US2190046A - Refrigerating method and apparatus - Google Patents

Description

Feb. 13, 1940. J. F. RoBlNsoN ET Al.

I REFRIGERATING METHOD AND APPARATUS sheets-sheet x Filed Aug. 1o.A 1937 vl. v

J. F. ROBINSON ET AL RFRIGERATING METHOD AND APPARATUS Filed Aug. 10, 1937 3 Sheets-Sheet 2 F25 /j 9 o Y 'Il A6 i Josep/7 E Robi/won Feb. 13, 1940.

Feb. 13, 1940. J. F. ROBINSON r-:T AL 2,190,045

i REFRIGERATING METHOD AND APPARATUS Filed Aug. 10, 1937 5 Sheets-Sheet 3 INVENTORS Josey/9 /1' /Pvb/hsom ATTORN EY Patented Feb. 13, 1940 UNITED STATES PATENT GFFICE,

San Francisco, Calif.

, assignors, by mesne assignments, to Cold Control Corporation, a corporation of California Application August 10,

9 Claims.

The present invention relates to methods and apparatus for refrigeration purposes, and especially to food storage and preservation through the use of prepared substances such as solidified gases which have temperatures very much lower than the freezing temperatures of water and water solutions.

Due to the compactness and lightl Weight of bloclrs of the so-called dry ices as compared with the great heat-absorptive capacities thereof, and their direct transition from solid to gas eous form during heat absorption they--especially CO2 which is odorless and non-poisonousare very desirable refrigerant's. However, due to the relatively high initial cost of Dry Ice and the inability heretofore of efficiently handling it under normal Arefrigerating conditions because of its extremely low temperature and rapid rate of heat absorption, its potential possibilities in the commercial field have been realized in only a small way. Another past objectlon to Dry Ice under existing methods of use is that it' causes foodstuffs to reach temperatures so low as to be either damaging or the cause of excessive hardness. Freezing, or overfreezing, may virtually destroy some food products and remove freshness and tastefulness from others, and in the case of certain products that are to be dispensed directly from a refrigerator tothe purchaser for immediate consumption it keeps them at an inedible consistency.

In general, dry ice refrigeration cabinets operate on a thermal recirculation principle, with cold air passing from the ice block to the food storage compartment and warm air passing from the latter to the ice block. Such methods, even when some control is exercised over the rate of air circulation, have proved lacking in eiliciency and are unsatisfactory because of the fact that Dry Ic absorbs heat so rapidly that the rate can not be effectively `controlled in a direct thermal system and also because the ice block can not be economically held in storage or conserved when the food storage compartment has reached a desirable low temperature. In short the Dry Ice is consumed too rapidly, with costly losses, and the temperature in the storage compartment becomes unnecessarily and, in fact, undesirably low.

Accordingly, it is the prima-ry object of the present invention to devise a method and an l apparatus lfor the use of Dry Ice in such manner that the rate of heat transfer can be effectively regulated to a satisfactory and economical de- 55 gree. 'I'his object contemplates not only an ac- 1937, Serial No. 158,419

(Cl. (i2-91.5)

curate regulation of the` refrigeration tempera- 4ture but also the prevention of waste of ice at any time and especially when the heat transfer is greatly retarded or substantially stopped.

'Ihe foregoing object is achieved, by a simple and inexpensive apparatus later to be described.

to the extent that desirable refrigeration tem-v peratures can be maintained and controlled within a three degree range for a continuous period or as long as the ice block lasts, and without regard to the varying size of the block during its consumption.

In effect, then, the present invention consists principally in successfully valving, automatically and accurately, the rate of heat transfer to an extremely cold refrigerant such as Dry Ice. The principles of the invention can be ap'k plied to uses other than that of preserving or solidifying foods-for example, it may be used to freezewater for skating rinks and maintain the frozen ice at proper temperature-but it is intended primarily to afford a sensitive regulating valve for controlling the flow of heat between two completely separated and insulated chambers.

It is a major object of this invention to devise a system of the character discussed in which an extremely rapid heat transfer can be effected between the refrigerant and the refrigerated device until the latter reaches a predetermined low temperature and yet in which theheat transfer can be substantially cut off without ineiiiciency. In the preferred arrangement, yet to be described, a single moving part is employed, the refrigerated device can be brought from 65 degrees F, to zero F. in less than one hour when using solid CO2, andthereafter the moving part is in operation only about five minutes out of each hour for the purpose of maintaining the zero temperature. During the other fifty-five minutes there is only a small slow leak between the refrigeration and Dry Ice compartments, andthe Dry Ice is effectively, as at all times, surrounded by CO2 gas and also otherwise insulated against ingress of heat from the atmosphere.

