US2448454A - Refrigerating system - Google Patents

Description

Aug. 31, 1948. G. MUFFLY 2,448,454

l REFRIGRATING SYSTEM original Filed April 5, 1934 2 sheets-Sheet 1 I im;

INVENTOR. Gle??? Mznfflry.

Aug. 31, 1948. G. Mul-'FLY i REFRIGERATING SYSTEM Original Filed April 5, 1934 l 2 Shets-Sheet 2 INVENTOR. GZenr? Maf'ly,

BY TORNEYS.

Patented Aug. 31, 194s' l REFRGERATING SYSTEM Glenn Mumy, springfield, ohio Application January 23, 1939, serial No. which is a division of application 252,292, Serial No.

719,099, April 5, 1934. Divided and this application February v,

l 5 Claims. This application is a division of co-pending application Serial No. 252,292, filed January 23, 1939, now Patent No. 2,368,675, issued February 2, 1945, which is a division of application Serial No. 719,099, filed April 5, 1934, now Patent No. 2,145,774, issued January 31, 1939. This invention relates to refrigerating mechanism and the claims of the co-pending application referred to are particularly directed to a new and novel method of producing ice and controlling the operation of the mechanism during such production.

Objects of this invention include the provision of an improved valve mechanism for controlling the iiow of refrigerant; the provision of a valve lmechanism for controlling the flow of refrigerant in which the pressure of the liquid refrigerant is employed to actuate the valv the provision of a method and apparatus for refrigerating by means of mechanism so `constructed 'and arranged as to provide an operating cycle which does notl dump liquid refrigerant into the suction passage of the mechanism.

Another object is to provide two evaporators which are selectively refrigerated and which are separated by insulation.

Another object is to provide in acontrol device means for displacing liquid `by heating one portion of an enclosure partially iilled with a volatile liquid for the purpose of causing the liquid to condense inanother portion of the en closure, thereby shifting the zone of temperature response. y

Another object is the provision againsta rush of liquid refrigerant into the suction line at a time that evaporative effect is shifted from one evaporator to another.

The above being among the objects of the present invention, the same consists in certain novel features of construction, combinations of parts, and methods of control and operation, to be hereinafter described with reference to the accompanying drawings, and then claimed, having the above and other -objects in view.

In the accompanying drawings which illustrate suitable embodiments of the present invention and in which like numerals refer to like parts throughout the several different views, V

Fig. 1 is a more or less diagrammatic, broken, partially sectioned view of a refrigerating ap- 1945, Serial N0. 576,182

`the path of refrigerant through the various evaporator units and the capillary tube of Fig. 3;

Fig. 5 is a horizontal sectional View taken through one of the evaporatorunits of Fig. 3 as on the linc`5-5 of Fig. 3; and

Fig. 6 is a fragmentary sectional view taken'v on the line B--S of Fig; 3.

It will be readily understood by those skilled in the art that certain of the methods and apparatus herein disclosed are applicable for uses other than the production of ice, but the originals of this application, now Patent No. 2,145,- '774 and copending application Serial No. 252,292. which is now Patent No. 2,368,675, deal princlpally with the artificial production of ice, hence the description and explanation herein, primarily for the purpose of illustration, show mainly the application of such methods and/or'apparatus to their use in the artificial production of ice.

In my previous application -which resulted in Patent No. 2,145,773 and in the above mentioned parent applications of this one. means are disclosed for the production of ice by artificial refrigeration and they include, in certain of the modifications there shown, a refrigeratingmechanism. including a compressor, condenser and receiver constituting a refrigeranthlgh side, a.'

water tank the bottom of which has associated therewith certain surfaces which, for the simplicity of explanation, will be referred to as cupsor cones, exposed to thewater within the tank,

