form:
The liquid circulating fluid passes through the condensers C₁ to Cg and the cold
circulation pipe V₁ to the heater H, where it is heated, and passes thence through
the hot circulating pipe V and the expansion tank T to and through the series of
seven boilers Bg to B, and then through circulation meter M*, circulating pipe V',
circulating pump P and cooler C to the series of condensers again to repeat the
circuit. The liquid circulation is shown as passing successively through three
concentric coils of pipe in the beater H, first upwards, then downwards, and upward
again from the inner to the outer part of the heater, thus being exposed successively
to hotter and hotter temperatures.
The air circulation, for simplicity of illustration, is assumed to be already
mixed with the fuel gas before entering the system and enters from the external
supply through the pipe W₁ at the cold end and thence passes in passageways
through the tops of the successive condensers from the cold condenser C, to and
through the hot condenser C, and thence through the pipe W₁ to and through the
heater. After combustion within the heater, the air circulation is passed up, down
and up again by partitions 11 past the concentric coils of pipe V for the liquid
circulation, and thence through the pipe W and passageways at the tops of the
boilers from the boiler B. to B. At the cold end of the hot circuit, the gases will
or may be so cooled down as to be passed through a suction fan F, by which
circulation is produced, and thence be discharged into the atmosphere without the
aid of any chimney, which is more economical of heat than to use
chimney draught, although it will be understood that the latter may be used if
desired. In order to keep a correct engine log, the gas supply, and preferably the
air supply also, should be metered. In the construction illustrated, this is effected
by a meter M¹ on the pipe W¹, before entering the system.
a natural
It will be understood that this air circulation may be carried through the
condensers and boilers in suitable passageways outside the shells, as before stated,
and it may be found that the mechanical convenience of such construction may

page_text: overbalance somewhat its functional inferiority, on account of the small area of the
external surface of the condensers and boilers and the fact that the air circulation,
being ordinarily the hottest, should be applied in the upper parts of the boilers for
the best functional action, while if carried outside the condensers and boilers the
whole surface of the latter is used.
The maximum temperature of the gas circulation, that is, its temperature on
entering the boiler circuit, requires no special controlling devices with a gas flame
as shown, as this can be regulated once for all in the design of the heater, gas
flames burning at a given rate giving always the same temperature. The maximum
temperature of the liquid circulation, that is, its temperature on entering the boiler
circuit, is regulated in the construction shown by regulating the fuel supply by a
thermostat, controlled by the temperature of the circulating fluid between the
heater and expansion tauk T, the thermostat being the same as previously described,
the thermostat lever N being connected by a rod 12 to a cock 13 on the air and
fuel supply pipe W', so that this thermostat controls the cock and supply of fuel
in accordance with the temperature of the liquid circulation, so as to secure the
It will be
desired maximum temperature of the hot circuit and no more.
understood that this maximum or hot thermostat, when used with the hot interval
or heating engines, or both, will preferably be placed between the heater and the
first boiler in series.
The minimum temperature of the liquid circulation on the hot side, that is, the
temperature on leaving the boilers and before entering the cooler, which temperature
determines the amount of heat abstracted in the boilers, is shown as regulated
by regulating the speed of circulation, by a thermostat Th¹ controlling the
valve S as in the construction previously described. This cold thermostat is
set to give the desired working interval for the cold engine a above the minimum
temperature for the time being. It will be understood that the minimum or
cold thermostat, when used with the cold interval engines previously described
is preferably placed between the boilers in series and the cold interval engine
boilers.
The cooler C is shown as of the same construction as the condensers or boilers,
but somewhat larger. All that distinguishes it from either is that a cooling fluid
enters through the usual aperture for working substance, passes down through the
interior space for working substance where it absorbs heat, and thence passes out
as if a working substance. From the nature of its functions, either the direction
of the currents or the allotment of passages may be reversed, that is, the circulating
fluid may pass either down or up, the cooling fluid then passing in the reverse
direction, the passages being interchanged. The cooling fluid is shown as entering
at the top through the pipe S¹ and leaving at the bottom through the pipe S.
Usually the cooling fluid will be at a substantially constant temperature from
day to day. The setting of the cold thermostat should then also be constant from
day to day and the part Th¹ should be of wood or other substance which does not
expand with heat. It may at times happen, however, that the cooling fluid varies
considerably in temperature from hour to hour which will result in a varying cold
interval, or compel the constant resetting of the thermostat. This inconvenience
is readily avoided, however, by substituting a metallic pipe for the wooden rod and
passing the cooling fluid through this rod on its way to the cooler, and Th' is shown
as a part of the pipe S¹. Thus the cold thermostat will maintain the constant cold
interval to which it may have been set.