It is a further major object of the present invention to utilize frozen Water, or any equivalent medium as a valve for automatically regulating the rate of heat flow to an insulated, extremely cold refrigerant in response to variations in temperature of the valve itself.

Another important object consists in automatically varying the rate of heat flow to a refrigerant which is in contact with heat transfer means, ,by automatically varying the effective area of refrigerant presented to said heat transfer means.

Still another object of this invention is to provide a refrigeration system using Dry .Ice or the like as the initial or primary refrigerant, an endless belt of liquid of extremely low freezing point as the secondary refrigerant or heat transfer means, and means for causing and stopping the circulation of said liquid.

More in detail, it is an object of our invention to devisean efficient Dry Ice cabinet having an insulated ice block compartment, a separate insulated refrigeration compartment, a separate insulated pump and motor compartment and a iiuid circulation line connected to said pump and establishing a circuit of flow through the several compartments in series. In this connection it is also an object to control the motor automatically in response to temperatures within the refrigerating compartment.

From the foregoing it will readily be seen that it is a major object of the present invention to provide an eicient and relatively inexpensive refrigerator which is specially adapted to use Dry Ice and which has a minimum number of moving parts, practically free of mechanical up keep.

It is also an object to devise an improved cabinet structure having associated ice and food storage compartments.

These and further objects of the present invention will clearly appear from a study of the following detailed description when taken in conjunction with the accompanying drawings and4 the appended claims.

In the drawings:

Fig. 1 illustrates a plan view of a preferred form of cabinet structure and refrigeration system embodying the present invention, with compartment covers removed and with the water shell eliminated for clarity of illustration.

Fig. 2 represents a side elevational view of the apparatus seen in Fig. l, with only the ice compartment cover removed.

Fig. 3 is a view in end elevation of the appa# ratus of Figs. 1 and 2.

Fig. 4 shows, in enlarged fragmentary section, some of the details of the ice compartment as seen when looking upon the plane represented by line 4 4 in Fig. 3.

Fig. 5 is a slightly modified form of pump com partment with its accessories, shown in top plan.

Fig. 6 is a diagrammatic view looking forward in a refrigerator car, or truck, and illustrates the application of our refrigerating system thereto.

With continued reference to the drawings, wherein like characters are employed to designate like parts, the preferred embodiment consists of several major portions comprising a thoroughly insulated ice or refrigerant compartment I, a thoroughly insulated refrigeration or food storage compartment R, an insulated pump compartment P and a circulation system C for conveying a liquid medium through the several cornpartments in series. The system C may be said to include the pump, and also one or more automatic control devices.

In structural formation, which is quite important from the standpoint of long life, portv ability and efciency, the cabinet assembly comprises an internal structure covered by a top sheet metal plate or panel I', a bottom plate 2,

end plates 3 and side wall plates 4. Two no nmetallic frames of insulating material, such as wood, are provided to shape and support or reenforce the top and base of the cabinet respectively. The top frame comprises two outside longitudinal members 5; two end cross members 6, securely fastened to the members 5 by lap joints or any other suitable means; two further cross members 1, spaced apart and dovetailed into the side members 5, and interconnected by two short longitudinal members 8 which form therewith a rectangular framed opening of predetermined size; and two further cross members 9 bridging the members 5 and interconnected by three short longitudinal members l which cooperate in forming two further rectangular frames or openings of predetermined size. The three top openings, thus formed, provide access to the three compartments R., I, and P.

The lower cabinet frame comprises two longitudinal members Il and two cross members l2, properly secured together in rectangular formation; and two pairs of cross members i3 and lll, respectively, which are provided primarily for supporting `a pair of non-metallic platforms l5 and I6, respectively. The platform I5 supports an upwardly opening refrigeration box H, formed of sheet metal with all seams or edges sealed in any suitable manner. box are fitted and attached to the framed opening, previously described for the refrigeration compartment.

The other platform I6 may simply comprise the bottom of a second upwardly opening box I@ when the latter is formed of wood or other nonmetallic material, as illustrated. The platform would support a box complete in'itself if the box were of sheet metal like the box I1. This box ld when properly divided forms the ice compartment I and the pump compartment P. The di- `vision members comprise non-metallic panels i9 and 20 which form a sidewall and a bottom of the pump compartment. The latter may of course be completely formed as a small independent box for insertion within or adjacent the ice compartment, it being understood that the compartments preferably will be well insulated with respect to each other.

