US2059877A

US2059877A - Refrigeration

Info

Publication number: US2059877A
Application number: US733573A
Authority: US
Inventors: Kogel Wilhelm
Original assignee: Servel Inc
Current assignee: Servel Inc
Priority date: 1933-07-15
Filing date: 1934-07-03
Publication date: 1936-11-03
Anticipated expiration: 1953-11-03

Description

Nov. 3, 1936. w. G. KOGEL 2,059,877

REFRIGERATION Filed Jui s; 1934 s Sh ets-Sheetl v INVENTOR Ja /dz ATTORNEY.

Nev. 3, 1936. w. G. KOGEL REFRIGERATIO N Filed July :5, 1954 3 Sheets-Sheet 2 f 3 I. IL TI i-TEL-UTFTIUTFTHH INVENTOR.

4 ATTORNEY.

Nov. 3, 1936; W. G. KOGEL 2,059,877

REFRIGERATIbN Filed July 5, 1954 s Sheets-Sheet s INVENTOR.

0% ATTORNEY.

Patented Nov. 3, 1936 UNITED STATES REFRIGERATION -Wilhelm Kiigel, Stockholm, Sweden, assignor, by

mesne assignments, to Servel, Inc Dover, DeL, a corporation of Delaware A plication July}, 1934. serial No; 133,51: 1 In Germany July 15, 19s:

19 Claims. (oi. Z -119.5)

My invention relates to refrigeration and more particularly to production of refrigeration by evaporation and diffusion of refrigerant fluid- .into an auxiliary inert gas.

g In refrigerating systems of this type, it is advantageous to conduct liquid refrigerant by gravity into the presence of the inert gas and in counterfiow thereto. It has therefore been proposed to flow the inert gas upwardly in the no evaporator or cooling element. When the refrigerant used is of greater specific gravity than the inert gas and diflerences in specific gravity are utilized to cause the gas fiow, the column of in the evaporator tends to exert a downward to force, which, in the case of the desired upward flow in the evaporator, opposes the gas circulation. The chest of this opposite force isgreatest at starting and renders the direction of gas how at that time uncertain.-

it is an object of my invention to provide a refrigeration system of this type in which the gas flow is initiated in the desired direction and thereafter aided in the same direction. Another object is to provide such a system operable to p produce cooling simultaneously at a plurality oi temperatures and therefore advantageous ror refrigerators requiring both a freezing tempera ture and a higher food preserving temperature.

in accordance with my invention, I obtain the shove objects by providing a member or second evaporator in a downward path of how oi the gas from the usual low temperature evaporator, and conduct refrigerant liquid to the latter through the second evaporator, whereby, on starting, the liquid reaches the additional evaporotor first and creates a column of descending frigerant vapor which is heavier than thus creating a circulating iorce red direction before the above men produced by the evaporation of refrigerant into the column of ascending gas. The temperature diflerence is due to the difference in partial pressures of the refrigerant in the two columns of 55, gas.

My invention, together with the objects and.

' advantages thereof, will be'more fully understood from consideration, of the following description and the accompanying drawings forming part of this specification, and of which: s

Fig. 1 showsschematically a refrigeration system. embodying my invention;

Fig; 2 is a'partial-view of a system shown in Fig. land illustrating a modification of my invention; v to Fig. 3 is a view similar to thator 551g. 1 and illustrating a-i'urther modification oi my inventiom' i Fig. 4' is a moreor'less schematic view of a refrigeration system comprising a modification iii of that shown in Figs. 1 and 3 and embodying custom of my invention; and

i-i 'ig. 5 is a partial view illustrating a modification of my inventioh embodied in an apparatus like that in Fig. 4..

