US2181528A

US2181528A - Refrigeration

Info

Publication number: US2181528A
Application number: US195715A
Authority: US
Inventors: Widell Nils
Original assignee: Servel Inc
Current assignee: Servel Inc
Priority date: 1937-03-16
Filing date: 1938-03-14
Publication date: 1939-11-28
Anticipated expiration: 1956-11-28

Description

Nbv. 28, 193.9.

N. WIDELL 2.181528 REFRIGERATION Filed March 14, 1938 2 Sheets-Sheet l /l R INVENTOR.

M ATTORNEY.

I N. WIDELL REFRIGERATION Nov. 28, 1939.-

2 Sheets-Sheet 2 Filed March 14, 1938 I INVENTOR; I

M WM 3mm;

MATTORNEY.

Patented Nov. 28, 1939 UNITED STATES 2,181,528 REFRIGERATION Nils Widell, Stockholm, Sweden, assignor, by mesne assignments, to Servel, Inc., New York, 'N. Y., a corporation of Delaware Application March 14, 1938, Serial No. 195,715 In Germany March 16, 1937 23 Claims.

This invention relates to refrigeration, and :more particularly to control of refrigeration systems.

It is an object of the invention to provide an improvement for controlling refrigeration systems, particularly systems of the kind containing ran auxiliary agent or inert gas into which refrigerant evaporates.

This is accomplished by flowing liquid refrigerant to a place of accumulation and conducting liquid therefrom to a. place of evaporation, and removing liquid from the place of accumulation to effect temperature control of the place of evaporation and also to cause abnormal rise of temperature to melt any frost or ice formed at the place of evaporation. In a refrigeration system 'of the kind containing an inert gas, refrigerant fluid may be removed from the place of accumulation by heating and diverted to the gas circuit whereby the flow of gas therein may be reduced .or stopped. 4

'The heating of liquid refrigerant at the place 'of accumulation may be controlled automatically to normally maintain the place of evaporation at a desired low temperature or temperature range. Such normal control may be modified at will to effect defrosting or to increase the refrigerating effect produced at the place of evaporation, as when quick freezing is desired.

The liquid at the place of accumulation may be heated directly or by indirect heat transfer. The heat from a part of the refrigeration system may be utilized to effect indirect heating with the aid of a heat transfer circuit.

The invention, together with .the above and other objects and advantages thereof, will be more fully understood upon reference to the following description and the accompanying drawings forming a part of this specification, and of which:

Fig. 1 illustrates more or less diagrammatically a refrigeration system embodying the invention;

Fig 2 is an enlarged sectional view taken on line 2- 2 of Fig. 1 to illustrate parts of the control more clearly;

Fig. 3 is an enlarged fragmentary sectional view taken on line 33 of Fig. 2; and

, Fig. 4 illustrates more or less diagrammatically a modification of'the invention.

In Fig. 1 the invention is shown embodied in an absorption refrigeration system of a uniform pressure type containing a pressure equalizing gas or auxiliary agent. A system of this type includes a generator I containing a refrigerant in solution in a body of absorption liquid. Although I do not wish to be limited thereto, the refrigerant and absorption liquid may be ammonia and water, respectively. The generator I0 is heated in any suitable manner, as by a burner l I, for example, which projects its flame into the lower end of a flue 12. By heating generator I0, refrigerant vapor is expelled out of solution and flows upward through an air-cooled rectifier l3 and thence into a condenser section Ma of an air-cooled condenser l4.

Refrigerant liquefied in condenser section I la flows into a liquid trap formed by a conduit I5. When sufli'cient liquid accumulates in trap l5, liquid flows through conduit 16 into an upper cooling element l1 and thence through a conduit l8 into a lower cooling element l9. The cooling elements I! and I9 are arranged in a thermally insulated space 20.