The several outside covers for the framework and box assembly may be anged where they meet, secured to the framework and finished at the corners or edges with angle strips, as shown; and they may be enameled externally or plated or otherwise coated in desirable colors. The top cover. i will of course be provided with apertures registering with the open tops of the three compartments (when, as in the illustrated embodiment the compartments open upwardly) and lpreferably this top cover has iianges turned downwardly at the edges of these openings (see for example, ange 2| in Fig. 4 and flanges 22 in Fig. 2).

The upper edges of the sidewalls of box I8 (see Fig. 4) may be secured to frame members 9 by screws 23, In like manner screws may be used to hold the upper edges of the other boxes, as well as the flanges of the top cover I, against those frame members to which they are in proxirnity. A cross beam 24 is attached to members 8 in such position that it divides the upper part of the chamber R in half.

All of the wooden parts preferably are given a coating of shellac or the like to prevent moisture absorption.

Adequately insulated covers (see Fig. 2) are provided for opening and snugly closing the upper ends of the compartments. The Ipump compartment has a cover 3l, preferably without a handle. Handled covers 32 close the chamber R and a similar cover will be placed over the ice chamber. heat insulator such as fibrous Kapok, is provided to be packed snugly atop the Dry Ice block, shown at 26 in Fig. 4. Also, heavy sheets 56 of good insulating material are used to line the sidewalls of the ice compartment. All of the space around the several compartments, as well as the spaces between the compartments, are lled or packed with Kapok, which preferably is precut and formed into pads or 4blankets 28, 29, 30, etc. of proper sizes to t the several spaces. The spaces may be better sealed and placed under partial vacuum to provide insulation, and an automatic vacuum pump mechanism added to maintain said vacuum. We have found that insulation eiiiciency can be further increased, and undesirable moisture kept out of the insulating spaces of the cabinet, by lining the covers I, 2, 3, 4 interiorly with sheets of specially prepared laminated paper comprising cellulose material and petroleum base material arranged in alternate layers.

Before the insulation is put in place and the sides or covers thereafter assembled it will be understood that the cold control apparatus must be installed and all pipes and electrical conduits laid. Briefly, the cold control mechanism or system C affords an automatic valve or transfer Y device for establishing just the requisite heat transfer, between the otherwise fully insulated compartments, to maintain the compartment R at a predetermined lowy temperature, usually in the neighborhood of or somewhat above zero, Fahrenheit, but lower if desired. This apparatus comprises the following parts.

As seen in Figs. 1 to 3, the side walls of the box Il of the compartment R have a small tube 33 laid thereagainst in a series of loops 34 and held in position by straps 35. One end of this tube passes through the box Il adjacent the ice compartment and is bent to extend upwardly through the bottom 20 of the pump compartment,

where it is connected to the side of a vertical-A 'Ihis reservoir has a large liquid reservoir 36. ller plug 3l at its top and an outlet tube 38 connected at its bottom, said tube being bent to make connection with the suction side of a small rotary pump 39, mounted within the same compartment P. The pump is driven by a small electric motor 40, constructed as a unit with the pump to form in effect a single rotary element. 'I'he motor carries a small fan 4I on its shaft for the purpose of circulating air within the compartment to maintain uniform temperatures therein.

A relay control box 42, located within the pump compartment, is fed by electrically insulated wires 43 which are carried outwardly through a conduit 44 for connection through a plug or socket 45 with an external pair of conductors 46 designed for convenient connection with an available source of electricity at suitable voltage. This source may be the line of a building, or the battery of a truck or boat. In fact, so little power is required to operate the pump and the latter is in operation for so small a part of the time that dry cell motors actuated by dry cells may be used as self-contained units.

The relay, conventional in form, has a switch automatically operated by a unit 41 in response to variations in temperature within the compartment R. This is accomplished by connecting the In addition a pillow 25 filled with a goodunit 4l through a tube 48 with a thermostat 49 that is disposed within the compartment R, and illling the members 41, 48 and 49 with a liquid of very low freezing point. Expansion and ccntraction of course causes the switch actuation and it will be appreciated that any conventional mechanism of any suitable type will suilice for this purpose when accurately adjusted for sensitive regulation. The relay and motor are interconnected by wires 50 so that the latter automatically starts and stops when the switch is closed or opened.