If we conceive the cooling fluid passing through the cooler C to be the circulating
fluid at the bot end of another and colder series working below that shown in
Figure 30, the cooler C becomes a transmitter without any mechanical change. In
Figure 31, such a construction is shown in diagram, the hotter series B being that
shown in Figure 30 and the colder series A that supposed to be below it.
In this
case, the air circulation is simply carried through the pipe W₁ from the colder to
the hotter series and returns through the pipe W from the botter to the colder
series, as if they were merely one series, as in fact they are, the transmitter

page_text: having no dynamical significance. The liquid circulation of the cold series A
circulates in the pipe Vexactly the same as the liquid circulation of the hot
series B, excepting that at the hot end, instead of passing through a fire heater it
passes through the transmitter C T', which is at once the cooler of the hotter
series B and the heater of the cold series A, C' being the cooler of the cold series.
There may or may not be a series meter M and cold thermostat in connection with
the transmitter, as shown; preferably there should be, but it is not essential.
The general construction of the series engine boilers, in one of the forms which
may be used, employing tubes, is shown by Figures 32 to 34 inclusive, but the
details, of course, may be varied almost indefinitely. In Figure 32 the arrows 1
show the hot air circulation, which theoretically is carried straight from boiler to
boiler and at the top of each, because it is the hotter part of the circulation, but in
practice this course for mechanical convenience may be deviated from, as shown
by these arrows, and the hot air circulation taken outside the boiler sheets to
carry it from boiler to boiler either in a direct passage, as indicated by the dotted
pipe and the upper semi-circular arrows, or caused to circulate around and jacket
the cylinders before returning to the boiler circuit, if desired. The liquid
circulation may be used in place of the air for jacketing, and is the better of the
two for this use, except that the air may be at a somewhat higher temperature.
The arrows 2, 2, show the general course of the liquid circulation, which, as
previously stated, is preferably entered at the top and worked downward by a
zig-zag path to an exit at the bottom. Three returns are shown, but more than
three are ordinarily expedient, and any number from two to even twenty or more
may in different cases be used. The zig-zag downward course of the circulating
fluid is adopted to increase its possible speed, which at best is slow. By using
vertical instead of horizontal tubes, the functional necessity for using zig-zag
passages will disappear, but the possible speed of the circulating fluid will be
injuriously curtailed, and horizontal zig-zag passages or some equivalent are
preferable.
The tubes are omitted in Figure 32, for clearness, but as shown in the section
Figure 33, the space between the tube sheets is filled with a solid mass of tubes 3
for the circulation, the black tubes 4 being steam pipes shown as perforated to
receive the steam evenly. The tubes above the line 5-5 are for the not air
circulation, and the tubes between the lines 5-5 and 7-7, between 7-7 and 9-9,
and between 9-9 and the bottom of the boiler, in Figure 34, are for the successive
returns of the liquid circulation. The intersticial space between these tubes is one
open chamber for steam and liquid. No particular water line is either shown or
intended. Liquid enough to furnish steam for one (or n) strokes is caused to enter
through the feed pipe 16 by the pump at each (or every nth) stroke, the steam
passing out through the perforated pipes 4 and main steam pipe 17.
The boiler steam pipes 4, 4, may all be in one row or have any other
arrangement, or may be omitted entirely and the steam taken out from a single
opening at the top, but it seems preferable that the steam exits should be
somewhat scattered along the hot air pipes, in order to promote perfect super-
heating and even evaporative action.
In Figure 32 the barrel of the boilers B, B, is shown as faced at each end by a
solid partition 6, 6, which should preferably be made non-conducting.
The
circulation chambers through which successive series of tubes 3 connect at the ends
of the boilers are formed by plates 5, 7, 9, air circulation entering the chamber
above the top plates 5, and the liquid circulation entering the chamber below the
plates 5 from the base of the boilers through circulation pipe 18 from the base of
the next boiler, and passing successively horizontally and downward through the
pipes and lower chambers to the base of the boiler, where it passes to the next
boiler through pipe 18. Both the gaseous and liquid circulation are shown as
carried from boiler to boiler by exterior connections, the gaseous by the upper
dotted passages 19, and the liquid by the lower circulation pipe 18. Although
shown in Figure 32 for convenience as placed centrally at the top and bottom of

page_text: the boiler, both of these passages should, as a rule, lie at one side of the center, as
correctly shown in the diagrammatic sections Figures 33 and 34, in order that the
total space occupied by the circular boiler and its appurtenances may not exceed,.
or not much exceed the dimensions of an exscribed square about its boiler circle.