and each of which has associated with its unwetted surface an evaporating element or refrigerant lowsde element for the purpose of refrigerating it, The evaporators may be connected in series or in parallel. or, as herein describe-d, in a combination of both with the compressor and condenser. .Suitable control means paratus 'embodying an improved refrigerant flow' are provided ln the connection between the high and low sides and between certain series or groups of the cups or cones so that one set or group of cups or cones will be refrigerated so as to cause ice to be formed or on the same, while the other grou-p of cups or cones -will be warmed in order to cause masses of ice previously formed in oren4 the cups or cones of such group to be melted loose therefrom whereby their natural There is illustrated in Fig. 1 a refrlgerating mechanism including a high side indicated generally at I0, a low side indicated generally at I2 and a control mechanism indicated generally at II. The high side includes the usual motor I driven compressor 12, condenser 13 and receiver 14. Th-e low side includes two groups of evaporating units in the form of rings 3| connected in series through the dual expansion valve 36, each serif.` beingsubdivided intotwo smaller groups the individual rings of which are connected in parallel. Each ring 3| of the groups 21 and 28 of rings 3| is thermally associated with a corresponding ice making surface arranged in a water tank 9, the groups 21 and 28 preferably being arranged at opposite ends of the tank 9 or otherwise spaced apart to minimize heat transfer between them. The control unit II includes suitable valves for controlling the direction of flow of refrigerant from the high side I6 to the low side I2 together with thermal responsive means in the form of bellows 63 and 64, the entire control unit being such that the direction of flow of refrigerant through the low side I2 may be periodically reversed.

Any refrigerant may be employed in connection with this refrigerating system, but it is preferable to use one having a high ratio of specific heat of liquid to latent heat of vaporization, such as dichlorodifluoromethane, for instance, so that ample heat is available for melting the ice free from the refrigerated surfaces.

It will also be understood that any desired and/or conventional form of control means may be employed in connection with the refrigerating system as a whole for effecting cyclic operation of the system, where such cyclic operation, or starting and stopping, of the system'is desired.

The valve assembly |I is connected with the evaporator assembly I2 by means of two tubes I3 and I4, which act alternately as liquid and vapor passages. Liquid refrigerant is introduced through tube I5 to the tubes I6 an-d I1, but in the position of valves as shown it must flow through tube I6 and port I8, since port I9 is closed by valve 2| while valve 20, controlling port I8, is lifted from its seat by guide 22 of piston 24. It will be noted that the corresponding guide 23 of piston 24 has receded from the valve 2|, allowing it to close under the action of spring 25, whilev spring 26 of valve 20 is compressed.

After passing through the port I8 the liquid refrigerant, which is still warm and under, high pressure, passes through tube I4 to the right hand section 28 of evaporator I2, where it flrst enters the tubular passage 30, connected in manifold to the evaporator rings 3| of section 28,

thence the warm liquid passes through the various evaporator rings 3|, but it does not evaporate on account of the fact that it is still under high pressure. The warm liquid serves to heat these rings 3| in section 28 of the evaporator, and then passes through tubes 32 and 34 tothe expansion valve 36, which is of a dual type as shown in more detail in Fig. 2.

Continuing to trace the refrigerant flow through the expansion valve in Fig. 2, it will be noted that the liquid refrigerant enters' the chamber 31, surrounding the bellows 39, which bellows is compressed by the high pressure of the refrigerant so that the valve 4I is closed by the spring 43. The liquid therefor passes through port 46 to chamber 38. The port 46 is opened by valve 42 during this period of operation because the bellows 46 is surrounded by low pressure refrigerant and the bellows expands under action of an internal spring similar to spring 41 in bellows 39, compressing spring 44 and lifting valve 42 from its seat. The action of bellows 40, spring 44 and valve 42 are the same as in an ordinary expansion valve, so need not bc described here in detail. Bellows 39, spring 43 and valve 4| are in effect inoperative at this time,

since the bellows is compressed and thevalve remains closed, so the action is thev same as if an ordinary expansion valve were used with provision for flow in a single direction. It may be noted in passing, however, that it isv preferable to employ a small tube such as 52 to connect and thereby equalize the pressure in the interior of the bellows 39 and 40.

The refrigerant, which is now at low pressure, leaves chamber I38 through tube 35 and continuance of its flow may be traced in Fig. l. Passing through tube 35 and tubes 33 the low pressure refrigerant now enters evaporator rings 3| in section'21 of the evaporator I2, where it evaporates, picking up heat from the walls of the rings 3| in such section. It will be understood that the heat comes from water in a tank having areas in contact with these evaporator rings 3|, as shown in Fig. 3, for instance, thus causing the water to freeze in the tank adjacent to the evaporator rings.

The vaporized refrigerant then passes through tubes 29 and I3 to the valve assembly II, where it is free to pass the guide 23 of piston 24 on account of this guide being provided with longitudinal flutes 54y and it then passes through cylinder bore 55, from which the piston 24 is slightly withdrawn, into chamber 6I surrounding bellows 63, thence partially through port 65 of wall 66 in housing 61 and out through passage 68 and tube 69 through an additional evaporator 10 to suction tube 1I. The vaporized refrigerant is then compressed by compressor 12, condensed in condenser 13, collected as liquid in receiver 14 and returned as warm liquid under high pressure through tube 15 leading to tube I5, where it repeats the circuit as described.