Liquid refrigerant in lower cooling element l9 evaporates and diffuses into an inert gas, such as hydrogen, for example, thereby producing a refrigerating effect. The inert gas enters lower cooling element l9 through a conduit 2|. The resulting rich gas mixture of refrigerant and inert gas flows from cooling element l9 through i a vessel 22 into an outer passage 23 of a gas heat exchanger 24.

The upper cooling element I1 is connected by

conduits

25 and 26 to the outer passage 23 of the gas heat exchanger. Liquid refrigerant in upper cooling element I! evaporates and diffuses into 30 rich gas which circulates therethrough, thereby producing a refrigerating effect and precooling liquid flowing to the lower cooling element l9.

Refrigerant vapor not liquefied in condenser section Ma flows from the left-hand leg of trap From the outer passage 23 of gas heat exchang- 4o er' 24 the rich gas mixture flows through a vertical conduit 29 into the lower end of an air-cooled absorber 30. The absorber 30 is diagrammatically shown in the form of a looped coil having a plurality of cooling fins fixed thereto.

- In absorber 30 refrigerant vapor is absorbed by absorption liquid which enters the upper part thereof through a conduit 3|. The hydrogen or inert gas, which is practically insoluble and weak in refrigerant, is returned to the upper part of lower cooling element l9 through a conduit 32,

a plurality of tubes 33 forming an inner passage of the gas heat exchanger, and conduit 2|. The enriched absorption liquid flows from absprber 30 into an accumulation vessel 34.

From vessel enriched liquid flows through a conduit 35 and an inner passage of liquid heat exchanger 36 to a coil 37 which is disposed about the lower end of flue l2. Liquid is raised by vapor-lift action from coil 3? through conduit 38 into the upper part of generator it. Absorption liquid weak in refrigerant flows from the lower part of generator i 6 through conduit 39, the outer passage of liquid heat exchanger 35 and conduit 39 into the upper part of absorber 30.

The lower end of condenser section Mb is connected by vertical conduit Ell, vessel MB, and conduit ii to the gas circuit, as at the gas heat exchanger 2 3, for example, so that any inert gas which may pass into the condenser can flow into the gas circuit.- Refrigerant vapor not liquefied in condenser it flows through conduit 27 to displace inert gas in vessel tit and force such inert gas through conduit M into the gas circuit. By forcing gas into the gas circuit in this manner, the total pressure in the system is raised, whereby an adequate condensing pressure is obtained to insure condensation'of refrigerant vapor in the condenser.

Since gas weak in refrigerant enters lower cooling element 09 through conduit 2| and rich gas flows through upper cooling element H, the gas in the upper cooling element l7 contains a greater amount of refrigerant vapor than the gas in lower cooling element i9. The partial vapor pressure of refrigerant vapor is therefore higher in cooling element l1 than in cooling element l9, and evaporation of liquid takes place at a higher temperature in cooling element l'l than in cooling element l9.

The upper cooling element l9 may be primarily employed for cooling space 20 and is provided with a plurality .of heat transfer fins 42 to increase the effective heat transfer surface. The lower element is is preferably provided with a limited heat transfer surface, and, since evaporation of liquid takes place at a lower temperature therein, it may be employed as a freezing unit.

In accordance with this invention, in order to control the operation of the refrigeration system just described, a heat transfer circuit.is provided for heating liquid refrigerant in trap l5. Although heating of liquid in trap I5 may be effected by any suitable source of heat, it is preferred to utilize heat from a part of the refrigeration system to heat trap 15.

The heat transfer-circuit for transferring heat to trap l5 from a part, such as generator ill, for example, includes an evaporation member 43. The evaporation member 43 is arranged in good heat exchange relation with generator I and is preferably embedded in insulation 44. The

upper end of evaporation member 43 is connected by a conduit 45 to an upper part of a condenser member 46 which is in the form of a jacket disposed about the right-hand leg of trap IS. The lower part of member 46 is connected to a vertical conduit 41 which is connected at its lower end to an accumulation vessel 48. The lower part of vessel 48 is connected by conduit 49 to the lower part of evaporation member 43. A control device 50, which will be described hereinafter, is connected to the lower end of conduit 49.