The boilers may then be stacked up one above the other indefinitely without
6acrificing compactness; the proper manner of multiplying boiler power being
rather by an indefinite multiplication of small units than by specially designed
large units.
The application of this principle is subject to many practical
limitations, but as a general scheme I contemplate producing all boilers from
precisely the same size of boiler shell.
The solid face-plates 6, 6, are expedient for a number of reasons, but chiefly to
make it easy either to cut out any defective boiler permanently, or to remove it
for renewal or repair, and to replace it again, all without stopping the engine,.
or more than one engine. To this end and other ends one ог more by-pass
pipes 20 forming continuations of the circulation pipes 18 should be preferably
carried along past every boiler, of sufficient size to pass the circulation outside
of that boiler. They should be connected with the circulation pipes 18 by a
valve or three way cock 21, which for clearness is shown functionally only. With
these valves in the position shown in full lines in Figure 32, the by-passes 20
are inactive. By throwing the two valves 21 at opposite ends of any boiler up
into a horizontal position, as indicated in dotted lines in Figure 32, that boiler
is cut out of the circulation, and the circulating fluid flows past it in the by-pass 20.
The by-passes may or may not be filled with inert circulating fluid, but to save
annoyance from possible leakage of the valves they preferably should be so filled.
A precisely similar by-pass and valves may be provided for the air circulation
to connect the passages 19 at opposite ends of the boiler which are also preferably
connected from boiler to boiler by some cylinder jacketing passage.
It will
probably be found unnecessary, however, to provide the boilers with permanent
by-passes for the air circulation, as they will seldom be used, but temporary
pipes may be inserted when desired to remove the boiler. By cutting out both
the air and liquid circulation any boiler may be rendered inert for examination
or repair, and it may be removed without interfering with the other boilers.
will be obvious, however, that those by-passes are in the nature of a convenient
adjunct for occasional use, and in no way necessary to the functional action of
the boiler when in service. They may, therefore, be omitted.
It
It is to be remembered that, except when water or other liquid is circulated
under pressure to raise its boiling point, all the circulatory passages are under
only the very slight pressure needed for circulation, and therefore the joints need
not be very tight. Every joint about the boiler, including the tube sheet joints,
can be made perfectly well by brazing, if the boiler is of copper; or by equivalent
process for other metals. The theory and construction shown and to be shown
does not permit more than a few degrees excess over a fixed maximum temperature
in any boiler; but as a rule, for mechanical reasons, all the boilers should be
made to stand the highest temperatures. The joint between plates 7 and 6, and
between 9 and 6, need not even be made perfectly water tight. That between
plates 5 and 6 should be so, but need not stand much pressure.
The
The condensers are throughout mere duplicates of the boilers, save only that
the arrows showing the direction of the circulation should be reversed. In
Figures 32 to 34, regarded as condensers, the steam to be condensed then enters
through the steam pipe 17 and 4, and works its way downward through the
circulation pipes 3 to the bottom, before reaching which it is condensed.
high pressure of four to five atmospheres at which the steam will ordinarily
condense ensures its forcing its way promptly into every point where there is a
partial vacuum, i.e., where the surfaces are not doing enough work, without the
aid of any open spaces between the tubes. It is only in attempting to condense
to the zero of pressure that trouble from imperfect distribution of the steam to
the surfaces arises. Then it naturally arises, as the total absolute pressure of the

page_text: attenuated steam is but little more than a change of 1° C. will produce in steam
of five atmospheres' pressure.
In the condensers as well as in the boilers it will be
seen that the hottest temperatures are at the top and the coldest at the bottom.
The air circulation will generally be hotter than the liquid when it enters the cold
circuit; and as it is exposed to the first impact of the entering steam it is pretty
sure to become so, if it is not at first.
In Figure 35 is shown in diagram an arrangement of the condensers for cold
circuit emergency increase of power by an interjected circulation as already
explained, this being provided for by connecting the condensers by pipes 22, for
the circulation 2 passing outside the condenser shells, and adding a series of
by-pass pipes 23 arranged in the same way as by passes 20 and provided with valves
similar to valves 21. Some or all of the condensers are provided also with other
pipes 24 similar to pipes 22 and connecting the condensing passages, and with
by-passes 25 connecting said pipes, these by-passes being controlled by valves
similar to valve 21. These pipes and by-passes are for a cold water circulation 2ª,
shown in dotted lines.
