US2262635A - Refrigeration - Google Patents

Description

Nov@ 11, 1941. c. c. cooNs 2,262,635

REFRIGERATION Filed Nov. 25, 1938 2 Sheets-Sheet 1 I I I I I I I I l I I I I I I I l I I I I I l I I I I I I I I I I I I l I l l I I lllllllllll l l l l I lll l I I l I IlllllIlI I n l I u I l I I I v l l l l I n l l l l I x I l l x 1 C J l l I I I l 58 ||||||l|||| l I l I r ||||l|||| ll'l/lllllllll//llllll l/lll/l/l/llll/ l/l/ .l INVVENTOR Carli@ C. Cooks ATTORNEY Nov. 11, 1941. cfc. cooNs REFRIGERATION Filed N'ov. 25, 41938 2' sheets-sheet 2 w MMH .mh

INVE-NTOR Curtis C. Co'ns ATTORNEY Patented Nov. 11, 1941 REFRIGERATION Curtis C. Coons, North Canton, Ohio,

The Hoover Company, North Canton,

corporation of Ohio assigner to Ohio, a

Application November 25, 1938, Serial No. 242,221 17 Claims. (Cl. 6.2-5)

, vide a refrigerating system having a plurality of evaporator sections which are arranged to be individually supplied withliquid refrigerant from a common condenser in alternate periods and in which the control of the flow of liquid refrigerant from the condenser into the various sections of the evaporator is regulated by the production of ice in the evaporator and by the diversion of Waste products of combustion from a boile\ heater.

It is a further object of the invention to provide a refrigerating system of the type above referred to in which one section of the evaporator is arranged to favor production of refrigeration in a low temperature storage compartment 'and another section of ther evaporator is arranged to favor refrigeration in an ice-freezing section thereof.

It is a further object of the invention to provide a refrigerating system having a plurality of evaporators connected in a single inert gas circuit and provided with individual refrigerant supplies which are so constructed and arranged that there is no lpossibility of liquid refrigerant discharged into one section of the evaporator finding its way into another section thereof.

It is a further object of the invention to provide a refrigerating system including an evaporator so constructed and arranged that it is provided with rear box-cooling sections, forwardly projecting ice making and low temperature storage compartment refrigerating elements.

Other objects and advantages of the invention will become apparent as the description proceeds when taken in connection with the accompanying drawings, inwhich: k

Figure l is a diagrammatic representation of a refrigerating system embodying my invention in which the evaporator and associated control elements are shown on an enlarged scale and in perspective.

Figure 2 is a diagrammatic partial ,sectional view on an enlarged scale of certain control mechanisms.

Referring now to the drawings in detail and rst to Figure 1 thereof, the refrigerating system. comprises a boiler B, an analyzer D, a tubular air-cooled condenser C, an evaporator E, a gas heat exchanger G, a tubular inclined aircooled absorber A, a liquid heat exchanger L, and a circulating fan F which is driven by an electrical motor M. These elements are suitably connected by Various conduits to form a com- -plete refrigerating system including a plurality of gas and liquid circuits to which reference will be made in more detail hereinafter.

The refrigerating system above described will be charged with a suitable refrigerant, such as ammonia, a suitable absorbent, such as water, and an inert pressure equalizing medium, preferably a dense inert gas, like nitrogen.

The boiler B is arranged to be heated by a suitable combustible fuel burner H. The fuel burner H and the electrical motor M will be controlled in any suitable or desired manner by a control mechanism which is preferably responsive to temperature conditions Within the storage compartment of the refrigerator. A preferred con- 'trol mechanism is illustrated and described in my co-pending application, Serial No. 148,424, filed June 16, 1931, now Patent No. 2,228,343, issued January 14, 1941.

The application of heat to the boiler B generates refrigerant vapor from the solution therein contained. The vapor so generated passes upwardly through the analyzer D in counterflow relationship to strong solution flowing downwardly therethrough. In the analyzer further refrigerant vapor is generated from the strong solution by the heat of condensation of absorption solution vapor formed in the boiler. The refrigerant vapor is conveyed from the analyzer to the upper portion of the condenser by the conduit Il which includes the air-cooled rectier R. l

The weak solution formed in the boiler is conveyed therefrom through the conduit I3, the outer path of the liquid heat exchanger L and the finned solution cooling conduit I4 into the lean solution reservoir I6. The lean solution in the reservoir I6 is conveyed from the bottom portion thereof into the upper portion of the absorber A by a gas lift conduit I1. It is apparent that the upper portion of the absorber A is at an elevation appreciably above the liquid level normally prevailing in the boiler-analyzer system Wherefore some means must be provided to eleyate the liquid refrigerant thereinto.

purpose a small bleed conduit I8 is connected between the discharge conduit I9 of the circulating fan F and the gas lift pump conduit below the liquid level normally prevailing therein, whereby the lean solution is elevated into the absorber by gas lift action. The reservoir I6 is vented to the upper portion of the absorber by a small conduit 20.