The evaporation member 43, condenser 46, vessel 48, and connecting conduits form a hermetically sealed circuit which is partly filled with a suitable volatile liquid. The control device 50' controls 'the flow of liquid from vessel 48 and conduit 49 to evaporation member 43-. When the refrigerationsystem is in operation and generator iii is being heated, liquid in evaporation member Aid is heated and evaporated. The vapors pass upwardly through conduit :35 into condenser member 46. The vapor is condensed in member at and flows downward through conduit fill, vessel as, and conduit 49 into the lower part of evaporation member N where it is again evap" orated. The volatile fluid circulates naturally in the manner just described and serves as a heat transfer agent. The evaporation of liquid in member t3 takes up heat from generator iii, and the condensation of the vapors in Jacket or member as gives up heat to liquid in trap in.

As will be seen in Fig. 1, the right hand leg of trap i is connected by a conduit 5i to conduit 32 through which gas weak in refrigerant flows from absorber 30 to lower cooling element l9. When liquid refrigerant is heated in trap l5, therefore, the refrigerant vapor produced by such heating as well as liquid refrigerant can flow into the gas circuit.

The control device 50 for controlling the heat transfer circuit includes a casing 52 having bosses 53 and 53' which form inlet and outlet openings, respectively, for the volatile liquid. As shown in Fig. 2, liquid flows from the inlet opening at boss 53 past a valve 54 and thence to the outlet opening at boss 53'. The valve is provided with a stem 55 which extends through an opening in casing 52 and is secured at its outer end to a plate 56. To raised shoulders formed on plate 56 and casing 52 are secured the opposite ends of an expansible and contractible bellows 51, whereby the volatile fluid circuit is effectively sealed. The valve 54 is urged to its closed position by a coil spring 58 which is disposed between the end of casing 52 and a flange at the periphery of plate 56.

The opposite end of control device 5% includes a casing 59 having an annular member 60 secured to the inner end thereof. To the annular member 60 is secured one end of a bellows 6! which in turn is secured at its other end to a plate 52. Between the annular mennber 69 and plate 52 is disposed a coil spring 63 tending to expand the bellows 6|. The plate 62 is formed with a hollow cylindrical portion which extends toward the annular member 60. To the outer end of the cylindrical portion is threadedly secured a stud or cap screw 64. V

The casings 52 and 59 are secured to the opposite ends'of a cylindrical sleeve 65 having diametrically opposite openings 66. A shaft 5? having a handle 68 extends through the openings 66 in sleeve 65. To shaft 61 is fixed a cylindrical member 69 having a cam ID of the shape shown in Fig. 3.

When handle 68 is turned so that cam m is in the position shown in Fig. 3, movements of bellows 6| will be transmitted through the cam to plate 56, whereby automatic control of valve 54 is effected, as will be described hereinafter. When cam is moved so that the radius Y is moved to the line XX, no movements of bellows 6| will be transmitted to plate 56 and valve 54 will remain closed all of the time by action of spring 58. When cam member 69 is turned so that the radius Z is moved to the line X-X, valve 54 will open and remain open independent of any movements of bellows 6| To the closed end of casing 59 is connected one end of aconduit H which is connected at its other end to a thermal bulb 12. The thermal bulb 12 is arranged in good thermal contact with vessel 22 which may be considered a part of lower cooling a refrigerating effect.

element Ill. The bulb I2, conduit H, and space 13 defined by casing 59 and bellows 6| constitute an expansible thermostat which may be filled with water or other suitable freezing solution. When the solution freezes due to a decrease in temperature of cooling element IS, the expansion of the frozen solution causes contraction of bellows 6|. Conversely, when the frozen solution melts due to an increase in temperature of cooling element l9, the solution contracts and bellows 6| expands by action of spring 63.