If an emergency arises for more power, the regular circulation of one or more of
the condensers, C. and Ca, as shown, is cut out into their by-passes 23, and the
cold water circulation cut into these condensers from by passes 25 through
pipes 24. These condensers may be first drained of their circulating fluid, or this
will be driven out by the water circulation and voided externally, if not previously
drained. If it is desired to provide only for a moderate increase of power, a few
condensers only may be thus fitted up, but Figure 35 shows all the condensers thus
fitted. There is no serious objection to providing for the use of this power to the
full extent in marine or other engines having use for it.
Ordinarily it is not expected that the condensing pressures will be more than
half the boiler pressures, if so much. In this case, doubling the power is the
utmost to be gained by this interjected circulation, unless the engines are especially
designed for a greater excess. There is no reason, however, why the engines should
not be designed to give three or four times their usual power in emergencies, nor
is any sacrifice of the usual working economy involved in so doing, barring
thermodynamic fractions.
The injection water required for the coolers, cold interval condensers, and for
this interjected circulation is used under quite different conditions from those of
the ordinary condensing engine, that is, in a steady stream through passages of
approximately uniform cross-section without any pockets in them for air to collect
in and so without any necessity for an air pump. It will probably be found
preferable, therefore, at least in all marine and pumping engines, to obtain and
circulate the supply of this liquid by devices acting on the well-known jerk-water
principle, and many different arrangements may be used for this purpose. A simple
and efficient construction is shown in Figure 36 in which 26 represents the hull of
a vessel, preferably near the bottom, where the water is colder, and well forward
where the water will be less disturbed by skin friction. The passage S¹ is continued
to form the jerk-water passage and terminates in a scoop 27 shown in position for
use and out of use in full and dotted lines respectively. When the ship is in motion
the water impinging upon it in the direction shown by the arrow, tends to open the
scoop 27 further, a tendency which is resisted by the rod 28 ending in any form of
stop 29.
If any rupture of the passage S' occurs it is only necessary to stop the
head way of the ship, and to have the check rod so constructed as to resist tension
only, when the scoop 27 will close of itself and thus stop the inflow. The
construction shown therefore is better than the ordinary injection pipe, which if
ruptured can only be closed by a valve and sometimes not at all. By adding at
the voiding end of the passage S₁ what we may call a suction jerk-water
constructed exactly the same as in Figure 36, except that it points in the reverse
direction, and that the rod 28 is adapted to resist compression rather than tension,
the velocity of the water in S¹ may be greatly increased to something like the
velocity of the vessel. Such high velocity can hardly be required, but we thereby

page_text: gain the further advantage that the pipes may be of uniform cross-section, since
the velocity is uniform, regardless of lift, while in the construction shown the pipes
must enlarge regularly upwards so that their cross section may be in inverse ratio
to the decrease in the velocity of the water due to the lift. The same method of
securing and circulating the supply may be used wherever there is a moving stream
of water in a pipe, with or without the further aid of a pump, by borrowing water
from a main and returning it again uninjured, except that some heat has been
added to it. By this method of supply, the loss of power involved in alternately
stopping and starting the cold water supply at high velocities, as is done twice
by the ordinary air pump, is avoided.
In pumping hot liquids, as must be done through quite an unusual range of
temperatures between the boilers and condensers, the proper precautions must be
taken to avoid trouble from lack of good suction. For this reason, instead of
any form of mechanical pump, I prefer to use the pressure of steam directly
somewhat on the pulsometer principle to effect the return of working substance
to the boiler. Cylinder lubrication is likely to be a cause of some trouble unless
properly managed, especially when working substance is worked in closed cycle.
So far as possible this trouble should be avoided by using working substances
which are in themselves lubricants. If lubricant be used, graphite mixed with a
little of the working substance furnishes a suitable one.
'The valve gear may be
of any simple type since the usual economic motives for using the Corliss and other
more complex valve gears are absent. Safety valves of the ordinary type arranged
to open and close frequently and discharge large quantities of steam are not needed,
as the working pressure is very nearly the maximum which can arise, except in
case of some accident. In lieu thereof, there may be provided some form of simple
relief valve, spring loaded and set to discharge into the air circulation and to make
enough noise to attract attention when doing so. If, as is preferable, the
temperature is strictly controlled throughout, these are little likely to come into
action. Leaks of working substance into the circulating passages are not likely
to be detected at once unless by the noise of a fall of pressure.
The only
effect of such a leak is gradually to drain the boiler of working substance and stop
efficient action.
The readings of the liquid meter in connection with the thermometer readings of
the highest and lowest cold and hot temperatures of circulation give an absolute
measure of the quantity of heat supplied to the engine during any given period.