I i shall point out the principle of my invention in'connection with the embodiment illustrated in Fig. i of the drawings and thereafter direct attention to the variations encountered in the several modifications illustrated in Figs. 2 through s. Referring then to Fig. l, the refrigeration system illustrated is-generaly oithe nature of a system disclosed in Patent 1,609,334 to Von Plat, et al., to which reference may had for a complete understanding of the operation. Briefly, however the refrigeration system iu= eludes as essential parts a generator a condenser ii, an evaporator it, and an absorber is. The generator iii is heated inauy suitable manner as, for instance, by a gas retu ner to so 35 arranged that the humerfleme projects into the lower end of aheating due as which extends vertically through the generator is. The oh sorher i3 and condenser it may he cooled in any desirm manner as, for instance, Toy air, tooth oi no these parts losing shown provided with heat rediation fins for this purpose. The oheorher i8 and the generator iii are interconnected through a liquid heat exchanger id tor circulation thereoetween oi absorption iiquidthe lioguid circulotionbeing caused by thermosiphonic action in o thermosiphon conduit i7 having its lower end formed as a coil it around the lower"- end of the heating flue I! and in thermal exchange relation therewith. The evaporator i2 and the abso sorber 98 are interconnected through a gas heat exchanger I! for circulation of gas therebetween as hereinafter described. The condenser II is connected to receive vapor from the generator ll and deliver liquid to the evaporator ii in a iii! charged, for instance, through a charging Plug, not shown, on the absorber I 3, with a suitable solution of refrigerant fluid in an absorption liquid, such as a water solution of ammonia, and an inert pressure equalizing gas, such as hydrogen. The hydrogen is admitted into the system at a pressure corresponding to the condensing pressure of ammonia .at a predetermined temperature which is preferably a high room temperature in the case of air cooling.

In operation,-ammonia vapor is expelled from the gas heat exchanger l9 and upwardly with-.

in the evaporator l2 for precooling of the ammonia from the condenser temperature downwardly toward the evaporator temperature, as well known in the art.

In the evaporator l2, ammonia evaporates and diffuses into the hydrogen which enters the lower part of the evaporator through conduit 23. The resulting gas mixture or strong gas" flows from the upper part of the evaporator l2 through a conduit 24, a receiver 2!, a conduit 25, the outer space 21 of the gas heat exchanger is, and conduit 28 to the lower part of the absorber l3. Ab-

sorption solution from which" ammonia has been expelled by heating in the generator Ill may be referred to as weak solution, and flows from the lower part of the generator through conduit 29, the liquid heat exchanger l6 and conduit into the upper part of the absorber It. In the absorber, ammonia is dissolved out of the strong gas into the weak. solution. The result ing weak gas flows from the upper part of the absorber I; through conduit 8|, the inner passages 82 of the gas heat exchanger is, and conduit 22 back to the lower part of the evaporator i2, thus completing the gas circuit. Enriched absorption solution flows from the lower-part of the absorber ll through a conduit 33, theliquid heat exchanger l8, and the thermosiphon ele-' ment I! into the upper part of the generator [2, thus completing the absorption liquid circuit.

The above described circulation of gas between the absorber l3 and evaporator l2 takes place after the system has been in operation for an appreciable length of time and is caused principally by the action in the absorber I! which creates a rising column of gas flowing from the absorber to the evaporator which .is lighter than the descending column of gas flowing from the evaporator to the absorber. However, at starting, evaporation of ammonia into the hydrogen in the evaporator I2 creates'a partial column of strong gas which is heavier than the hydrogen or weak gasand tends .to oppose or at least make uncertain the desired upward flow of gas imthe evaporator. I therefore provide the above-mentioned receiver 25 in-the path of flow of gas from the upper part of the evaporator to the lower part of the absorber and provide a conduit 34 connecting the receiver 2| with the vessel 2! so that the lower part of the receiver 25 receives liquid ammonia. The upperend of conduit 26 opens into the receiver 25 above the liquid level therein which is determined by the overflow level at the From the lower part of the manner hereinafter described. The system is upper end of conduit 22 in the evaporator I2. I preferably arrange the connecting points of conduit 34 with the vessel 2i and receiver 25 with respect to the upper end of the conduit 22 in the evaporator l2 so that, at starting, liquid ammonia from the condenser ll flows from the vessel 2| through conduit 34 into the receiver 25 just prior to overflow of liquid ammonia from the upper end of conduit" in the evaporator l2. With this arrangement, ammonia in the receiver 25 evaporates into the hydrogen in the upper part of this receiver, forming a, heavier gas mixture which descends through conduit 26 toward the absorber and starts the circulation of gas in the desired direction prior to or coincidentally with formation of the abovementioned heavier gas column in the evaporator l2 which is created upon evaporation of the ammonia into the hydrogen. In effect,a column of strong gas is created in conduit 26 which at least balances the column of gas in the evaporator l2 whereby the gas circulation is created in the desired direction by the action in the absorber l3. In operation, the column of gas in conduit 26 is heavier than the column of gas in the evaporator 12 for the reason that ammonia in the receiver 25 may be caused to evaporate into the strong gas flowing from the top of the evaporator through conduit 2% into the receiver 25 at a higher temperature than the evaporation of ammonia into the weak gas in the evaporator l2. Receiver 25 may therefore be referred to as a second evaporator or a high temperature evaporator. The cooling eifect of the liquid in the receiver 25 and the gas in conduit 26 may advantageously be used for cooling the air in a refrigerator by locating these elements, along 1 with the low temperature evaporator l2, in a re- ,modification bf my invention, I provide a conduit 28 connected from the upper part of the evaporator l2 to the outer passage 2'1 of the gas heat exchanger is. A receiver 31 is provided with an overflow conduit 38 into the evaporator l2 and is connected to receive liquid ammonia from the condenser, not shown, through conduit 39. From within the upper part of the vessel 31 and above the liquid level therein as determined'by said overflow of conduit 38, I provide a conduit 40 having its other end connected to said conduit 38. The upper part of the receiver 31 is in permanently open gas communication with the upper part of the evaporator through the overflow conduit 38, which latter is arranged so that it is never completely filled with liquid, as shown. If the overflow conduit 38 is otherwise arranged so that it may be filled with liquid, an equalizing conduit should be provided from the upper part of the receiver 31 to the gas circuit.

