Improvements in Refrigerating Apparatus.
Year: 1899

page_text: Improvements in Refrigerating Apparatus.
A communication to me from H GEPPERT, of Kaiserstrasse 65, Carlsruhe, Grand-
Duchy of Baden, in the Empire of Germany, Engineer.
I, EDMUND EDWARDS, of the Firm of Edwards, and Co., Chartered Patent Agents
and Engineers, of 65 & 66, Chancery Lane, in the County of Middlesex, do
hereby declare the nature of this invention to be as follows:-
The present invention relates to an improved continuous absorption refriger-
ating apparatus, which essentially differs from apparatus of the kind heretofore
made, in that unlike such apparatus the whole of the chambers of the appara-
tus communicate with each other and consequently are under the same pressure,
and that the apparatus, in addition to vaporizable and absorption fluids and their
vapours, is filled with air or other gas or vapour (superheated steam) or a mixture
of gases or vapours under suitable pressure.
In order to clearly understand the operation of the apparatus, the following
general conditions should be first borne in mind.
Any liquid evaporates in a chamber filled. with gaseous fluid, (for example,
water in the atmosphere), even at a lower temperature than the boiling point and
accordingly at a lower tension that the pressure upon the liquid amounts to.
The vapour mixes with the gaseous fluid by diffusion and this mixture is
richest in vapour on the surface of the liquid, and is always less rich in it the
greater the distance from such surface and the lower the temperature of the liquid
The pressure of different mixtures is constant, and is constituted, according to
physical laws, both of the pressure of the vapour and of the gas together.
If we take different open vessels filled with a liquid at different temperatures
close to. chambers filled with gas, mixtures will be formed containing different
proportions of liquid and gas, the total pressure of which is always the same.
Take for example water as the liquid, and the atmosphere for the gas-filled
chamber, the total pressure will be equal to 760 m.m. of mercury, if water at 20°
Celsius equalling 17 m.m. (the proportion of vapour pressure) + 748 m.m. (the pro-
portion of air pressure) = 760 m.m. If of water at 90° Celsius equalling 525 m.m.
(proportion of vapour pressure) + 235 m.m. (proportion of air pressure
760.m.m.
If of water at 100° equalling 760 m.m. (proportion of vapour pressure) + 0 m.m.
(proportion of air pressure) 760 in.m.,
the proportion of air pressure being in this
Case = 0, and the proportion of vapour or steam pressure 760 m.m., when the water
boils and drives out the air.
If the vessels are arranged close to each other in a vacuum, the water is very
quickly distilled over from the hot to the cold .vessel.
In gas-filled chambers, this distribution also goes on but slowly by means of
diffusion.

page_text: The quantity of vapour to be diffused through a layer of gas in a certain time
is. the greater, the greater the surface of the liquid to be evaporated; and the
greater the cross section and the thinuer the layer of gas.
A refrigerating diffusion and absorption machine acting on the principle de-
scribed is theoretically constructed as follows:-
The evaporating vessel (refrigerator) contains the vaporizable liquid,..and its
bottom is on the lower side covered with a suitable porous material which is also
brought up through a central opening having a pipe on its upper side the
open top of which is above the level of the liquid, the porous material hanging
over its top and dipping into the liquid, which is sucked up and saturates the
whole of the porous material which has a large surface. The absorption chamber
is arranged below, the surface of the liquid in it being a very short distance below
the saturated material described.
Saltwater or brine circulates through tubes passing through the upper
(evaporating) vessel, and cold water passes through similar tubes in the lower
absorption chamber.
The vaporizable fluid is evaporated and diffused through the gaseous fluid which
fills the upper vessel and the lower absorption chamber, and is absorbed in the
absorption fluid contained in the latter. This fluid passes round a horizontal
partition in the lower chamber and becomes saturated with the vapour of the
vaporized liquid, the saturated fluid then passing out through a pipe at the
bottom of the chamber to a heating chamber in which the vaporized liquid is
expelled from it by heating. The liquid then passes through a pipe in the upper
part of the heater, which pipe passes in the form of a coil through a vessel where
it is cooled by cold water, and thence to the upper part of the lower or absorption
chamber, a continuous circulation being kept up through the pipe.
The vapour disengaged in the heating vessel passes through a pipe into a
condensing coil where it is condensed by cold water and the liquid then passes
back through a pipe to the upper vessel, and the cycle of operations recommences
and continues without intermission.
This being the principle upon which the apparatus is constructed and works,
an arrangement will now be described in detail, in which ammonia and water
are used.
The apparatus is filled with ammonia, water, and a gas or vapour under a
pressure of about 15 atmospheres.