If there be an air circulation also, and the air supply be metered, thermometer
readings in the air circulation at the same points will give an absolute measure of
the quantity of heat supplied to the engine through that circulation, except when
non-condensing engines deriving heat from a source external to the heater are
exhausting into the circulation and in that case a practically exact measure of this
extra heat can be obtained by metering the water supplied to such engines. By
inserting thermometers in air and liquid circulation between each engine a similarly
exact record of the work done by each engine, given directly in form of thermal
units converted into work, will be obtained by simply multiplying the value of
mass V as shown by the meter readings, by the difference of thermometric or
thermostatic readings. Thus any irregularities in the workings of the several
engines may be at once detected and corrected, as for example, a too volatile or
unvolatile working substance for the best work with any engine.
The customary method of expressing efficiency in terms of the weight of steam
used per hour is impossible with any type of engine under this series engine process.
The quantity of steam passed through each engine may of course be observed
experimentally, but when found it has no significance, as we have seen, and it can
be ascertained more easily and about as accurately by the thermometer and meter
readings, given some knowledge of the quality of the steam in respect to superheating.
For ascertaining this latter fact only, occasional quantitive observations of the
vapor or liquid used per hour may be useful.
Referring now to the plate boiler, the use of which is very desirable on account
H

page_text: of the expense and difficulty of securing the very small and thin tubes desirable, and
-ince it enables a uniform interspace to be secured, the general construction in a
simple form is outlined in Figures 37 to 39.
The boiler is preferably formed of a series of sections U, each section consisting
of a pair of plates indented or corrugated so as to form one or more continuous
passages u between them extending in a serpentine path downward from top to
bottom through the section, each one of these sections U connecting at the top
through one or more pipes 47 with the circulating fluid pipe, or the exhaust steam
pipe in secondary step series boilers, and at the bottom by one or more pipes 48
with pipe V. These sections are nested closely together, as shown in Figure 39,
though this arrangement may be varied, and are spaced preferably from one-eighth
10 one-quarter of an inch between centers, though this also may be varied considerably,
and in such a manner as to leave irregular passageways of very limited width
between them, through which passageways the working substance passes from
the bottom to the top of the boiler, the working substance being fed in at the
bottom of the boiler through the feed pipe 20 and the vapor passing out from
the top of the boiler through the steam pipe O. In boilers of this type having
little or no steam space it is expedient that the steam pipe should be
exceptionally large, as shown in the drawings, in order to contain a little store
of vapor for two or three strokes as well as to avoid wire drawing. At the
bottom of the boiler it is preferable to leave plenty of space to accommodate
the pipe or pipes V', as it is desirable to have this room for the condensed
fluid to distribute itself equally, and for the same reason it is desirable to have
some space about the pipe or pipes V at the top of the boiler, though it need
only be large enough to give an even draft of steam from all over the top of
the boiler, and the domed form shown in Figure 29 is desirable for this purpose.
To form the construction shown in Figures 37 to 40 I take thin copper or other
metallic plates and corrugate them in such a manner that, when the plates are
assembled face to face into the sections above described consisting of two faced
plates, the corrugations form from one to ten continuous serpentine tubular
passages u extending from the top pipe or pipes V to the bottom pipe or pipes V1
previously described. The plates forming a section are preferably brazed together
only at the edges and until these sections are assembled together into a boiler and
subjected to the excess of external or collapsing pressure, which naturally obtains
under their conditions of use, the formation of the tubes may be quite imperfect,
so that the interior space is rather a single open chamber than a series of tubes,
but the slightest excess of external pressure brings the flat surfaces into quite close
contact, as shown on a much enlarged scale in Fig. 40, with the result that the
serpentine tubes are practically tight against any slight difference of pressure, and
all or nearly all the exhaust is compelled to follow the much elongated path
indicated in Figure 37. It does not matter if a little of the exhaust should fail to
do so, but pass across from tube to tube through some slight aperture caused by
the plates not being in perfect contact. As there is only a very small difference of
pressure between adjacent tubes, and light plates are very forcibly compressed by a
considerable excess of external pressure, perhaps 100 to 200 lbs. per sq. in., this can
rarely happen in any degree.
In
Although an excess of external pressure is the usual rule, however, it may and
does happen in special cases that an excess of internal pressure is convenient.
this case the interior serpentine circulation may be a little less perfect, since the
relative pressures tend to destroy instead of perfect the metallic surface contacts
which form the tubes, but to the end that there may be no practical difference
between the two cases, I preferably provide by spacing tits or otherwise that the
adjacent sections may be in contact at frequent points, and by assembling the boiler
under a moderate initial pressure which is maintained within the boiler shell by
suitable end plates or spaces, I arrange that no plate can move injuriously from or
into contact with its neighbors under either external or internal excess of pressure.