In operation, liquid ammonia, which enters the receiver 3! from the condenser through conduit 39, evaporates and diffuses into the hydrogen in the upper part of receiver 31, forming a heavier gas mixture which descends through ously described in connection with Fig. l to cause circulation in the desired direction, name- 1y upwardly in the evaporator i2. In this modiflcationalso, since the gas in the upper part of the receiver or auxiliary evaporation vessel 31 flows from the upper part of the evaporator l2, the gas flowing through conduit. 40 into the conduit 36 is heavier than the gas in the Fig. 1 are replaced by an evaporator- 42 somewhat similar to the evaporator l2, and different means is provided for supplying liquid refrigerant to the second or high temperature evaporator 42. Like parts in Figs. 1 and 3 are indiknown in the art, with a recessed casting or other means for receiving trays containing water or other substance to be frozen. It will he understood that the evaporator l2 illustrated in Figs. 1, 2 and 3 and the evaporator 42 illustrated in Fig. 3 need not be of the type illustrated but may be of any suitable type such as the coil type evaporator illustrated in Fig. 4.

From the upper part of the generator l0, va- I por flows through a'conduit 45 to a condenser 46 In the latter, the refrigerant vapor is condensed to liquid which flows through a conduit 41 to nected by. a conduit 49 to a rectifier jacket around the vapor conduit 45 so that the rectifier jacket 50 contains liquid refrigerant to the same level as that in the collecting vessel .48. The

. liquid level in the collecting vessel 48 is determined by the overflow conduit 22 which extends through the gas heat exchanger l9 into the upper part of the evaporator l2 as previously, described in connection with Fig. l. The upper part. of the collecting vessel 48 is connected to the upper part of the evaporator 42 by a conduit 5!. The conduitil is provided with heat radiation fins 52 or any other suitable cooling means, forming a condenser; A conduit 58 is connected at one end to the conduit 49 and at the other. end to the conduit 52, and extends in thermal conductive relation with the rectifier jacket 50, as shown. Liquid refrigerant also stands in conduit 53' to the same level as that in the collecting vessel 48 and :the rectifier jacket 50. Due to said thermal association with the rectifier jacket 50 refrigerant vapor is formed in conduit 58 and flows into conduit 51 in which the vapor is condensed to liquid. This supply of vapor could also be obtained by connecting conduit 53 to the upper part. of the rectifler jacket 58 instead of to the conduit 48.- Liquid'refrigerant formed by condensation in conduit. flows into the evaporator 42 where it evaporates and diffuses into the hydrogen or other inert gas, forming a heavier-column of gas in the path of flow from the evaporator l2 to the absorber l3, thereby instigating or maintaining gas circulation in the desired direction.

collecting vessel 48. The latter is con- 3 During operation of the system, the higher temperature of the evaporator 42 depends upon the partial pressure of refrigerant in the gas which flows from the upper part of the evaporator l2 through conduit 43 into the upper part of the 5 evaporator 42. r i ferring now to Fig. 4 of the drawings, the refrigeration system illustrated is similar to that disclosed in an application Serial No. 673,815 of Albert R. Thomas, to which reference may be had for a complete description of construction and operation. Briefly, however, the generator 54 is of a so-called horizontaltype comprising a horizonal vessel 55 divided by a partition into a strong liquid chamber 56 and a. weak liquid chamber .51. The lower end of a standpipe 58 communicates with the weak liquid chamber 5'! and a thermosiphon conduit 59 extends from within the strong liquid chamber 58 into the upper part of the standpipe 58.

