Improvements in Apparatus for Refrigerating and Liquefying Air or other Gases.
Year: 1898

page_text: PROVISIONAL SPECIFICATION.
Improvements in Apparatus for Refrigerating and Liquefying Air or
other Gases.
I, EDGAR CHARLES THRUPP, Civil Engineer, of Southdene, Ashley Park Road,
Walton-on-Thames, Surrey, do hereby declare the nature of this invention to
be as follows:-
In refrigerating apparatus depending on the compression of air, cooling by
water &c., and subsequently by expansion in a cylinder against a piston doing
mechanical work, there are several practical difficulties which militate against
the cooling of the air through very large ranges of temperature. The following
are some of the chief difficulties:-
1) The generation of heat by the friction of the pision against the cylinder
walls, of the piston rod in the glands, and in some cases of the valves and their
operating gear.
2) The conduction of heat through the cylinder walls from outside sources
during the expansion of the air.
3) The fluctuation of temperature within the expansion cylinder, which causes
heat to be absorbed by the cylinder walls and piston at the beginning of the
expansion stroke, and emitted to the air towards the end of the stroke.
In order to effect improvement in respect of the first point, it is important
to reduce, as far as possible, the friction between solid surfaces with which the
air may come in contact or proximity during expansion.
The second point indicates the desirability of keeping the expansion cylinder
or chamber small, to minimise the area of surface exposed to the atmosphere and
surrounding objects.
The third point indicates the desirability of employing a motor wherein the
expansion takes place with very little, if any, fluctuation of temperature of the
air in contact with any particular part of the solid surface.
It is impossible to realise all these objects simultaneously in a piston and
cylinder motor, whilst expanding the air in a high ratio of volumes, because
the second and third objects could only be accomplished by using high speed com-
pound engines, which would be quite unsuitable for attaining the first object.
Another class of apparatus which has been used for obtaining very low tem-
peratures, and thereby liquefying gases, depends on the cooling effect of a jet
of air issuing under high pressure from a pipe or receiver through a very small
orifice, or cock, the air being cooled whilst under pressure by part of the cold air
discharged, and sometimes assisted by other means. The extent of cooling by
the high pressure jet is limited to the thermal equivalent of the work done in dis-
placing the atmosphere, as was proved by Joule in 1845, and it follows that only
a very small fraction of the air discharged can be liquefied by the action of the
jet.
The arrangement entirely disposes of the element of friction of solid surfaces
in the expansion chamber, and also realises the desirable conditions of a small
chamber with little or no fluctuation of the temperature of its parts during the

page_text: A
process of expanding the air; but the very large amount of work done in over-
coming the resistance of the orifice (apart from the displacement of the atmos-
phere) is entirely converted into heat which remains in the expanded air.
high cooling efficiency is therefore impossible, although extremely low tempera-
tures may be obtained with such apparatus if a relatively large amount of energy
is expended in compressing the air.
By my present invention the expansion of the air is carried out in a motor of
the turbine type running at a high speed and doing external work. Any suitable
and efficient form of turbine may be used, but it is desirable to keep the shaft
or spindle bearings and thrust block (if any) at some little distance from the
working barrel or chamber, for the double purpose of avoiding friction of solid
surfaces on lubricants near the cold air and to prevent the oil supply being frozen.
The extension of the shaft to the bearing may be enclosed in a tube, leaving a
small annular space in communication with the working air chamber but protected
from any considerable circulation of cold air.
The arrangement of apparatus according to my invention is as follows:-
A. An air compressor driven by power from any available source. I prefer a
compound compressor, with intermediate water coolers, for high pressures.
B. A pipe coil or other apparatus through which the compressed air passes on
leaving the compressor, and is cooled by the external application of water.
C. In some cases it may be desirable to effect further cooling of the compressed
air by passing it through another coil having a circulation of cold brine supplied
by an ammonia refrigerating machine or other suitable apparatus.