The position of these spacing tits is indifferent.

page_text: It is important to provide more or less of a flat-bearing surface where the two
plates of a section come in contact, as shown in Figure 40, and not to make
these bearings mere rounded knuckle edges, as, in the latter case, external
pressure tends to cause these surfaces to slip past each other, if they are in
the least degree out of position, and the section is collapsible by much less
pressure.
In Figure 41 is shown a preferred construction embodying an important
practical feature The form of corrugated plate shown in Fig. 37 is weak in
this, that the straight cylindrical tubes at top and bottom of the section, which in
effect become semi-circular arches when subjected to pressure, have no abutment
along the outer edge, except the very slight resistance of the brazed edge to being
sprung outward from a straight line. Such a contraction, therefore, although
functionally perfect, is mechanically defective. To obviate this, and at the same
time secure further advantages, I prefer in all cases to form the tubes of a
series of intersecting hemispheres or spheroids indented in the plate instead of
forming them of semi-cylinders, as shown in Figure 37. The sphere is the
strongest form in which sheet metal can be disposed of to resist pressure, and
the strength of the outer tube is increased from ten to twenty fold by this
simple change. Moreover, the tube thus formed, having an irregular cross section
alternately contracted and expanded, produces a sort of whirling action in the
fluids on both sides of it which I have found to increase very largely the rate of
heat transfer under thermally similar conditions. For this reason, as well as for
the sake of greater strength, I prefer to form all the tubes of these intersecting
spheres or spheroids.
As even then the outer tubes are weaker I extend this principle, for the outer
tubes at least, and for all the tubes, if desired, by staggering the spheres or
spheroids in the manner shown in Fig. 42, so as to give a continuous zig-zag
form to the tubes u with the center of a sphere or spheroid at each angle. This
still further improves the functional action of the tubes as heating surfaces and
gives an extraordinary strength and stiffness to the tubes, so that the outer ones
are as strong as any others, and all will resist some thousands of pounds per
square inch pressure although formed of quite thin copper, especially if the size
of the spheres or spheroids is not more than one quarter inch diameter with
connecting intersections of about one eight inch diameter, which
proportions which at the present time I deem most suitable, though further
experience may modify this view by showing that larger or smaller dimensions will
give still better results.
are the
It will be understood that the constructions illustrated are only some of the
preferred forms of plate boilers which may embody the invention, considered
broadly. Thus, instead of forming the passages by indentations or corrugations, a
boiler may be made of parallel plates held apart by indentations or corrugations,
or otherwise, and the spaces between the plates form the passages for the heating
fluid and fluid to be heated, alternate spaces connecting with the supply spaces for
the respective fluids.
It is obvious that this construction is equally well-adapted as a pressure
generator, condenser, heater, or cooler, and that it is functionally indifferent
which of the two fluids passes through the sections and which through the
spaces between the sections, although in most constructions it will be better
mechanically that the hot fluid should go through the open spaces between the
sections.
Having now particularly described and ascertained the nature of the said
invention, and in what manner the same is to be performed, as communicated to
me from abroad, I declare that what is claimed is :-
1. In a thermodynamic process in which a circulating fluid passes from a supply
or source of heat to a pressure generator thermally dissociated from said supply or
source of heat and containing the working substance, and the working substance is

page_text: heated by the surrender of heat thereto from the circulating fluid, the use,
substantially as described, of some or all of adjuncts A to F hereinbefore
described.
2. The process defined by Claim 1 above and employing some or all of
adjuncts A to F, but with the circulating fluid returned from the pressure
generator to the supply or source of beat, substantially as described.
3. The process defined by Claim 1 above and employing some
or all of
adjuncts A to F, but with the vapor of the working substance exhausted into a
condenser after use and cooled by the circulating fluid after the latter is
discharged from the pressure generator and suitably cooled, substantially as
described.
4. The process defined by Claim 1 above with the additional steps of applying
the working substance in an expansion engine, applying the exhaust from said
engine to heating a second working substance, applying said second working
substance in a second expansion engine, and so on, if desired, for other successive
working substances and engines, substantially as described.
5. The process defined by Claim 4 above, but applying the exhaust from the
successive engines to heating the hotter and colder parts of the working substances
successively by passing it downward through the working substance in the
successive pressure generators in uniformly distributed and closely spaced
passages, substantially as described.
6. The process which consists in generating or increasing vapor pressure in a
working substance in any suitable manner, applying said working substance in an
expansion engine, applying the exhaust from said engine to heating a second
working substance by passing it downward through the working substance in
uniformly distributed and closely spaced passages having thin heat transmitting
walls, and so on, if desired, for other successive working substances and engines,
substantially as described.