In this system, the absorber 60 is cooled by a secondary vaporization-condensation element including a cooling coil 5| arranged in thermal conductive relationaround the absorber and, connected by conduits $2 and 83 to'an air-cooled 2 condenser 64. This absorber-cooling element is charged with a suitable refrigerant such as methyl chloride which vaporizes in the coil 5! and condenses in the condenser 54.

. The evaporator 65 is of the coil type comprising a lower section 58 suitably arranged for freezing water or the like in so-called ice trays, and an upper section 61 having anaextensive heat transfer surface for cooling the air in the thermally insulated storage compartment 68. 3

This system may be charged similarly to that described in connection with Fig. 1 by sealing .lower part of the absorber 6!] through conduit 12, the liquid heat exchanger 10, conduit ,1 the lower. part of an analyzer vessel I4, conduit I the strong liquid chamber 56,: and the thermosiphon element 59 into the upper end-of the standpipe 58.

evaporator or through conduit I8, chamber 11 in the upper end of a gas heat exchanger 18, the inner passage 19 of the gas heat exchanger, and conduit to the lower part of the absorber 60. Weak gas flows fromlthe upperv part of the absorber 50 through conduit 8i, the outer passage 82 of the gas heat exchanger I8 'and conduit 83 to the lower part 66 of the evaporator.

Rich gas flows from the upper part 61 ofthe up A drain for unevaporated liquid is provided by analyzer vessel 14, the vapor flows through a con- 7 duit 86 to the. upper end of an air-cooled'coil type condenser 81. Liquid ammonia formed in the condenser 81 flows into a collecting vessel- 88. The latter is vented to the gas circuit ,for

equalization or return of trapped hy- 7' conduit Ii of the gas heat exchanger 18, which separates the inner passage 1! and outer passage I2, is extended upwardly into the chamber 11 at the upper end of the gas heat exchanger. The lower part of the collecting vessel 88 is connected to the lower part of the chamber 11 by a conduit 92 and the lower part of the chamber 11 is connected by an overflow conduit 93' to the upper part I! of the evaporator 65. Thus, liquid ammonia from the condenser 81 stands in the vessel 88 and the chamber 11 to a level determined by the overflow point of conduit 93 into the evaporator. In chamber 11, ammonia evaporates into the hydrogen, forming a heavier gas mixture which descends through the inner passage 19 ofthe gas heat exchanger 18 to instigate or maintain the gas circulation between the evaporator and absorber G0 in the desired direction, namely, upwardly through the evaporator 85.

In the modification illustrated in Fig. .5, I provide a receiver 94 corresponding to the receiver 31. illustrated in Fig. 2. The receiver 91 is connected to receive liquid ammonia from the condenser or a collecting vessel through conduit II and is provided with an overflow connection II to the upper part 61 of the evaporator II which is the same as that described inv connect-ion with Fig. 4. The upper part of the receiver II is connected between the upper part I! of the evaporator and the chamber 11 of the gas heat exchanger 18 by conduits 91 and 98. From the upper part of the receiver 94, a descending conduit 99 is connected to the inner passage II of the gas heat exchanger. The receiver It and the conduit 89 are located within the storage chamber II of the refrigerator together with the evaporator I5, and the conduit II is preferably provided with heat transfer fins III.

In operation, liquid refrigerant in receiver 94 evaporates into the hydrogen, forming a heavier gas mixture which descends through conduit II into the inner passage 19 of the gas heat exchanger II, thus instigating or maintaining gas circulation in the desired direction, namely, up-

wardly through the evaporator 85.- The receiver' I4 and conduit II serve in addition to the upper portion I1 of the evaporator II to cool the air in the storage compartment 88. ,If desired, the upper portion II of the evaporator may be omitted and the upper end of the lower evaporator section II connected directly to the upper part'of the receiver II.

Various other changes and modifications will be readilyapparent to one skilled in the art, wherefore my invention is 'not limited to'that which is shown in the drawings or described in the specification but only as indicated in the following claims.