The pressure of the liquid ammonia amounts in the vaporizer to 25 atmospheres
in the condenser to 08 atmospheres, as in ordinary ammonia machines. In the
absorbing chamber the pressure is a little less than 25 atmospheres. In the
heater the fluid to be boiled has a pressure of 15 atmospheres, considerably more
than in the ordinary ammonia machines, in which the heater and the condenser
are under the samo pressure.
=
The total pressure in all parts of the apparatus is 15 atmospheres, and is con-
stituted according to the general conditions already explained. That is to say,
in the vaporizer 2.5 atmospheres (the proportion of vapour pressure) + 12.5 atmo-
spheres (proportion of gas pressure) 15 atmospheres. In the condenser 8 atmospheres
(proportion of vapour pressure) + 7 atmospheres (proportion of gas pressure) = 15
atmospheres. In the heater (or boiler) 15 atmospheres (proportion of vapour
pressure) +0 atmospheres (proportion of gas pressure) 15 atmospheres. Shortly,"
at each point of the apparatus the total pressure amounts to 14. atmospheres, which is
made up of the proportion of vapour pressure plus the added proportion of gas
pressure.
=
The vapour (or steam) in. the heater (or boiler) has, on account of the boiling,
a tension of 15 atmospheres, and it therefore expels the gas (or gaseous fluid),
and flows on to the condenser, where it is for the most part condensed and brought
to a pressure of 8 atmospheres, at which pressure it can only diffuse itself through
the gas in the connecting pipe to the vaporizer. As this pipe is narrow and long,
only a small volume of vapour can be diffused, and the calorific effect of the

page_text: apparatus is but little hindered. The liquid ammonia flows by its own gravity
to the vaporizer.
-
The vapour present in the apparatus serves also as an automatic regulator.
In the vaporizer and the absorber the action of the vapour also takes, place by
diffusion, but here the vaporizing and absorbing surfaces are so large and the
distance between them so small, that large quantities of vapour pass over and an
energetic production of cold is brought about.
In these arrangements both in the condenser and the vaporizer different tem-
peratures may exist simultaneously at different points, which can be advantage-
ously used for the useful calorific effect of the apparatus.
The liquids in the apparatus can circulate freely, as already explained, as they
are everywhere under the same pressure. In consequence the throttle valves and
pumps necessary in ordinary, absorption machines,.. between the condenser and
vaporizer, and between the absorber and the heater, are not required.
In the improved diffusion-absorption refrigerating apparatus, all the different
known vaporizable liquids may be used, such as ammonia, chloro-methyl, methyl
ether chlorethyl, ethylether, petroleum ether, and the like; and as absorption
fluid, water, different alcohols, and the like.
The vapour pressure in the apparatus depends upon the volatility of the
vaporizable liquid, and is in general the greater, the more volatile the liquid is.
The proportions of the apparatus are best, when adapted to the use of volatile
liquids, the boiling points of which are between +20° and +50° Celsius below
atmospheric pressure, as by this means the ruling total pressure can be made
about 1 atmosphere.
".
Taking the construction already described as illustrating the principle, a
practical working apparatus may be made as follows:-The vaporizing chamber
has a bottom formed of porous plates put together in zigzag form; so as to form a
series of vertical recesses open below. In these recesses turn the upper part
of revolving discs fixed upon a horizontal shaft passing through the apparatus
below, whilst the lower parts of the discs revolve in the absorption chamber
below.
These discs serve to diffuse the vaporized liquid, which passes through the
porous plate forming the bottom of the upper chamber, the discs always present-
ing a fresh surface covered with the absorption fluid in which they revolve.
The circulation of the absorption fluid from the lower chamber to the heater
and from the heater through a pipe and condensing coil back to the "chamber,
takes place by means of the difference in specific gravity of the fluid in the
heater and the chamber respectively assisted by a fan or screw upon the prolonged
end of the-revolving shaft driving the discs, the fan being in an enlargement of
the pipe from the heater to the upper part of the absorption chambor. The fan
is not essential, and is not intended to act as a pump between the absorber and
the heater. The remainder of the apparatus and its method of working is similar
to that already first described.
•
In another somewhat modified form of the apparatus, the vaporizer consists
essentially of transverse tubes, covered with porous material, and through which
salt water or brine circulates. The condensed liquid flowing from the upper
cold water condenser falls through a sieve or perforated plate, upon the tubes.