7. The series engine process herein before described which consists in passing a
circulating fluid through a series of pressure generators and applying it to heating
working substances in said pressure generators, applying said working substances
in expansion engines, and applying the circulating fluid to condensing the working
substances exhausted from some or all of the successive engines, substantially as
described.
8. The process defined by Claim 7 above, but passing the circulating fluid
through a closed circuit so as to repeat the operation, heating the circulating fluid
before entering the hot circuit and cooling it after leaving the hot circuit,
substantially as described.
9. The process defined by Claim 7 above, but employing a circulating fluid
partly liquid and partly gaseous, and repeating the circuit with the liquid portion
of the circulating fluid, heating said liquid portion before entering the hot circuit
and cooling it after leaving the hot circuit, substantially as described.
10. The process defined by Claim 7 above, but passing fuel through the
condensers and applying it to cooling the working substances therein and then
burning the fuel in a heater and employing the gases of combustion as circulating
fluid in the pressure generators, substantially as described.
11. The process defined by Claim 10 above, but using the fuel in the condenser.
in conjunction with a circulating fluid, heating the circulating fluid by burning the
fuel, then passing the gases of combustion and circulating fluid through the
pressure generators together, and repeating the operation with the circulating
fluid in conjunction with another supply of fuel, cooling the circulating fluid after
leaving the hot circuit, substantially as described.
12. The process defined by Claim 7 above, but using the circulating fluid after it
has been heated by condensing the working substances in the cold circuit as hot
circulating fluid for other series working at lower maximum temperatures, and
cooling the circulating fluid after leaving the hot circuit of the different series,
substantially as described.

page_text: 13. The process defined by Claim 7 above, but applying the circulating fluid after
its use for heating the working substances in the pressure generators to heating
another circulating fluid and applying the second circulating fluid in a series of
pressure generators working at a lower maximum temperature than the first-
mentioned series, substantially as described.
14. The process defined by Claim 7 above, but carrying the circulating fluid
through or past one or more of the condensers for the working substances
without applying it to condensing the working substance therein, substantially
as described.
15. The process defined by Claim 7 above, but applying the circulating fluid
to condensing the working substances from only a part of the successive engines
and exhausting the other engines into the circulating fluid, substantially as
described.
16. The process defined by Claim 7 above, but employing cold interval engines,
hot interval engines and heating engines, or any of these, as hereinbefore
described.
17. The method of increasing the efficiency of engine systems employing a
circulating fluid for heating and condensing the working substances, which consists
in applying the fuel as part of the circulating fluid in condensing the working
substances and then burning the heated fuel in the heater for heating the
circulating fluid, substantially as described.
18. The method of increasing the efficiency of engine systems employing a
circulating fluid for heating and condensing the working substances for a series of
engines, which consists in cutting out the circulating fluid from one or more of the
condensers and substituting another condensing material, substantially
described.
as
19. The method of utilizing the thermal interval between the temperature of
combustion and maximum temperature of the circulating fluid in thermodynamic
systems employing a circulating fluid for heating the working substance, which
consists in heating the circulating fluid by the waste heat from gas or other engines
working in said interval, substantially as described.
20. The method of generating or increasing vapor pressure by heating a
working substance, or of transferring heat from one fluid to another for any
purpose, which consists in passing the hot fluid downward through the cold
fluid and preventing downward circulation of the cold fluid, substantially as
described.
21. In the process defined by Claim 20 above, the use of thin heat-
transmitting walls as defined, for reducing the thermal head, substantially as
described.
22. In transferring heat from one fluid to another, the use of passages
alternately expanded and contracted in cross section through which the fluids
are passed, to produce a whirling movement of the fluids, substantially as
described.
23. The process of condensing or cooling a vapor, which consists in passing
the vapor through a series of passages immersed in a cooling liquid and
circulating said liquid by continuously withdrawing liquid from the top and
injecting it upward at different points at the bottom of the liquid with sufficient
force to maintain a constant agitation of the surface of the cooling liquid,
substantially as described.
24. In a system employing a circulating fluid as described, the combination with
a heater, a pressure generator thermally dissociated from the heater for applying
the circulating fluid to heating the working substance, and connections from the
heater to the pressure generator for the circulating fluid, of devices for carrying
out substantially as herein described some or all of adjuncts A to F hereinbefore
described.