What I claim is:

1. A method of refrigeration which includes' expelling refrigerant vapor from solution in an absorbent, condensing the expelled vapor to liquid, conducting the liquid into contact with an inert gas at a first place tocause evaporation ofsome of the liquid, utilizing the difference in specific gravities of theiresulting gas mixture and the purer inert gas to initiate circulation of the inert gas, subsequently conducting the liquid into further contact and counterfiow with the circulating gas at a-second place in which said gas flows upwardly toward said first place, and absorbing the refrigerant vapor out of the inert gas into the absorbent from which it was previously expelled and at a place in an upward path of flow/of the circulating gas.

2. a method of refrigeration which includes expelling refrigerant vapor from solution in an absorbent, condensing the expelled vapor to liquid, conducting the liquid into contact with inert gas in a first evaporator to cause evaporation of some of the liquid, utilizing the difference in specific gravities of the resulting gas mixture and the purer inert gas to initiate circulation of the inert gas. subsequently conducting the liquid into further contact and counterfiow with the circulating gas in a second evaporator through which said gas flows upwardly toward said first evaporator, and absorbing the refrigerant vapor out of the inert gas into said absorbent in an absorber through which gas flows upwardly toward said second evaporator.

3. A method of refrigeration which includes distilling refrigerant fiuid from solution in a liquid absorbent, circulating inert gas between a place of evaporation and a placeof absorption, each of said places being in a rising path of flow of said gas, circulating liquid absorbent downwardly through said place of absorption, and conducting distilled refrigerant liquid into the presence of said inert gas first in a descending path of fiow of said gas and. then downwardly in said place of evaporation.

4. A method of refrigeration which includes distilling refrigerant fiuid' from solution in a liquid absorbent, circulating inert gas between an evaporator and an absorber, each" being in a rising path of fiow of said gas, flowing liquid absorbent downwardly through said absorber, and conducting distilled refrigerant liquid first into a second evaporator in a descending path of flow of said gas and then into said first evaporator.

5. A method of refrigeration which includes circulating inert gas between an evaporator and an absorber, each being in a rising path of fiow of saidgas, conducting refrigerant liquid first into a second evaporator in a descending path offiow of said gas and then into said first evaporator, and flowing liquid absorbent through said absorber. I

6. Refrigeration apparatus including a cooling element comprising a first member adapted for upward flow of gas and downward fiow of liquid therethrcugh and a second member adapted for downward flow of gas and communicating at its upper end with the upper end of said first member, an absorber interconnected with said cooling element for circulation of inert gas therebetween, a generator interconnected with said absorber for circulation of absorption liquidtherebetween, a condenser connected to' receive refrigerant vapor expelled from solution in the absorption liquid in saidgenerator, a receiver for liquid in open communication with the second member of saidcooling element, an overflow connection for liquid from said receiver totheupperpartofthefirstmemberofsaid cooling element and a conduit for liquid from said condenser to said receiver. Y 7. In a refrigerator,. a thermally insulated storage compartment, a' cooling element in said 76 with the upper end of said pipe coil, an absorber interconnected with said cooling elements for circulation of inert gas therethrough in series,

a generator interconnected with said absorber for circulation of absorption liquid therebetween, a condenser connected to receive refrigerant vapor expelled from solution in the absorption liquid in said generator, a receiver for liquid in open communication with said second cooling element, an overflow connection for liquid from. said receiver to the upper part of said first cooling element, and a conduit for liquid fromsaid condenser to said receiver.

8. In'a refrigerator, a thermally insulated storage compartment, a cooling element in said compartment adapted for upward flow of gas and downward flow of liquid therethrough, a second cooling element in said compartment adapted for downward flow of gas and communicating at its upper end with the upper end .of said first cooling element, an absorber interconnected with said cooling elements for circulation of .inert gas therethrough in series, a generator interconnected with said absorber for circulation of absorption liquid therebetween, a condenser connected to receive refrigerant vapor expelled from solution in the absorption liquid in saidgenerator, a receiver for liquid in open communication with said second cooling-element, an; I

overflow connection for liquid from said receiver to the upper part of said first cooling element,

of said pipe coil, an absorber interconnected with said cooling element and said descending conduit for circulation of inert gas therethrough in series, a generator interconnectedwith said absorber for circulation of. absorption liquid therebetween, a condenser connected to receive refrigerant vapor expelled from solution in the absorption liquid in said generator, a receiver for liquid in open communication with said descending conduit, an overflow connection for liquid from said receiver to the upper part of said cooling element, and a conduit for liquid from said condenser to said receiver; 1