This operation continues until the desired thickness of ice is formed on the wall surfaces of the water tank adjacent to the evaporator rings 3| of evaporator section 21. With the reduction of heat transfer rate resulting from such formation of ice the refrigerant temperature in tube I3'and cham-ber 6| drops, cooling the bellows 63 and the volatile fluid 16 contained therein, reducing its vapor pressure within the b ellows until the bellows 63 contracts under the action of the higher vapor pressure of fluid 16 in the warmer bellows 64. The bellows 64 is warmer because it is not directly in the path of the cold refrigerant, being contained in a substantially dead vapor body in chamber 62. As the internal pressure in bellows 64 overcomes the pressure in bellows 63 the rod 19 moves to the left, compressing bellows 63.

The springs 11 and 18 in these two bellows may be omitted, but are shown as almeans of obtaining adjustment. By removing the plugs covering the screws 80 and 8| they may be adjusted'inwardly to push the bellows heads 82 and 88 closer .together thereby putting more compression on springs 11 and 18; adjusted outward to reduce such compression; or one screw adjusted inward and one outward to shift .the normal position of rod 19 and the bellows heads 84 and 85 to which rod 19 is attached. In this manner the' action of the two bellows may be balanced, cycles shortened or prolonged, etc., as will be understood from the following description of how the bellowsact to control the operation of valves.

Returning now to the description of the bellows operation due tothe cooling of bellows 63 while bellows 64 remains at a constant temperature or is warmed by its isolation from the coldrefrigerant and its proximity to the warm liquid, it will be understood that the bellows head 85..and bellows head 84 are both moved to the left and that head 84 will move the arm 86 clockwise about its pivot |00, pulling the toggle link 88 downward and the stop 90 away from the wall 66, and stretching the spring 92. The result of this movement is to move the pin |82 and the toggle link 96 dow-nward until the center of |02 isbelow the straight line between pin and pin 98. The toggle formed by links 88 and 96 has been in locked position, Where it was held by spring 92, which in this position has a considerable leverage over the corresponding spring 93 on the other side. However, as soon as the right hand toggle moves out of its locked position the piston 24 is moved to the left by the high pressure liquid in passage |04.

As soon as this liquid .pressure has unseated valve 58 from seat 60the high pressure liquid acts upon the full area of piston 24 in cylinder 56,

carrying the piston and the two toggle mecha-l nisms past the point where spring 93 obtains an increasing leverage advantage over spring 92.

Meanwhile the movement of piston 24 to the leftv has allowed valve 20 to seat, closing its port I8 and stopping the flow of liquid through tube I6. Simultaneously the left end of piston 24 has entered cylinder 55 where it encounters only low pressure vapor. The piston is guided into its cylinder by the iiuted guide 23, which ts freely in passage of the valve body I 01. At the final movement of piston 24 to thc left. when the spring 93 is in position to exert a forcible thrust on piston 24 through the toggle links 89 and 91 and the-pin 99, the guide 23 strikes the stem of valve 2 I, causing this valve to open against the pressure of liquid refrigerant in tube I7. The left hand toggle then locks itself with pin |03 just over center and stop 9| in contact with wall 66. y'

This movementl of the parts leaves valve closed, valve` 58 and cylinder 56 open, valve 51 closed, and valve 2| open. The refrigerant ow is thus reversed in the part of the system affected, so that liquid flows through tubes I1, I3 and 29 to the evaporator units or rings 3| of section 21, thence through passages 33 and 35 to the expansion Valve 36. From the expansion valve the low pressure refrigerant flows through passages 34 and 32 to the evaporator units or rings 3| in section 28, where a considerable part of it evaporates, and it then flows through passages and I4 to passage l|04, and cut through cylinder 56 into chamber 62, where'it acts to cool bellows 64 and prepare for another reversal of operation.

At the time that piston 24 is Withdrawn from cylinder 56 in the -movement thus described, it will be seen thatthe liquid contained in evaporator section 28 is released to flow into chamber 62 and thence through passage 68 to the second evaporator 10, which is thus fed periodically with liquid refrigerant in addition to that which reaches it more slowly during the balance of the cycle. The evaporator 10 is accordingly designed to accommodate such fluctuations in its liquid refrigerant content by providing it with ample internal volume.