D. Further cooling of the compressed air is effected after leaving B (or B and
C) by passing it through another coil or series of pipes cooled externally by a
portion of the cold air discharged by the turbine, which may pass back to be
compressed again with some fresh air.
Suitable traps for removing condensed moisture or snow, should be provided
in connection with B, C and D.
E. A turbine motor wherein the compressed air is expanded approximately
adiabatically, and cooled, driving a shaft and doing external work either by
assisting to compress the air in A, or driving some other machine requiring
power. The case or barrel of the turbine should be enclosed in a jacket or box,
through which part of the cold exhaust air passes on its way to the cooler D,
and further by a suitable non-conducting covering.
F. A chamber or box into which the exhaust from the turbine is discharged.
If the apparatus is used for liquefying air or other gases, the high ratio of
expansion required may be secured either by a very high initial pressure in the
turbine with the discharge a little above the atmospheric pressure, or by a
moderately high initial pressure and a vacuum in the exhaust box, maintained
by air pumps. In the latter case, the liquefied portion of the discharge from the
turbine is preferably pumped out of the exhaust box by a separate pump.
Dated this 19th day of December 1898.
Improvements in Apparatus for Refrigerating and Liquefying Air or
other Gases.
I, EDGAR CHARLES THRUPP, Civil Engineer, of Southdene, Ashley Park Road,
Walton-on-Thames, in the County of Surrey, do hereby declare the nature of

page_text: this invention and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement: —
In refrigerating apparatus depending on compressing air, then cooling it, and
then expanding it in a cylinder against a piston doing mechanical work, the
cooling of the air to extremely low temperatures cannot be effected on account
principally of the generation of heat by the friction of the piston against the
cylinder walls of the piston rod in the glands, and, in some cases, of the valves
and their operating gear and the conduction of heat through the cylinder walls
from outside sources during the expansion of the air and also on account of the
fluctuation of temperature within the expansion cylinder, which causes heat to
be absorbed by the cylinder walls and piston at the beginning of the expansion
stroke and transmitted to the air towards the end of the stroke.
It is therefore important to reduce, as far as possible, the friction between
solid surfaces with which the air may come in contact or proximity during
expansion and to keep the expansion cylinder or chamber small so as to have
as little surface as possible exposed to the atmosphere and surrounding objects
and further to employ a motor wherein the expansion takes place with very
little, if any fluctuation of the temperature of the air in contact with any par-
ticular part of the surface.
It is impossible to obtain all these advantages simultaneously in a piston and
cylinder motor whilst expanding the air in a high ratio of volumes.
Another class of apparatus which has been used for obtaining very low tempera-
tures and thereby liquefying gases, depends on the cooling effect of a jet of air
or gas issuing under high pressure from a pipe or receiver through a very small
orifice or cock, the air being cooled whilst under high pressure by part of the
cold air discharged assisted sometimes by other means.
The arrangement entirely disposes of the element of friction of solid surfaces
in the expansion chamber, and also realises the desirable conditions of a small
chamber with little or no fluctuation of the temperature of its parts during the
process of expanding the air but the very large amount of work done in over-
coming the resistance of the orifice (apart from the displacement of the atmos-
phere) is entirely converted into heat which remains in the expanded air. A
high cooling efficiency is therefore impossible, although extremely low tempera-
tures may be obtained with such apparatus if a relatively large amount of energy
be expended in compressing the air.
According to my invention the expansion of the air is carried out in a motor
of the turbine type running at a high speed and doing external work. Any
suitable and efficient form of turbine may be used, but it is desirable to keep
the shaft or spindle bearings and thrust block (if any) at some little distance
from the working barrel or chamber for the double purpose of avoiding friction
of solid surfaces or lubricants near the cold air, and preventing the oil supply
being frozen.
If the apparatus be used for liquefying air or other gases, the high ratio of
expansion required may be secured either by a very high initial pressure in the
turbine with the discharge a little above the atmospheric pressure, or by a moder-
ately high initial pressure and a vacuum in the exhaust box maintained by air
pumps. In the latter case the liquefied portion of the discharge from the turbine
is preferably pumped out of the exhaust box by a separate pump.