During normal operation, the refrigerant fluid, inert gas, and absorption liquid circulate in the refrigeration system in the manner described above whereby cooling elements I! and I9 produce With normal operation. hydrogen or inert gas circulates continuously in the gas circuit including the cooling element l9 and absorber 30. This circulation of hydrogen or inert gas is due to the difference in specific weight of the rich mixture of inert gas and vaporous refrigerant in cooling element l9, outer passage 23 of gas heat exchanger 24, and vertical conduit 29; and the weak mixture of these gases in absorber 30, conduit 32, inner passage 33 of the gas heat exchanger, and conduit 2|. Due to the difference in specific weight of the columns of rich and weak gas, therefore, a force is developed in the gas circuit for causing flow of rich gas toward absorber 30 and flow of weak gas toward cooling element l9. Similarly, due to the difference in specific weight of rich gas in conduit 25 and richer gas in cooling element l1 and conduit 26, a force is developed for causing flow of gas in'the local circuit including upper cooling element l9.

The above normal operation of the refrigeration system takes place when valve 54 of control device 50 is closed and no heat is transferred from generator II] to trap l by the closed'heat transfer circuit. When valve 54 is opened, however, volatile liquid is permitted to fiow from -vessel 48- and conduit 49 to evaporation member 43, whereby heat is transferred from generator ill to jacket 46, as explained above, to cause heating and evaporation of liquid in trap l5. Liquid in the right-handleg of trap I5 is raised by vapor-lift action due to the vapor bubbles formed therein, whereby the raised liquid overflows through conduit 5| into conduit 32. With liquid flowing from trap l5 through conduit 5|, the liquid level in trap I5 is lowered. Under these conditions refrigerant vapor liquefied in condenser section |4a flows into the trap, and, since the liquid level therein is lowered, no flow of liquid into cooling elements l1 and I9 through conduit 16 will take place.

If desired, all of the liquid in trap I5 may be removed to bring about a reduction in the production of cold by space cooling element II. It usually is not necessary to remove all of the liquid from trap l5, however, and this is particularly true in a refrigeration system containing an auxiliary medium or inert gas. Sufficient heating of trap I5 is effected where the amount of liquid over-flowing through conduit 5| into conduit 32 is effective to reduce or stop the circulation of gas in the gas circuit. The

liquid flowing into conduit 32 from trap l5 evaporates and diffuses into weak gas flowingfrom absorber 30 to lower cooling element l9. This increases the specific weight of the column of weak gas in the gas circuit and reduces the difference in specific weight of the columns of rich and weak gas, whereby the force normally developed for circulation of gas in the gas circuit is reduced. When the flow of weak gas into cooling element I9 is reduced or stopped, evaporation of refrigerant takes place at a higher temperature or no evaporation may take place due to the higher partial pressure of refrigerant vapor. With no flow of liquid into upper cooling element I1 and the circulation of gas in the gas circuit reduced or stopped, therefore,

' less cold is produced by cooling elements l1 and l9 and the temperatures of these cooling elecharacter shown is desirable inasmuch as control of the refrigeration system may be effected without the necessity of reducing or shutting off the energy supply. This is particularly advantageous in that the production of cold may be immediately instigated when normal opera- ,tion is' resumed after a modified period of operation during which the production of cold is reduced.

The control device 50 may be adjusted to maintain storage space 20 substantially at a constant temperature or temperature range or to effect defrosting. When storage space 20 is to be maintained at a desired low temperature or temperature range, handle 68 is turned so that cam is in the position shown in Fig. 3. With cam member 10 in this position, movements of bellows 6| will be transmitted through the cam to valve 54. The freezing solution in the expansible thermostat will freeze and expand when cooling element l9 tends to fall below a desired low temperature which is the freezing decrease the rate of flow of liquid refrigerant through conduit l6 into cooling elements I1 and I9, and also reduce the circulation of gas in the gas circuit. When this occurs, the refrigerating effect produced by cooling elements l'l and I9 will be reduced.