The block of ice does not rest directly upon the compartment bottom I6, but sets upon a radiator assembly or heat transfer device 5| which is supported by said bottom and fitted beneath the lower edges of the insulating sheets 56. The radiator assembly includes a plurality of horizontal pipe loops 52 in series, connected at one end to the discharge side of the pump by a pipe 53 and at the other end to the intake end of the tubing 33, the latter having been bent and passed from the compartment R toward the radiator for this purpose. If desired, the loops 52 and pipe 53 may constitute a continuation of the pipe 33 but preferably, for convenience of manufacture and assembly, the radiator is made as a separate unit even when all pipes are of the same size. The wall thickness and diameter of the tubing within the compartment R may vary and be relatively large but it is essential, to maximum eiciency and sensitivity of control, that the pipe sections which ypass` from the radiator to the compartment R be rather small and thin. 'I'he reason for this is that, once the refrigeration compartment reaches the desired temperature and the pump stops circulating liquid through the system C, only a very small and slow heat leak is permissible from the relatively warm compartment R to the extremely cold compartment I. The maximum leak or heat ow by conduction via direct connections is determined by the size of the interconnecting tubing, which constitutes the only direct connection. It is likewise desirable that the connection from the radiator to the pump be of minimum size.

The radiator assembly may but not necessarily include a plurality of fins 54 for quickening the heat transfer between the loops 52 and the ice block; and preferably the assembly further ing horizontal but is designed to bulge upwardly when' the water freezes.

The secondary refrigerant or circulating medium, within the series of pipes, preferably is Zerone-a commercial liquid which will not freeze at the temperature of Dry Ice. Any other liuuid having similar characteristics will suffice. A vent 5T is provided adjacent the top of the compartment I to relieve pressure by discharging the CO2 gas. This gas preferably is passed into the spaces occupied by the Kapok insulation and increases the insulation eflciency thereof.

The pipe 53 is bent upwardly, as best seen in Fig. 2, where it leaves the discharge side of the pump, so that the pumping element will always be immersed in liquid and never requires priming. The low point of pump connection to the reserllo ' to the floor 62.

voir ensures a liquid supply to the pump as long as the reservoir contains any liquid.

The pump compartment and its accessories are modified in the form shown in Fig. 5, only to sufiicient extent to permit ready removal and replacement of the pump and motor unit, the pipe 38 and the reservoir 36 as a unit structure. This facilitates servicing in event of trouble. The alteration is chiefly a matter of arrangement of parts, the only added elements consisting of a pair of detachable pipe couplings 60, one where the pipe 33 approaches the reservoir and the other in the pipe 53 where the latter is bent upwardly in its approach to the pump. The pipe 53 passes downwardly through the center of the compartment instead of vertically through a corner as in Fig. l, the reservoir, thermostat switch and pump being set adjacent one side to permit this variation. The thermostat pipe line 48 is elongated and bent to conform to the interior shape of the compartment so as not to interfere with vertical removal of the multi-part unit 36, 38, 40. Likewise the electrical supply wires 44 are laid in an out of the Way position.

The invention is well adapted for use in refrigerator trucks and railroad cars wherein the dry ice may be disposed in a cabinet or compartment suitably insulated from the insulated walls of the vehicle. In the form of invention illustrated in Fig. 6, reference numeral 6| indicates, generally, a refrigerator railroad car, truck, or any other refrigerated storage space having a floor 62, side walls 63, a top wall 64 and an end wall 65, all of which are thoroughly insulated and constitute a rerfrigeration or food storage compartment. Disposed within the compartment 6I and preferably against one end wall thereof, is the dry ice or refrigerant cabinet or compartment 66 secured by any suitable means, as brackets 61, Arranged lengthwise of the space 6I and secured to the top wall 64 thereof by any suitable means is a radiator assembly or heat transfer device arranged in two sections generally indicated at 68 and 69 or in slome instance we may find it desirable to provide only one section, ex-

ktending substantially throughout the length of the space. Each section consists of one continuous tube or pipe 10 turned back on itself at each end of the section to form a series of elongated paralel loops embraced by a multiplicity of radiating ns 1l. The tube 10 may be continuous through both portions of each section or one side of each end of each section may be interconnected by a removable section of pipe or tubing. 'I'he opposite sides of each end of each section are connected by suitable f tubing 12 and 13 with pumps 14 and 15 and with a reservoir and automatic switching mechanism disposed within the dry ice compartment 66 in like manner to the arrangement illustrated in Figs. 1 to 3. Both pumps 14 and 15 are embraced within electrical circuits and are controlled by independent and manually actuated switches 1'6 and 11 for starting and stopping operation of the system. When the system is started subsequent and intermittent starting and stopping of the pumps is automatically caused by therelay control switch working in conjunction with a thermostat 18 disposed within the space or refrigeration compartment, in like manner to the thermostat 49 illustrated in Figs 1 and 2.