While liquid is passing from the comparatively warm evaporator section 28 to chamber 62 there is a sudden increase of pressure in both chambers 6| and 62, which would cause both bellows to contract if it were not for the facts that they are tied together by the rod 19 and that each contains a rather stiff spring, 11 in 68 and 'I8 in 64. The warm liquid will at first tend to expandbellows 64, which does no harm, but care must be used in the design of the case 61 to insure against liquid trapping around the bellows, as it would then boil ofi slowly and refrigerate the bellows to a point that might cause a premature` reversal of the valves. It should be remembered that pressure alone (within the working range) will not compress either bellows because they are tied together, hence the analysis of bellows action is based on temperature, and while the liquid is momentarily raising the pressure in chambers 6I and 62 it is also raising the temperature to something above that of the bellows 63 at the time its contraction causes themechanism to trip and reverse the valves.

Referring again to Fig. 2 and tracing the action of the reversible expansion valve 36, we find that after the valve reversal as described the liquid refrigerant entered the chamber 38 through passage 35. This will cause bellows 40 to contract under pressure, which contraction is stopped before it damages the bellows by means of a sleeve similar to |08 in bellows 39. This sleeve acts as a guide to keep the bellows i-n line with the valve, as a stop against undue compression in bellows length, and as a stop against damage toconvolutions due to pressure exerted on side walls externally.

The valve bodies |06 and |01 are attached to the housing 61 by means of studs or screws (not shown) and are made gas-tight by means of suitable gasket rings which are shown. These gaskets also serve to break the metallic conductivity of heat so that very little of the heat of the warm liquid refrigerant will be lost by conductivity to the cold body 81. It will also vbe found advisable to insulate the tubes I3, I4, |5, I6 andl'l as Well `as valve bodies |06 and |01 from cold airas iny and gasket. Tapped lugs are shown for securing such a cover or covers.

Parts 86 to 91 inclusive and |00 to |03 inclusive may be duplicated, one set on either side of piston 24, as indicated ,by part 89 which is broken to lshow two similarparts of the same number. Pins 98 and 89 would each pivot two side members to the piston 24 in that event. l

Referring to Fig. 3 it will be understood that vaporized refrigerant passing through the tube 1| is compressed by the compressor 12, condensed in the condenser 13 and-collected as liquid in the receiver 14, from which the liquid refrigerant passes through the tube 15 which enters the refrigerated space enclosed within the insulated wall 402. After passing through this insulated wall the tube 15 is enclosed by thermal insulation as indicated by broken line 403.

Liquid refrigerant is conducted by the tube 15 to the coils 404 and 405 surrounding the bellows chambers 406 and 401, respectively, and then through tubes 408 and 409 to the interiors of liquid valve housings 4|0 and 4| I. The liquid refrigerant is stopped in housing 4|| by the valve 4|3 which is shown closed in this view, while the corresponding valve 4| 2 on the right-hand side is open, allowing liquid refrigerant to pass through the passages formed by the utes in the stem of the valve 4|2 into the chamber 4| 6 and tube 4|8 leading to the interior of valve housing 420. Since the valve 422 is closed the liquid refrigerant cannot flow in that direction but flows through tube 424 to the manifold 426 which is better shown in Fig, 4. From manifold 426 the liquid flows through the several tubes 428 to the right-hand group of evaporating units 3| which are connected in parallel between vthe manifold 428 and the manifold 430. After passing through the various evaporator units 3| the liquid flows through the manifold 430 (see Fig. 4) to the capillary restricting device 40|, which causes a reduction of pressure such that the refrigerant will evaporate in the left-hand group of evaporator units 3| after passing through the manifold 428 (see Fig. 4). The refrigerant chamber Within each of the evaporator units 3| ls shown as the conical, annular space 432 in Fig.-3. I