Conversely, when space 20 tends to rise above the desired low temperature or temperature range which is above the freezing temperature of the solution in the expansible thermostat, the frozen solution will melt. With melting of the frozen solution and consequent contraction thereof, bellows 6| will expand due to the action of spring 63. This permits valve 54 to close due to action of spring 58, thereby shutting off the flow of volatile liquid into evaporation member 43. Under these conditions heating of trap I5 is no longer effected and the refrigerating efiect produced by cooling elements l1 and I9 will be increased. I

When it is desired to effect defrosting, handle 68 of control device 50 is turned so that radius 5 Z in Fig. 3 is moved to the line X-X. When this is done shaft6l is moved to one end of the elongated openings 66 and cam 10 is effective to open valve 54. Valve 54 will remain open independent of the expansible thermostat and 10 heat will be transferred from generator Iil to trap l5. With heating of liquid in trap l5 the production of cold by cooling elements l1 and I!) will be reduced. This will permit the temperatures of cooling elements l1 and I9 to rise, 15 so that frost accumulated thereon will melt. When defrosting is completed, handle 68 may again be turned so that automatic control of the refrigeration system may be resumed in response to the temperature of lower cooling elego ment I9. I

When it is desired to modify the normal automatic control and prevent heating of trap l5 so that the refrigerating eflect produced by cooling elements I! and I9 will be at a maximum,

25 handle 68 may be turned so that radius Y will be moved to the line X-X. In this position cam I is ineffective to open valve 54 by itself and also ineffective to transmit movements of bellows 6| to valve 54. The valve 54 will therefore 30 remain closed all of the time and the refrigerating effect produced by cooling elements l1 and I9 will be at a maximum. The normal automatic control of the refrigeration system is modified in this manner when the maximum 35 production of cold is desired, as when quick freezing of ice and other frozen matter is necessary. Instead of locating the heating. jacket 46 about the right-hand leg of the trap l5, the heating jacket may be arranged about the trap in such a manner that. liquid is also raised in the left-hand leg of the trap when the latter is heated. In such case only a part of the liquid flows from trap l through conduit 5| when heating of the trap is effected, and the remaining liquid flows from the trap through conduit 56 or through both conduits i 6 and 21 into the cooling elements. Since the circulation of gas in the gas circuit is reduced and may be completely stopped when such liquid enters the cooling elements, normal evaporation of liquid in the cooling elements will not take place.

The lower cooling element 59 may be provided with inserts I4 so that shallow pools of liquid refrigerant may be maintained in the entire lower cooling element; In addition, the vessel 22 is connected in series relation with lower cooling element 69 so that unevaporated liquid may be accumulated therein. When heating of trap i5 is stopped and normal operation of the refrigeration system is resumed, the gas circulates in the gas circuit and the liquid in vessel 22 is immediately available for the production of cold. If trays containing water to be frozen are inserted into the lower cooling element is, for example, the load on the cooling element is temporarily increased. Due to this temporary increase in load, more liquid refrigerant can evaporate and diffuse into inert gas. By providing vessel 22 liquid refrigerant is immediately available in the freezing unit to take care of the temporary increase in load.

Since generator ill may be heated continuously with the type of control provided, th amount of liquid refrigerant that may be accumulated in vessel 22 is preferably .z -er so that circulation of liquid will always take place in the liquid circuit including generator l0, liquid heat exchanger 36, and absorber 30. In other words, during operation the liquid level in generator ID will always be above the upper end of conduit 3! so that liquid will flow from generator [0 to the upper part of absorber 30.

The vessel 22 is provided with baiiies 15 and 16 having openings I1 and 18 in the top and bottom parts thereof, as shown in Fig. 1. At the lefthand end of vessel 22 is provided an overflow conduit 19 having its lower end connected to the nected to conduit 80 at approximately the same height as the openings 11 in bailles 15.

If the 'vessel 22 should contain absorption solution, unevaporated liquid flowing into the right-hand pocket of vessel 22 settles upon top of the absorption solution and presses the latter into the second smaller pocket through the bottom opening 18 in the first baiile 16. This raises sorption solution flows into the next larger pocket. In this manner any absorption solution in vessel 22 is moved from the right to the left therein and thence into conduit 80, whereby the vessel is purged of absorption solution.