A revolving fan below draws the vapour between the tubes, the liquid becoming
vaporized cooling the tubes and the different vapours being mixed by diffusion,.
and passing into the absorbing chamber, where the vapour is absorbed. The
absorber consists, substantially, in this case, of transverse tubes covered with
porous material, through which cold water circulates. A smail pump raises the
absorbing fluid and distributes it through a screen or sieve upon the tubes, which
are thus kept saturated.
...This pump does not serve as a pressure pump such as is used in ordinary
absorption machines between the absorber and heater. It is not of essential

page_text: importance, any more than the fan, which simply serves to mechanically acccler-
ate the diffusion process between the vaporizer and the absorber.
The heater may be heated in any suitable way; as for instance by means of
lieating coils passing through it.
n
1000
A communication to me from H GEPPERT, of Kaiserstrasse 65, Carlsruhe, Grand-
Duchy of Baden, in the Empire of Germany, Engineer.
I, EDMUND EDWARDS, of the Firm of Edwards and Co., Chartered Patent Agents
and Engineers, of 65 & 66, Chancery Lane, in the County of Middlesex, 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, and accompanying drawings, that is to say:―
In the continuously acting absorption refrigerating apparatus hitherto, known,
the process of producing cold is performed by evaporating a liquid, absorbing
the vapours by a suitable absorption liquid, expelling the absorbed vapours from
the liquid by boiling heat, condensing the vapour expelled in the boiler by cooling
the same and returning the condensed liquid from the condenser into the evapor-
ating vessel. This process goes on in an apparatus containing nothing but the
evaporating and absorption fluids and vapours.
The condenser and the vaporizer in such an apparatus show different pressures
corresponding to the different temperatures. The pressure in the boiler is ap-
proximately equal to that in the condenser, which is at one end in direct con-
nection with the boiler, and the pressure in the absorber is approximately equal
to that in the vaporizer which is in direct connection with the absorber.
In order to feed the absorption liquid into the boiler a pressure pump has to
be used, to make up the difference between the pressures in the absorber and in
the boiler, and in order to lead the condensed vapours to the vaporizer and the
absorption liquid from the boiler into the absorber, reduction valves are inter-
posed between the condenser and the vaporizer and between the boiler and the.
absorber.
The present invention is a modification of the above process, and consists in
introducing some gas or vapour, preferably air, other than the vapours of the
evaporating and absorption fluids, into the vaporizer and absorber, and eventually
into the condenser under a suitable pressure, and raising by its means the pressure
in the vaporizer and absorber, and eventually in the condenser, and equalizing
approximately the pressure in the whole apparatus.
By this means the raising and lowering of the pressures, and the accompanying
inconveniences in the continuous process can be dispensed with or materially
diminished. At the same time the process is changed in so far as the evaporated
gas does not move as an undivided body through the conduits or passages, but
there is a diffusion of these vapours through the admixed gas or vapour, which
is itself neither condensed nor absorbed, nor appreciably moved from the con-
denser into the vaporizer nor vice versa.
The admixture of air and raising of the pressure in the vaporizer does not
prevent the evaporation, according to well-known principles of physical science.

page_text: In a room filled with gas any liquid evaporates without being raised to boiling
heat and pressure. The vapour arising mixes with the gas by diffusion, and
this mixture contains on the surface of the liquid the greatest percentage of
vapour; this percentage of vapour gradually decreases with the distance from
the surface of the liquid and with the decrease of the temperature of the liquid.
Supposing several open vessels of different temperatures filled with a liquid-
for instance, with water and set up close to each other in a room filled with
gas--for instance in the atmosphere-the pressure of 760 mm. mercury exists
everywhere; according to the law of Dalton this pressure is composed above the
water at a temperature of +20° C. of 17 min. partial vapour pressure +743 min
partial air pressure 760 mm:; above water of +90° C..the pressure is composed of
525 mm. partial vapour pressure, + 235 mm. partial air pressure
760 mm.;
above water of 100° C. the pressure is composed of 760 mm. partial vapour
pressure +0 mm. partial air pressure = 760 mm.
=
=
The partial air pressure is here equal to 0 and the partial vapour pressure
equal to 760 mm., that is to say, the water is boiling and displaces the air entirely.
Should these vessels stand close by each other in a vacuum, on account of the
great difference of the different vapour pressures the water would distil.over very
rapidly from the warmer to the cooler vessels.
This distillation takes place in a gas-filled chamber also, but much more slowly,
by diffusion.
The quantity of vapour which is diffused through a layer of gas in a given unit
of time is proportional to the area of the surface of the evaporating liquid, and
in inverse proportion to the thickness of the layer.
The above explained principle constitutes the base of the present invention,
according to which a liquid is evaporated in an atmosphere containing another
gas than that generated by the evaporation, and the generated vapours pass on
by diffusion to an absorber.