10. In a refrigerator, a thermally insulated storage compartment, a cooling element in said compartment comprising a pipe coil adapted for upward flow of gas and downward flow of liquid therethrough and a descending conduit for gas communicating at its upper end with the upper end of said pipe coil, an absorber interconnected with said cooling element for circulation of in ert gas therebetween, a generator interconnected with said absorber for circulation of absorption liquid therebetween, a condenser connected to receive refrigerant vapor expelled from solution in the absorption liquid in said generatorgia receiver for liquid in open communication with the upper end of the descending conduit of said cool H ing element, anoveriiow connection ftr liquid from\ said receiver tothe upper part of thepipe coil of said cooling element, and a conduit for liquid from said condenser to said'receiver.

11. Refrigeration apparatus including a cooling element adapted for upward flow of gas and downward flow of liquid therethrough, a member adapted for downward flow of gas and communicating atits upper end with the upper endof said cooling element, an absorber interconnected with said cooling element and said mem- 'ber for circulation of inert gas therethrough in series, a generator interconnected with said absorber for circulation of absorption liquid there between, a condenser connected to receive refrigerant vapor expelled from solution in the absorption liquid in said generator, a receiver for liquid in open communication with said member, an overflow connection for liquid fromsaid receiver to the upper part of said cooling element, and a conduit for liquid from said condenser to said receiver.

12. In an absorption refrigeration system, a plurality of evaporators and an absorber interconnected for ;circulation of gas therethrough in series, one of said evaporators providing a rising path of flow for said gas and another of said evaporators'providing a descending path of flow for said gas, means for supplying refrigerant liquid to said second evaporator, and'means for conducting liquid from said second evaporator to said first evaporator.

-13. In an absorption refrigeration system,- an evaporator and an absorber interconnected for circulation of gas therebetween and upwardly through each, a member forming a descending path for flow of gas from said evaporator, and means including said member for conducting liquid refrigerant to said evaporator, the liquid being brought into contact with gas in said member.

. 14. In an absorption refrigeration system, an

evaporator and an absorber interconnected for circulation of gas therebetween and upwardly through each, a member forming a descending path in the flow of gas from said evaporator, and

means for initially supplying liquid refrigerant to said member prior to entrance of liquid refrig erant into said evaporator. 1

15. An absorption refrigeration system including an evaporator and an absorber interconnected for circulation of gas therebetween and upwardly through each, and means for conducting liquid refrigerant to said evaporator in contact with said gas in (a downward path of flow of the latter from said evaporator.

16. In an absorption refrigeration system, a cooling element and an absorber interconnected for circulation of gas therebetween, said cooling element providing. alternate up and down paths of flow for said gas in series, and means for conducting liquid refrigerant into the presence of gas in said cooling element, first in one of said down paths and then'in a preceding up path.

1'7. In a method of refrigeration which includes the steps of evaporating and diffusing liquid refrigerant into an auxiliary inert gas, absorbing refrigerant vapor out of the inertgas, and utiliz ing the difference in specific gravity of the gas mixture to initiate and maintain circulation of the inert gas, that improvement which consists in bringing the liquid into contact with the gas at a place in an upward path of flow of the gas, and conducting the liquid to said place in a path which brings it first into contact with the gas in a downward path of flow thereof.

it. In a method of refrigeration which includes 75 the steps of evaporating and diflusinl liquid-refrigerant into, inert gas, absorbing refrigerant vapor out of the gas and utilizing the difference in specific gravity of the mixture to cause circulation of the gas, that improvement which consists in conducting liquid refrigerant into contact with the gas at several places so' that it arrives at one place prior in time to reaching a second place, said places being arranged so that circulation of the gas with upward fiow at said second place is initiated and maintained by evaporation of liquid at said first place. 19. In a method of refrigeration which includes the steps of evaporating and difi'using rca,oso,a77

frigerant liquid into inert gas and absorbing refrigerant vapor out of the gas at several places of evaporation and absorption, that improvement which consists in utilizing difference in specific gravity of the mixture to cause circulation of the gas with the same vertical direction of flow in said places of evaporation and absorption, and conducting liquid refrigerant to said place or places of evaporation in such a manner that it first reaches a further place of evaporation in contact with the gas where the gas flow is in a vertical direction opposite to that in said place or places of absorption.

4 KGGEL.