In Fig. 4 is illustrated a modification of the invention. The refrigeration system in Fig. 4 is similar to that illustrated in Fig. 1 and differs therefrom in that it includes only a single condenser l4 and a single cooling element IT. The remaining parts of the system are the same as in Fig. 1 and designated by the same reference numerals. In Fig. 4 liquid refrigerant flows from condenser l4 into a gas separating chamber 8| and thence through conduit l6 into the upper part of cooling element I l. Conduit i6 is U- shaped to form a liquid trap and the lower part thereof is in heat exchange relation with the outer passage of the gas heat exchanger 24.

Gas weak in refrigerant fiowsfrom the inner passage of gas heat exchanger 24 through conduit 2i into the upper part of cooling element H. The resulting rich gas mixture of refrigerant and inert gas flows from the lower part of the cooling element through conduit 82 into the outer passage of gas heat exchanger 26, and thence through vertical conduit 29 into the lower part of absorber St.

A vent conduit 83 is connected to the chamber 8i and to the gas circuit, as at the gas heat exchanger 25, for example. The vent conduit 83 extends upward from chamber Bi and then downwardly to the gas heat exchanger, so that any gas which passes through the condenser It can flow into the gas circuit and not be trapped in the condenser.

The condenser member 46' of the heat transfer circuit is arranged in good heat exchange relation with conduit it. If desired, the condenser member 6% and the portion of conduit E6 in contact therewith may be embedded in insulation.

When control device til is operated either manually or automatically in response to the expanlower part of the vessel and its upper end consible thermostat to permit liquid to flow from conduit 49 to evaporation member 43, heat is transferred from generator III to condenser member 46. The liquid in conduit I6 is heated and evaporated, and due to the forming of vapor bubbles, liquid is raised by vapor-lift action in the right-hand part of conduit IS. The liquid is raised through chamber BI and vent conduit 83 into the gas circuit. In this manner refrigerant in liquid or vapor form may be caused to flow from conduit 16 to the portion of the gas circuit through which weak gas flows from absorber 30 to cooling element II.

The volatile liquid employed in the heat transfer circuit preferably possesses such physical properties that a low pressure will prevail in the circuit for the temperature existing therein. The circuit is preferably evacuated before it is charged with the volatile liquid. If desired, the circuit may be charged with a gas in addition to the volatile liquid so that evaporation of liquid in the evaporation member will take place at a desired temperature. Instead of employing a volatile liquid, the heat transfer circuit may be filled with a liquid which remains in 'a liquid state. In such case natural circulation of liquid is effected due to differences in specific gravity of the liquid in different portions of the circuit.

Although several embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that various modifications and changes may be made without departing from the spirit and scope of the invention. While the improved control is particularly adapted for refrigeration systems in which energy is supplied thereto continuously, the control may also be employed in other types of refrigeration systems, as pointed out above. It is therefore contemplated to cover all modifications and changes-which come within the spirit of the invention, as pointed out in the following claims.

What is claimed is:

1. In the art of refrigeration employing a system using inert gas into which liquid refrigerant evaporates at a place of evaporation, the improvement which consists in collecting liquid refrigerant at a place of accumulation and conducting liquid therefrom to the place of evaporation, and removing refrigerant fluid from the place of accumulation toa place in the system other than the place of evaporation to interfere with the evaporation of liquid refrigerant in the place of evaporation.

2. In a refrigeration system, the improvement which consists in flowing liquid refrigerant to a place of accumulation and conducting liquid therefrom to a place of evaporation when liquid is at or above a predetermined level at the place of accumulation, and flowing refrigerant from the place of accumulation to a place in the system other than the place of evaporation to lower the liquid at the place of accumulation below the predetermined level to stop the flow of refrigerant to the place of evaporation.