It is apparent that the new process may be carried out in different forms of
apparatus. In the accompanying drawing are shown by way of example three
different modifications of such apparatus.
Figure 1 is a diagrammatic section of such a theoretical apparatus.
Figures 2 and 3 are corresponding sections of two modified forms of this
apparatus.
Referring to Figure 1, the vaporizer a contains the evaporating liquid b, and
its bottom is lined underneath with a porous substance & which extends up
through the opening e and is immersed in the evaporating liquid b. This porous
substance becomes saturated by sucking up the liquid b, and thereby possesses
a large evaporating surface. At a short distance below is the surface of the
absorption liquid g which is contained in the absorption chamber or absorber f.
Salt water (brine) passes through the pipes h in the vaporizer, and cold
water through the pipes in the usual way. The liquid 6 is evaporated and
diffused in the direction of the arrows z through the gas, which fills the vaporizer a
and the absorber f, and is absorbed by the absorption liquid. g. This liquid,
containing the vapours of the evaporating liquid b, runs tarough the absorber f
in the direction of the arrows u and through the pipe into the heater or
boiler where the vapours contained in the liquid are expelled by boiling. The
absorption liquid then runs through the pipe m which is refrigerated by cold
water in a cooling vessel as shown, back into the absorber f.
This circulation is produced by the fact that the liquid which is heated and
boiling in through the medium of the heater is specifically lighter than at
f, and stands, therefore, in higher than it does in f, and circulates continually
through m towards f.
The vapours are discharged from the boiler through the pipe n into the con-
densor o, where they are condensed by the cooling water, and run through the
pipe p into the vaporizer a, and the circulation is then commenced afresh.

page_text: Supposing that the apparatus is to be worked with ammonia, the working is
as follows:-
I
تا
The apparatus is filled with ammonia and water, and air at a pressure of—for
instance 15 atmospheres. The vapour-pressure of the liquefied ammonia in the
vaporizer amounts, at the temperature subsisting in the vaporizer, 'to; for in-
stance, 25 atmospheres, in the condenser o on the average to 8 atmospheres.
The vapour pressure in the absorber is a little under 25 atmospheres, and 'the
boiling liquid in the boiler b' produces a vapour pressure of 15 atmosphères.
According to the previous explanations the pressure is composed, in the vaporizer,
of 25 atmospheres partial vapour pressure + 125 partial au pressure = 15 atino-
spheres; in the condenser, of 8 atmospheres partial vapour pressure +7 stinospheres
partial air pressure = 16 atmosplieres; in the boiler, of 15 atinospheres partial vapour-
pressure 0 atmospheres partial air pressure = 5 atmospheres.
Consequently, there is at every point in the apparatus a 'total' pressure of lo
atmospheres. If any air should have been introduced into the boiler the
vapour in the boiler expels it on account of its boiling pressure. The vapour
itself is discharged through the pipe into the condenser o, is condensed and
brought to a partial pressure of 8 atmosphores, which permits the diffusion only
through admixed 'air in the pipe towards the vaporizer a. The˜pipe 7 being,
however, narrow and long, only a very moderate quantity of vapour will diffuse
over uncondensed; which will only slightly diminish -the caloric effect of the
apparatus.
The liquefied ammonia runs through the pipe p to u.
The movements of the vapours in the vaporizer a and absorber f take place by
molecular diffusion only, and not by bodily mechanical dislocation: The evapor-
ating and absorbing surfaces are so extensive; and the distance of both so short,.
that great quantities of vapour diffuse over, and an energétic refrigeration is
obtained.
212
It is clearly shown by these explanations that in different points of the condenser
as well as in the vaporizer different temperatures can exist, which can favourably
be utilized for the caloric useful effect of the apparatus by running the salt water
through the pipes and the cooling water through the condenser by counter-
current. The liquids of the apparatus can easily perform the circulation men-
tioned on account of the same pressure approximately existing through all the
apparatus. The throttle valves, forcing pump, injector, and the like, between
the condenser and the vaporizer, as well as 'between the absorber and the boiler
as used in the ordinary. absorption machines are, therefore, omitted.
Referring to Figure 2 (which shows one form of the apparatus), a is the
vaporizer (refrigerator) the bottom d of which is composea of porous plates laid
in a zigzag manner. In the spaces between these zigzags are arranged discs q
which are mounted upon a revolving axis r and whose lower parts dip into the
absorption liquid g. From this porous bottom d, which is impregnated with the
evaporating liquid b, the vapours diffuse towards the discs g, which are moistened
by the absorption liquid g, and which are continually presenting new surfaces as
they revolve.