I will now describe with reference to the accompanying drawings an arrange-
ment of apparatus according to my invention premising that I do not limit
myself to the particular details of the arrangement illustrated as any convenient
and efficient means the equivalents of those set forth may be employed.
Figure 1 is a general diagrammatic plan of the apparatus. Figure 2 is a
vertical section of parts of the apparatus on the lines 1, 2, 3. Figure 1 and
Figure 3 is an enlarged vertical section of part of the turbine motor.
S, S., S, represent the cylinders of a triple expansion steam engine and L is its

page_text: crank shaft carrying the fly wheel K and driving a three stage compressor the
cylinders of which are marked A, A, A, having intermediate water coolers W₁ W2.
The compressed air on leaving the third compressing cylinder A³ passes to the
cooler B which has a circulation of water to reduce the temperature of the com-
pressed air to that of the atmosphere, or thereabouts, and then it passes through
the auxiliary cooler C to the main cooler or interchanger D or it may pass directly
to the said interchanger from the cooler B by the pipe indicated by the dotted
lines M.
The auxiliary cooler C consists of a coil or coils of piping in a tank C² the
compressed air passing through the piping and cold brine (which may be cooled
for example by an ammonia refrigerating machine) circulating through the tank
entering at N and leaving at N³. Further cooling of the compressed air is
effected in the interchanger or main cooler D in which the cooling medium is air
discharged from the turbine E. The compressed air passes through a series of
concentric spiral coils contained in annular spaces arranged so that whilst
the compressed air passes alternately upwards and downwards in successive coils
travelling towards the centre of the apparatus, the cold exhaust air enters at the
bottom of the central compartment and travels in the reverse direction. This
will be understood by reference to Figure 2 wherein the direction of travel of
the cold exhaust air alternately upwards and downwards as indicated by the
arrows.
The compressed air pipe emerges from the bottom of the central compartment
of the interchanger D and passes to the turbine E and is fitted with a stop-
valve P and may also be fitted with a throttle valve actuated by governor gear
to control the speed of rotation of the turbine if desired. If moisture be con-
tained in the compressed air it may be condensed or converted into snow in pass-
ing through the coolers B C D and may be collected or intercepted by introducing
traps at any suitable point on the compressed air pipe circuit for instance as
indicated at 0, 0, in Figure 1 consisting of boxes or cylinders of larger diameter
than the compressed air pipe. The traps are shewn in duplicate with stop valves
on the inlets and outlets so that one at a time can be shut off from the compressed
air circuit and opened for removing the deposited moisture or snow. The tur-
bine E shewn in the drawings is an adaptation of the well known radial flow
compound steam turbine. The compressed air enters the working barrel of the
turbine E at the centre by the pipe d and travels right and left as indicated by
the arrows in Figure 3 impinging on the projecting vanes carried by the discs X
mounted on the shaft X and directed by fixed guide blades carried on annular
discs projecting inwards and forming the barrel. The covers y direct the air
or gas first inwards as it exhausts from the turbine allowing the liquid to escape
at the circumference through a passage communicating with the pipe U leading
to the reservoir G. QQ is the centre line of the machine in Figure 3, the half
not shewn being substantially a repetition of the half shewn. Fis the exhaust
box surrounding the turbine and R is an annular space surrounding the shaft Xª
where it passes through the non-conducting jacket F2 of the exhaust box. The
object of the spaces R is to keep the thrust or guide blocks S and the bearings T 4
at a distance from the motor parts of the turbine and from the exhaust box for
the purpose aforesaid.