25. In a system employing a circulating fluid as described, the combination with
a heater, pressure generator thermally dissociated from the heater for applying

page_text: the circulating fluid to heating the working substance, and connections from the
beater to the pressure generator and return to heater for the circulating fluid, of
devices for carrying out substantially as herein described some or all of adjuncts A
to F hereinbefore described.
26. In an engine system employing a circulating fluid as described, the
combination with a heater, a pressure generator thermally dissociated from the
heater for applying a circulating fluid to heating the working substance, and
connections from the heater to the pressure generator for the circulating fluid, of
devices for carrying out substantially as herein described some or all of adjuncts A
to F hereinbefore described, an expansion engine operated by said working
substance, one or more secondary pressure generators and expansion engines and
connections for the exhaust from the expansion engines to the next pressure
generator, substantially as described.
27. The combination with a series of expansion engines and pressure generators
and condensers therefor provided with passages for applying a circulating fluid to
heating and condensing the working substances, of connections between said
passages through the series of pressure generators and some or all of the condensers
for the circulating fluid, substantially as described.
28. An apparatus such as defined by Claim 27 above, but employing a heater
and a cooler, and connections between the circulating fluid passages and the heater
and cooler, substantially as described.
29. An apparatus such as defined by Claim 27 above, in combination with
devices for regulating either or both the maximum and minimum temperature of
the circulating fluid in the hot circuit, substantially as described.
30. An apparatus such as defined by Claim 29 above, but with the pressure
generators and condensers provided with uniformly distributed and closely spaced
passages, through which passages the hotter fluid is passed downward through the
colder fluid, substantially as described.
31. An apparatus for carrying out the process defined by Claim 1 above,
substantially as described in connection with Figures 17 to 28.
32. A pressure generator or condenser substantially as described in connection
with Figures 21 to 23.
33. An apparatus for carrying out the step series engine process above described,
substantially as described in connection with Figure 29.
34. An apparatus for carrying out the series engine process above described,
substantially as described in connection with Figure 30.
35. An apparatus for carrying out the process defined by Claim 13 above,
including two or more series of expansion engines working at different maximum
temperatures, and a transmitter whereby the circulating fluid of the hot series in
passing from the hot to the cold circuit heats and is cooled by the circulating fluid
of the cold scries in passing from the cold to the hot circuit, substantially as
described in connection with Figure 31.
36. A pressure generator or condenser for use in carrying out the series engine
process above described, substantially as described in connection with Figures 32
to 35.
37. In a system employing a series of pressure generators or condensers having
passages for applying a circulating fluid to heating or condensing working
substances, the combination with the circulating fluid connections between the
passages of the different pressure generators or condensers, of by-passes for
cutting out one or more of said pressure generators or condensers, substantially as
described.
a
38. In a system employing a series of condensers having passages for applying
circulating fluid to cooling working substances, the combination with the circulating
fluid connections between the passages of the different condensers, of by-passes
for cutting out the circulating fluid from one or more of said condensers, and
connections for supplying another cooling medium to said condensers, substantially
as described.

page_text: 39. A. boiler or other heat transferring apparatus having uniformly distributed
and closely spaced passages for the heating fluid extending downward through the
fluid to be heated, substantially as described.
40. A boiler or other heat transferring apparatus such as defined by Claim 39,
in which the passages are provided with thin heat transmitting walls to reduce the
thermal head, substantially as described.
41. A boiler or other heat transferring apparatus, having its interior space
divided by a series of parallel plates extending transversely to the boiler casing
and placed side by side with spaces between them, alternate spaces connecting
respectively with the heating fluid and fluid to be heated, substantially as
described.
42. A boiler or other heat transferring apparatus such as defined by Claim 41,
in which the plates are indented or corrugated to form passages between them,
substantially as described.
43. A boiler or other heat transferring apparatus such as defined by Claim 41,
in which the plates are secured together in pairs to form sections with passages
between them formed by outward indentations or corrugations in the plates,
substantially as described.
44. A boiler or other heat transferring apparatus such as defined by Claim 43,
in which the passages are formed by intersecting spherical or spheroidal indentations
in the plates, substantially as described.
45. A boiler or other heat transferring apparatus such as defined by Claim 44,
in which the spherical or spheroidal indentations are staggered to form zigzag
passages, substantially as described.
46. A boiler or other heat transferring apparatus such as defined by Claim 43,
in which the sections are arranged vertically and the passages within and between
the sections connect with separate passageways at top and bottom of the boiler, the
heating fluid passing downward and the fluid to be heated upward through the
respective sets of passages, substantially as described.
47. A boiler or other heat transferring apparatus substantially as described in
connection with Figures 37 to 42.
Dated this 19th day of November 1895.
NEWTON & SON,
Agents for the Applicant.