The circulation of the absorption liquid g from f through towards l, and
from through m back again to f is accelerated by the fan or screw s on the axis.r
The other parts of the machine are the same as in Figure 1, and are designated
by the same reference letters.
Referring to Figure 3, (which shows another modified form of the apparatus)
the vaporizer (refrigerator) a consists of the pipes h, which are covered with a
suitable porous material, and through which salt water, is circulated.
The evaporating liquid which comes from the condenser is..distributed over
the pipes by the rose or perforated plate. The fan u blows, the gas which the
apparatus contains through the spaces in between the pipes h, whereby the
evaporating liquid evaporates; cooling the pipes h
As indicated by the arrows, the mixture of gases passes through the channels.

page_text: or passages into the absorber where the vapours, are absorbed, whilst the air
is returned directly between the pipes h.
The absorber consists of the pipes i, which are covered with the porous
material, and in which circulates the cooling water. A small pump w supplies the
rose or perforated plate y which sprinkles the pipes i of the absorber with the
absorption liquid g.
The mode of operation of the apparatus, and the reference lotters, are the same
as shown in Figure 1.
The pipes marked in Figures 2 and 3 are heating coils to heat the boiler /
and perform the same function as the heater in Figure 1.
It is understood that in carrying out the described process all supplementary
devices used in machines of the described nature are to be applied in their proper
place, though not shown in this specification.
In the above-described. example the total pressure was given at about 15 atmos-
pheres, but this pressure can be varied between wide limits, but it is not desirable
to go under 8 atmospheres.
The pressure in the boiler may be somewhat higher than in the evaporator,
in order to keep up the circulation and overcome the friction in the conduits.
As it is desirable to raise the pressure in the vaporizer sufficiently to entirely
dispense with throttle valves and pressure pumps and the like, it is apparent
that a great advantage also may be obtained, though by keeping the pressure
under that limit, less power is required for the pump and less wear and tear of
the pump and valves, and a better operation of the same secured.
Ail the well-known liquids as ammonia, chloride of methylene, methyl ether,
chloride of ethylene, sulphuric ether, carbonic disulphide, first essence of petro-
leum, and the like, can be utilized in the new process as evaporating liquids, and
water, different alcohols, hydrocarburets, and the like, as absorption liquids..
The additional gas pressure to be given in the apparatus can be varied within
wide limits, and depends upon the vapour pressure of the evaporating liquid,
and is in general the greater, the more volatile this liquid is, that is to say, the
greater the vapour-pressure of this liquid is.
The construction of the apparatus is most favourable for the utilization of
evaporating liquids whose boiling points at the atmospheric pressure = 760 mm.
mercury are between +10° and +50° C, as the total pressure in the apparatus can be
raised thereby to about one atmosphere 760 mm. mercury.
=
A great advantage in the construction of the apparatus is thus obtained, inas-
much as the vessels need not be constructed to sustain external pressure.
This raising of the pressure is equally advantageous with regard to pumps,
as no air pump need be applied.
Having now particularly described and ascertained the nature of the said in-
vention, and in what manner the same is to be performed, I declare that what
I claim is:-
1. In the process of producing cold by evaporating a liquid, absorbing the
produced vapour by an absorption liquid, expelling the vapour from the latter
by heat, condensing the expelled vapour by refrigeration, and returning it into
the vaporizer, the method of causing the evaporation and absorption to go on in
a vaporizer and an absorber containing a quantity of gas or vapour other than
the vapours of the evaporating and absorption liquids, whereby the pressure in
the vaporizer and absorber is raised and made approximately equal to the
pressures existing in the condenser and boiler, substantially as described.
2. In the described process of producing cold, the method of causing the con-
densation of the vapour expelled by heat to go on in a condenser containing a
quantity of gas or vapour other than that to be condensed, whereby the pressure
in the condenser is raised and the diffusion of such vapours and the outflow of
the condensed vapours into the vaporizer is made possible, substantially as
described.

page_text: 3. In the described process of producing cold, the method of circulating the
liquids and vapours through open passages or conduits from the absorber to the
boiler and from the boiler to the vaporizer and absorber, substantially as
described.
4. In the described process of producing cold by evaporation in an atmosphere
in which a non-evaporating and non-absorbing gas is present, the method of
causing the evaporated gas to pass by diffusion from the surface of the vaporizer
through a thin layer of the said atmosphere to the opposite surface of 'the absorb-
ing liquid, substantially as described.
11
EDWARDS AND CO.,
Chartered Patent Agents,
65 and 66, Chancery Lane, London, Agents for the Applicant.