3. In the art of refrigeration in which evaporation of liquid refrigerant takes place in the presence of an inert gas at a place of evaporation,

inert gas enriched with refrigerant vapor flows from the place of evaporation to a place of absorption, and inert gas weak in refrigerant vapor flows from the place of absorption to the place of evaporation, the flow of gas being due to the difference in specific weight of columns of inert gas enriched with refrigerant vapor and weal: in

refrigerant vapor, the improvement which consists in flowing liquid refrigerant fluid into the column of gas weak in refrigerant at a place other than the place of evaporation to reduce the flow of gas between the place of evaporation and the place of absorption.

4. In a refrigeration system, the improvement which consists in flowing liquid refrigerant to a place of accumulation and conducting liquid therefrom to a place of evaporation, and heating 1 a heat transfer fluid by a part of the system and flowing the fluid from such part in heat transfer relation with the place of accumulation to heat liquid therein and cause flow of refrigerant therefrom to a place in the system other than the place of evaporation to interfere with evaporation of liquid refrigerant in the place of evaporation.

5. An absorption refrigeration system including a cooling element and an absorber connected to form a gas circuit for circulating gas therein by a force developed by the difierence in specific weight of columns of gaseous fluid, a member to conduct liquid refrigerant to said cooling element, and conduit means to conduct refrigerant from said member to a part of the gas circuit other than the cooling element to reduce the force developed in the gas circuit for circulating gas therein.

6. A refrigeration system including a heated part and a cooling element, a member to conduct liquid refrigerant to said cooling element, conduit tion of volatile fluid in said vaporization-condensation circuit.

8. A refrigeration system as defined in claim 6 and including means responsive to a temperature condition affected by said cooling element for controlling flow of volatile fluid in said vaporization-condensation circuit.

9. An absorption refrigeration system of an inert gas type comprising inter-connected parts including a gas circuit having a cooling element into which liquid refrigerant is conducted for evaporation in the presence of the inert gas to produce a refrigerating effect, such cooling element being subject to formation of frost or ice, means including a liquid trap connected in said system to cause flow of hot vaporous fluid into said gas circuit when liquid is removed from said trap, so that the temperature of said cooling element is raised sufficiently to melt frost or ice, and heat transfer structure comprising a closed fluid circuit containing a heat transfer fluid and having one part associated with a source of heat and another part associated with said trap for transferring heat from the source of heat to the trap to remove'liquid from the latter by heating.

10. The combination set forth in claim 9 and including means to controltransfer of heat to said trap by said heat transfer structure.

11. The combination set forth in claim 9 in which a part of the system serves as the source of heat.

12. The combination set forth in claim 9 in which the closed fluid circuit'contains a volatile fluid and in which said one partconstitutes a vaporization portion and said other part constitutes a condensation portion of a vaporizaticm condensation system.

13. An absorption refrigeration system of an inert gas type including a cooling element, a member for conducting liquid refrigerant to said cooling element for evaporation therein in the presence of inert gas to produce a refrigerating effect during normal operation of the system, such cooling element being subject to formation of frost or ice, means including a liquid trap to cause an increase in partial pressure of refrigerant vapor in said cooling element when liquid is removed from said trap, so that the temperature of said cooling element is raised sufficiently to cause melting of frost or ice, and said trap being so connected and arranged in said system that, when liquid is removed therefrom to cause an increase in partial pressure of refrigerant vapor in said cooling element, liquid is also conducted from said trap to said cooling element, said cooling element having sufficient capacity to hold liquid conducted thereto from said trap whereby such liquid is immediately available to produce a refrigerating effect when liquid is permitted to remain in said trap and normal operation of the system is resumed.

14. An absorption refrigeration system of an inert gas type comprising a plurality of parts and having a gas circuit including a cooling element subject to formation of frost or ice and into which liquid refrigerant is conducted for evaporation therein in the presence of inert gas to pro-.

duce a refrigerating effect, one of said parts being arranged to hold liquid and being connected in said system to cause flow of hot vaporous fluid into said gas circuit when liquid is removed therefrom, and means responsive only to a temperature condition affected by said cooling element to cause removal of liquid from said one part.