The vaporized refrigerant then passes through tubes 421 (see Fig. 4) to the manifold 425 and out through the tube 423 to the interior of the valve housing 4|9. It is at this point free to pass through the tube 4|1 and into the chamber 4|5 where it is stopped on one side by the diaphragm 435 and on the other side by the closed valve 4|3. Valve 42| in housing 4|9 is, however, open, allowing the refrigerant vapor to flow along the uted stem of the valve 42| into the chamber 431 and out the passage 438 to the suctionV tube 1|, thus completing the circuit. Y, Y rf During the portion of the cycle thus represented and described, the warm liquid refrigerant passing through the right-hand group of the evaporator units 3| will supply heat for melting the cones of ice 440 free from the conical surfaces 442 so they may oat upwardly in the water contained within the tank 444. At the same time the low pressure refrigerant in spaces 432 of the left-hand group of evaporator units 3| will be causing the freezing of similar cones of ice 44| on the surfaces 443. Before the conesof ice 440 have melted free from the surfaces 442 they have close thermal relation'therewith and the heat of the Warm liquid refrigerant passing through the right-hand spaces 432 is mainly utilized in melting the ice free from the surfaces 442. As soon as the ice 440 has detached itself from the surfaces 442 and floated upward in the water contained in the tank .444 the rate of heat transfer from the warm refrigerant in right-hand spaces 432 to the surfaces 442 will be materially reduced and therefore the outer Wall of the evaporator units 3| will rise in temperature and by conductivity will warm its upper extension 446 and thereby the bulb 448 which is socketed'tlerein in good thermal contact therewith. In this respect it is to be understood that the rate of transfer of heat between a metal wall and ice is greater than between the same wall and water of the same temperature as the ice. This causes the volatile liquid 450 contained in the bulb 448 to vaporize 8 until its vapor pressure balances with the increased temperature and this vapor pressure acting through the tube 482 causes the bellows 484 to expand moving the push rod 458 to the left and thereby moving the lever 481 which is pivoted upon the shaft 462. This movement is opposed by the toggle spring 483 and assisted by the valve spring 465 acting upon the left-hand vapor valve 42 This counter-clockwise movement of the lever ter. re-expands to produce a still further movement in a counter-clockwise direction and the' lower end of lever 451 engages the stem of vapor valve 422. The right-hand, vapor valve 422 is thus moved from its seat by the combined effect of spring 463 and the movement of diaphragm 436, which also causes diaphragm 435 to move to the left, striking the'stem of valve 4|3 and causing this valve to open. 'I'he connecting rod 486 having moved to its extreme left position, the arcuate portion 459 of lever 451 drops into the notch in the connecting rod 486 and holds the connecting rod 468 at its extreme leftward position. At the same time the valves 4|2 and 42| are closed by their respective springs while valves 4|3 and 422 are opened. The upper end of lever 451 is free to'move to its extreme leftward position because of the fact that the bellows 4,53 is contracted due to the low temperature existing within the bulb 441.

The pivot shaft 462 is secured to the casing 4 39 as shown in Fig. 6. Any suitable mechanical connection may be made between the lever 481 and the connecting rod 486, such for instance as a toggle linkage which would serve to hold the connecting rod 466 at either of its extreme movements as is done with the piston 24 in Fig. l. A bellows may be substituted for the diaphragm 436 and another bellows for the diaphragm 435. The expansive movement of such a bellows or diaphragm, having a much larger area than the valves 42| and 422 and being acted upon by the same liquid pressure, will supply ample energy for opening the valves against liquid pressure and their respective springs.

After the counter-clockwise movement of lever 451 as above described, the path of refrigerant from the tube 15 will be through the coil 405, the tube 409, past the open valvev 4|3, through the tube 4|1 and the tube 423 to the manifold`425 which distributes it to the left-hand evaporator units 3| for the purpose of melting free the rings of ice 44| while new rings or cones of ice are frozen to replace the recently released cones of ice 440, which are 4now floating in the water in 'tank 444. The heat supplied by the warm liquid semi-rigid manner as above theplate 41B. The

insulating material 416 supports the evaporator units 3| but is preferablv made ofmaterial having sufficient compressibility to allow these evaporator units to adapt themselves to fit the interior of the cones 442 and 443 which are integral with the removable tank 444. The bulbs 441 and 448 are supported by the split tubular inserts 411 which are seen in horizontal cross section in Fig.

5. since the tubes m and 452 are of small diarneter and quite exible, they may be readily straightened out so that the sheet 415 can be removed from the insulation 416, whereupon the bulbs 441 and 448 together with their respective split bushings 411 may be withdrawn from ythe balance of the assembly. By providing openings in the sheets 415 large enough to allow the passage of the bulbs 441 and 448 the entire evaporator aassembly may be separated from the valve assembly by removing these bulbs and by disconnesting suitable unions (not shown) in the tubes 423 and 424.

While the liquid valve 4I2 is open the supply of warm liquid refrigerant will be flowing through the coils 404 to increase the temperature of the bellows 454. This is for the purpose of preventing condensation of the volatile fluid 450 from the bulb 440 into the bellows 454. This heating of the bellows 454. although to a higher temperature than is even attained by the'bulb 448, will not cause the bellows to expand since the bulb 448 has ample volume to contain all of the fluid in liquid form.