As illustrated in Fig. 6 two sets of radiators or heat transfer devices 68 and 69 are employed. One set 68, adapted for operation independent of the other, is connected as aforesaid by pipes 12 with the pump 14 and by pipe 13 with the other heat transfer device disposed within the cabinet 66 so that operation of pump 14 alone will cause circulation of the Zerone through the radiator 68 and the radiator within the cabinet 66. When pump is also running, circulation of Zerone will take place through the radiator 69 and the radiator within the cabinet 66 by means of the pipes 13 and pipe 16 interconnecting the two portions of said section. By the foregoing arrangement both sections may operate simultaneously or independent of each other. By thus dividing the radiators into sections we are enabled to closely control the refrigeration temperature under varying conditions and to selectively refrigerate all of a compartment or portions thereof according to requirements.

Operation In preparing the cabinet for operation the screw top 31 is removed from the reservoir 36, and Zerone is poured slowly in to displace air from the tubing. Connection is then made to a source of electricity, causing the motor to drive the pump, which draws fluid from the reservoir and forces it through the series of pipes and loops driving all air ahead ofit into the reservoir for escape to the atmosphere. A few pints of liquid will fill a normal size system, and when the level reaches a point about one inch below the reservoir top, the cap is replaced tightly. It is assumed that a block of Dry Ice has been placed in the compartment I, that food has been stored in the compartment R and that the hand covers have been fitted in place to close the several compartments.

The thermostat continues to call upon the motor-pump device for circulation until the loops 34 have absorbed sufficient heat from the refrigeration compartment to bring it to predetermined low temperature. Circulation of Zerone will take place at a rate governed by viscosity, pipe size, number of loops, motor size and pump capacity, etc., all of which must be carefully predetermined to obtain maximum results.

Very shortly after insertion of the ice block and prior to the time that the motor switch is automatically opened to stop the circulation, the water in the radiator 5I has become frozen and in so doing its expansion has caused the top of the shell to become convex. The Dry Ice block is then no longer in full surface contact with the shell, so that an automatic valving of the heat flow has taken place. 'Ihe frozen water is now in the form of an ice jacket enclosing the radiator tubes and ns, and it continues to automaticallvalve or check the heat thransfer, as follows.

Water, above freezing point, is an excellent heat conductor. siderably decreased, and as it becomes colder and colder in solid form it becomes more and more an insulator. Also, the thicker the ice the greater becomes its resistance rto heat transfer. Hence the frozen water in 'the shell automatically checks the ow of heat from compartment R to compartment I, and this is very important when an extremely large temperature differential exists between the primary refrigerant (Dry Ice at 109 degrees below zero, F.) and the refrigerated compartment (air and contents at 20 deg. F., e. g.). This automatic effect is not relatively great when the Zerone is circulating but it becomes very `appreciable when circulation ceases, for then heat can leak only along a short section of small When frozen its conductivity is con-4 pipe by direct conduction to the radiator loops perature to become a good insulator.

and thence to the Dry Ice block via the water ice jacket. This leak can be further decreased by coating the tubing with self-vulcanizing rubber or the like where it leaves the radiator and passes through the wall.

As the circulating liquid picks up heat from the compartment R it first passes through the pump compartment warming the operating units thereof, and then it is discharged by the pump to the radiator loops within the ice jacket to cause the latter to become warmer and a better conductor of heat. Heat is very rapidly extracted from the ice jacket by the Dry Ice block. The liquid becomes cooler and cooler as it recirculates, and ultimately the thermostat cuts open the motor switch to stop the pump, whereupon circulation ceases and the ice jacket reaches a very low tem- The Dry Ice block is very effectively preserved during the lull or standby, and this results in large economy as the periodical standby periods are many times greater in length than the intermittent periods of liquid circulation.

Even without the shell 55 and its enclosed ice jacket, the emciency is remarkable in comparison with past systems of Dry Ice refrigeration, for as previously explained the automatic control of circulation through a pipe of limited area adjacent the ice box radiator outlet is in itself an effective valve or check upon the transfer of heat in a system having a high differential of temperatures.