15. In a refrigeration system having an inert gas circuit including a place of evaporation subject to formation liquid refrigerant of frost or ice and in which evaporates in the presence of inert gas to produce a refrigerating effect, the improvement which consists in collecting liquid refrigerant at a place of accumulation, removing refrigerant fluid from the place of accumulation to the gas circuit to increase the partial pressure of refrigerant vapor in the place of evaporation to raise its temperature sufiiciently to melt frost or ice, and also simultaneously removing refrigerant fluid from the place of accumulation to the place of evaporation for retention therein, whereby such refrigerant fluid is available to produce a refrigerating effect when refrigerant fluid is permitted to collect at the place of accumulation.

16. In a refrigeration system having a place of evaporation subject to formation of frost or ice and in which liquid refrigerant evaporates in the presence of an inert gas in a place of evaporation to produce a refrigerating efiect, the improvement which consists in collecting liquid at a place of accumulation, removing liquid from the place of accumulation to effect an increase in the partial pressure of refrigerant vapor in the place of evaporation and cause the temperature of the place of evaporation to rise sumciently to melt frost or ice formed thereon, heating a heat the place of accumulation to cause removal of liquid therefrom, and flowing heat transfer fluid from the region back to the place of heating.

17. The improvement as set forth in claim 16 in which the place of heating is associated with a heated part of the refrigeration system.

18. The improvement as set forth in claim 16 in which the heat transfer fluid is vaporized at the place of heating and condensed at the region in thermal exchange relation with the place of accumulation.

19. The improvement set forth in claim 16 in which heat transfer fluid is vaporized at the place of heating and condensed at the region in thermal exchange relation, with the place of accumulation, and controlling flow of the heat transfer fluid to regulate the transfer of heat to the place of accumulation from the place of heating.

20. In a refrigeration system having a place of evaporation subject to formation of frost or ice and in which liquid refrigerant evaporates inthe presence of an inert gas in a place of evaporation to produce a refrigerating effect, the improvement which consists in collecting liquid at a place of accumulation, removing liquid from the place of accumulation to effect an increase in the partial pressure of refrigerant vapor in the place of evaporation and cause the temperature of the place of evaporation to rise sufliciently to melt frost or ice formed thereon, heating a heat transfer fluid at a place of heating removed from the place of accumulation, flowing such heat transfer fluid from the place of heating to a region in thermal exchange relation with the place of accumulation whereby heat is transferred to the place of accumulation to cause removal of liquid therefrom, flowing heat transfer fluid from the region back to the place of heating, and controlling transfer of heat by the heat transfer fluid.

21. In a refrigeration system having a place of evaporation subject to formation of frost or ice and in which liquid refrigerant evaporates in the presence of an inert gas in a place of evaporation to produce a refrigerating effect, the improvement which consists in collecting liquid at a place of accumulation, removing liquid from the place of accumulation to effect an increase in the partial pressure of refrigerant vapor in the place of evaporation and cause the temperature of the place of evaporation to rise sufiiclently to melt frost or ice formed thereon, heating a heat transfer fluid at a place of heating removed from the place of accumulation, flowing such heat transfer fluid from the place of heating to a region in thermal exchange relation with the place of accumulation whereby heat is transferred to the place of accumulation to cause removal of liquid therefrom, flowing heat transfer fluid from the region back to the place of heating, and controlling transfer of heat by the heat transfer fluid in accordance with changes in a temperature condition afiected by the place of evaporation.

22. The improvement as set forth in claim 21 in which the place of heating is associated with a heated part of the refrigeration system.

23. The improvement as set forth in claim 21 in which the 'heat transfer fluid is vaporized at the place of heating and condensed at the region in thermal exchange relation with the place of accumulation, and controlling flow of the heat transfer fluid to regulate the transfer of heat to the place of accumulation from the place of heating.