It will be noted that the insulating material indicated by the broken line 403 surrounds all of the valves and passages which are called upon during any portion of the cycle to convey warm liquid refrigerant within the refrigerated space enclosed by the insulated wall 402. This is for the purpose of conserving the heat in the liquid refrigerant until it can be employed for the puri temperature and 10 consequently they may be em- 4llioyed for direct contact with the airin the en closed cabinet for cooling such air and thus real ize .the usual purpose of a. mechanically refrigerated cabinet without encouraging more than a minimum amount of condensation ofthe moisture in the air upon the tank walls.

Although a number of different modifications of the salient features of the present invention are disclosed in the accompanying drawings, it will be readily seen by those skilled in the art, upon the disclosure to them oithe teachings herein, how the'structures disclosed may be modified and/or changed without affecting the principles of the broad invention. Accordingly, it is to be understood that formal changes may be made in the specific embodiments of the invention disclosed without departing from the spirit and substance of the broad invention, the scope of which is commensurate with the appended claims.

What isjclaimed is:

L The method of refrigerating two thermallysegregated zones, controlling refrigerating eiects ln accordance with the individual requirements of said zones, and employing heat transferred 'from high pressure refrigerant owing toward crates in one of said elements and pose of melting the cones of ice free from the surfaces 442 and 443. Instead of providing a heat exchanger between the cold vapor line and the warm liquid line, I purposely hold the heat in the liquid and employ it to free the cones of ice from the surfaces upon which they have been frozen.

It will also be noted that in Fig. 3 in particular, all surfaces that are liable to be refrigerated to a temperature of less than 32 degrees F. are insulated, not only to prevent the loss of heat from such of them as may also contain warm liquid refrigerant, during certain portions of the' cycle,

but also to prevent the airin the cabinet in which the mechanism is housed from becoming dehydrated from contact with and causing frosting of a surface or surfaces below 32 F. in temperature.

This preferably applies to evaporating surfaces,

Athe evaporator elements 3|, as the remaining walls of the tank will never be below freezing one of said zones to aid in the control o1' the other zone.

2. Ina refrigerating system employing a volatilerefrigerant, a pair of heat exchange elements, means for directing the flow of said refrigerant so that atcne time the greater part of it evapat another time the greater part of'it evaporates in the other of said elements, a liquid refrigerant storage receptacle, and means in said system for placing said receptacle in communication with whichever one yof the two heat exchange elements is more active as an evaporator, said storage receptacle being adapted to store excess liquid refrigerant during the active evaporating period of one of said elements.

3. In a refrigerating system employing a vola- Y tile refrigerant, a. pair of heat exchange elements, means for directing the flow of said refrigerant so that at one time it evaporates in one of said elements and at another time it evaporates in the other of said elements while condensation of said refrigerant occurs in the one of said elements not being employed as an evaporator, a

liquid refrigerant storage receptacle, and means in said system for placing said receptacle in communication with whichever one of the two heat exchange elements is active as an` evaporator, said receptacle being adapted to store excess liquid refrigerant during the active evaporating period of one of said heat exchange elements.

4. The method of refrigerating two thermally segregated zones by circulating a v olatile refrigerant to evaporate in heat exchange with one or the other of said zones, controlling refrigerating effect in accordance with the requirements of at least-one of said zones, and transferring heat from high 'pressure refrigerant flowing toward one of said zones-to aid in proportioning the total cooling effect between said zones. v

5. In a refrigerating system employing a volatile refrigerant, a pair of heat exchange elements, means for directing the flow of refrigerant so that at one time the greater part of it evaporates in one ofsaid elements and at another time the greater part of it evaporates in the other of said elements, a liquid refrigerant storage receptacle adapted to store excess liquid refrigerant during Y 2,448,492 Y 1 1 o 12 the active evaporating period of one of said elements, means in said system for placing Said UNITED STATES PATENTS receptacle in liquid ow communication with the Number N one of thesaid two heat exchange elements which 1 523 112 mtzgf J D?? 925 is more active as an evaporator, and control l 1'735498 Etienne Nan' lz 29 by said elements- LEN, Y 2,005,360 Huntington ::IJune'zsf 1935 G NMUFF. IL m 2,049,413 cannon Aug. 4, 1936 2,145,774 Muffly Jan. 31, 1939 REFERENCES CITED The following references yare of record in the file of this patent:

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