In reducing our invention to practice we have constructed acabinet having 7 cubic feet of space in the refrigeration compartment and tubing of inch diameter, with 24 feet of such tubing arranged in loops within said refrigeration compartment. In such an arrangement, with the space carrying a normal load of foodstuffs and with commercial Dry Ice as the primary refrigerant, we have brought the refrigeration space from 65 deg. F. to zero F. in about one hour, and have thereafter maintained the zerortemperature within a 3 degree limit with the pump 0perating only five minutes out of each hour over long periods of time, and with very low Dry Ice consumption, particularly during the period following the initial cooling of the refrigeration compartment. The outside dimensions of this cabinet assembly, constructed as illustrated in the drawings, were approximately 31x31x52 inches.

'I'he water ice block in addition to its other functions serves as a reserve or safety unit. Should the operator or attendant inadvertently let the Dry Ice supply become exhausted, the water ice block will absorb heat over a considerable time period and prevent loss of or damage to the contents of the refrigeration compartment.

The thermostat preferably is adjustable, in a manner not shown, to vary the temperature to which it responds.

It should now be apparent from the foregoing description that -the stated objects are accomplished by the present invention, and that we are able to commercially use refrigerants such as dry ice which are relatively expensive, in an economical manner. It will be understood that the disclosure here made is illustrative and not restrictive, and that many alterations and modifications involving the substitution of equivalent parts may be made. For example, it is contemplated that an ice skating rink may take the place of the refrigeration compartment, and as illustrated in Fig. 6, the insulated interior of a refrigerator car or truck may constitute a refrigeration compartment within which is disposed, and insulated therefrom, the Dry Ice storage compartment. 'Ihis same general arrangement may be carried out in other installations and adaptations of the invention, for example, in boats, large meat-storage compartments and in any other structure or space to be refrigerated. We wish, therefore, to have our protection limited only within a reasonably liberal interpretation of the appended claims.

What is claimed is:

l. In a refrigeration apparatus of the character described, a compartment 'designed to receive a solid and extremely cold refrigerant such as Dry Ice, means for transmitting heat to said compartment, said means including a receptacle containing liquid and having a surface arranged for contact with the block of refrigerant, the liquid having a freezing'temperature above the temperature of the refrigerant and said receptacle designed tc vary the shape of said contact surface in response to solidication of the liquid contained therein.

2. A refrigeration cabinet comprising a refrigerant compartment, a refrigerating compartment and a pump compartment compactly arranged and insulated, an endless liquid-circulation conduit passing through said compartments in series, said compartments otherwise being sealed relative to one another, a pump in the conduit at a point within the pump' compartment, an electric motor mounted as a unit with said pump and having a switch for cutting it into and out of operation, and means responsive to refrigerating compartment temperatures to actuate said switch.

3. In the cabinet construction defined in claim 2, said motor carrying a fan for circulating air in the pump compartment.

4. In the cabinet construction of claim 2, said conduit including a filler reservoir within the pump compartment at a level above said pump.

5. In a refrigeration apparatus of the character described, a compartment designed to receive an extremely cold primary refrigerant, a compartment to be cooled arranged adjacent said refrigerant compartment, a receptacle in the bottom of said refrigerant compartment for contact with the primary refrigerant, saidreceptacle containing a sealed body of liquid of a freezing point above the temperature of said refrigerant, a conduit containing a, secondary refrigerant and extending from said cooled compartment into the liquid sealed within said receptacle.

6. In the combination defined in claim 5, the portion of said conduit within said receptacle being designed for rapid heat conduction and to permit the upper side of said receptacle to assume a flat horizontal position.

7. Ina refrigeration system of the character described, a compartment designed to receive a solid and extremely cold refrigerant such as dry ice, a refrigeration compartment, a heat transfer line between said compartments, means for intermittently circulating a secondary refrigerant through said transfer line, and a closed receptacle filled with a normally frozen liquid and containing that part of said transfer line which transmits heat to the refrigerant compartment, said receptacle arranged for direct contact with the solid refrigerant.

8. In the combination defined in claim '7, said compartments being separated and insulated rel s ative to each other, and said transfer line being has a freezing point much higher than that of the dry ice, said flexible wall of said receptacle designed to vary its area of contact with the dry ice automatically in response to temperature changes within the receptacle, and means for transferring heat from said means to be cooled to said compartment substantially solely by way of said normally frozen liquid.

VAN HOUDEN KING, JR. JOSEPH F. ROBINSON.

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