The liquefied portion of the exhaust may pass away by the pipe or passage U
into the reservoir G which is provided with a draw off pipe g at the bottom, a
closed top and an overflow or outlet pipe V for gas expelled as the liquid runs 5
in, or afterwards produced by the evaporation of the liquid. The gas which
passes out of the reservoir through the pipe V may be passed up the annular
space outside the reservoir and allowed to escape through the interchanger D
together with the exhaust from the turbine. On leaving the interchanger D
the exhaust passes into the chamber H containing a central tube h open to the 5
atmosphere at the top and to the chamber H at the bottom. Fresh air is drawn

page_text: in through the central tube h to make up for the portion which has been liquefied
and in passing down the tube it is cooled by the air in the surrounding cham-
ber H and its moisture condensed. The condensed moisture is drawn off by a
trapped drain ha and the fresh air then mixes with the exhaust air and passes by
the passage h³ to the first compression cylinder A. If the moisture be separated
as snow it is preferable to employ duplicate separators similar to H provided with
valves to shut off one of the said separators at a time for removing the snow.
The turbine shaft X is extended beyond one bearing and may drive a counter
shaft by friction gearing as shewn at 1 in Figure 1, and assist in driving the
compressors by a belt passing from the pulley Jon the said counter-shaft to the
fly wheel K, or it may drive any other machine such as a dynamo electric machine.
The cold portions of the apparatus are all enclosed by non-conducting cover-
ings which are indicated by the thick sectioned portions.
The form of turbine motor shewn in the drawings is, I believe, that best suited
to the purposes of my invention for obtaining the lowest temperatures but I may
use any other suitable form of turbine motor such for instance as one resembling
the De-Laval steam turbine or the Pelton water wheel or reaction turbines.
The apparatus may be used for separating mixed gases which liquefy at different
temperatures, and if so used it may be preferable to prevent any of the gas
produced by evaporation in the reservoir from mixing with the exhaust gas
from the turbine. It may also be preferable not to return any of the latter to
the compressor, but to take in an entirely fresh supply of mixed gases at each.
stroke of the compressor.
If the liquefying temperatures of the gases are not very widely different it
may happen that both will be liquefied simultaneously and the separation may
be effected more or less perfectly by allowing the liquid mixture to stand in a
reservoir whilst the gas having the lower boiling point evaporates. A convenient
way of carrying out this principle is by 'dividing the reservoir G, Figures 1 and
2 into two or more compartments with pipe connections to enable them to be
filled one at a time and allowed to rest while the other compartments are being
filled in turn. The gas or gases evaporated from the reservoirs may be used to
cool the compressed mixed gases in an interchanger of similar construction to D
or working on the same principle. This plan is suitable for separating liquid
oxygen from liquid nitrogen by evaporating off the nitrogen. If the oxygen is
required in the gaseous state it may also be used for cooling the compressed air
in another interchanger.
If the liquefying temperatures of the mixed gases are widely different, the
degree of compression may be arranged so that only one of the gases is liquefied
and the liquid may then be delivered into a reservoir having no direct con-
nection with the exhaust gas passages in the interchanger, but the liquid may be
evaporated and passed through a second coil of pipes in the interchanger and
discharged into a gas holder or other receptacle as required. The apparatus may
be used in this manner for separating ethylene (and other more easily conden-
sible hydrocarbons) from ordinary coal gas, or for separating hydrogen from coal
gas or water gas by liquefying the other constituents of the mixture.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed, I declare that what
I claim is:-
1. In apparatus for refrigerating, or liquefying, air, or other gas, or gases,
the use of a turbine motor in which the air, or gas, or gases, is, or are expanded
and caused to do external mechanical work, in combination with means for com-
pressing the air, or gas, or gases, and for cooling it, or them, whilst under pres-
sure; substantially as hereinbefore described.
2. In apparatus for refrigerating, or liquefying, air, or other gas, or gases,
the use of a turbine motor in which the air, or gas, or gases, is, or are expanded,

page_text: and caused to do external mechanical work, in combination with means for com-
pressing the air, or gas, or gases, and for cooling it, or them, whilst under pres-
sure, the thrust, or guide blocks, and bearings, of the said turbine motor, being
kept at a distance from the motor parts of the said turbine motor, substantially
as hereinbefore described and illustrated in the accompanying drawings.
141
1000
DepremDCA
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.