The lean solution flows downwardly through the absorber in counterow relationship to a rich mixture of pressure equalizing medium and refrigerant vapor flowing upwardly therethrough. 'Ihe refrigerant vapor content of the mixture is absorbed by the solution and the heat of absorption is rejected to cooling air flowing over the 'outer surfaces of the absorber conduit and the air-cooling ns mounted thereon. The strong solution formed in the absorber is` drained from the bottom portion thereof into 'the upper portion of the analyzer D by means of the conduits 2|, the inner path of the liquid heat exchanger L and the conduit 22. l

'Ihe lean inert gas mixture formed in the ab sorber is conveyed from the upper portion therevof into the suction eye of the circulating fan F by the conduit 24. The inert gas is placed under pressure by the circulating fan and is discharged through the conduit I9 which opens into the inner path of the gas heat exchanger G from which the inert gas is conveyed bythe conduit into the evaporator E. The exact construction and operation of the evaporator will be described more fully hereinafter. For the present it is sufcient to note that the inert gas circulates therethrough and is discharged through the conduit 26 into the outer path of the gas heat exchanger G from which it is conveyed by means of the conduit 21 into the bottom portion of the absorber A through which i1; flows counter to the absorption solution in the manner heretofore described.

The evaporator E comprises a pair of vertically spaced horizontally extending large diameter box-cooling conduits 30 and 3l which are produit 31 joins the inert gas supply conduit 25( The left-hand end of the box-cooling conduit 3| joins the inert gas discharge conduit 26.

The ice-freezing ` evaporator conduits 32 and 33 are provided with a plurality of inclined spaced apart freezing plates 48 which are adapted to recelvethe inclined bottom portion of a water tank 42. The bottom portion of the water tank rests upon an insulatedv fast-freezing compart- `ment 38 which embraces the fast- freezing conduits 36 and 31 in its top portion. The fastfreezing conduits 36 and 31 are separated from the storage space within the insulated compartiarent 38 by means of a horizontal top wall plate The conduit 36 a For this completely enclosed in insulating material which preferably would extend upwardly from and 1ntegral with the insulation of the fast-freezing compartment 38. Of course the top portion of the tank 42 will not be insulated but it may be provided with an insulated removable cover.

The refrigerant vapor which is liquiiied in the condenser discharges therefrom through a conduit 44 into the top portion of a diversion cham-- ber 45. The bottom portion of the diversion chamber 45 is divided into two sections by an upstanding partition wall'46. A drain conduit 41 including a downwardly extending U-shaped liquid sealing portion connects the right hand side of the partition 46 with the ice-freezing evaporator conduit 32. A drain conduit 48 which also includes a downwardly extending U-shaped liquid sealing portion communicates the lefthand side of the partition 46 with thegas inlet portion of the fast-freezing conduit 31. The diversion chamber and the conduits 41 and 48 are vented to the inert gas conduit 25 by` a small conduit 49.

The right-hand side of the box-cooling con; duits 30 and 3| are connected by a small diameter drain conduit 50 which includes a U-shaped liquid sealing portion. The inert gas outlet end of the box-cooling conduit 3l is provided with a drain conduit 5I which communicates with the strong solution return lines 2| below the liquid level normally prevailing therein.

The boiler B is provided with a Waste products of combustion iiue which terminates in a diversion box 56 at a level slightly below the level of the evaporator structure. The diversion box 56 is provided with a vertically extending discharge ilue 51 and a laterally extending discharge ilue 58. A flap valve 59 is pivotally mounted within the chamber 56 in such position that it may be swung to prevent ow of waste products of combustion through either of the discharge conduits 51 and 58.

The nap .valve 59 is actuated `by means of a crank 60 which is pivotally connected to the actuating element of an overcenter snap action mechanismv 64 housed within a control box 65. A pair of pressure responsive bellows 61 and 68 are mounted in the left and right-hand sides, respectively, of the casing ,65, as viewed in Figure 2. The bellows 61 is connected by means of a capillary conduit 10 to a bulb element 1I which lispositioned within the tank 42 in position to be frozen into an ice block forming on the interior the ice-freezing evaporator conduit 32.

'Though the shallow tank 42 has been shoW-n' as being exposed so that it maybe contacted by air within the refrigerator cabinet, it may be wall of that tank over one of vthe plates 40 on the ice-freezing evaporator conduit 33. The bellows 68 is connected with a capillary conduit 12 which terminates in a bulb element 13 which is posi tioned within the tank 42 in position to be frozen into an ice block forming on the interior wall thereof in contact with one of the plates 40 on 'I'he bellows 61 and 68 are positioned to actuate the overcenter mechanism 64, thereby to actuate the flap valve 59.

The products of combustion discharge ue 58 extends upwardly as illustrated and receives a thermostat housing 15 which projects laterally from the diversion chamber 45 and extends about half way through the conduit 58. A s'piral bi-metallic thermostat 16 is mounted Within the chamber 15 and is connected to actuate the shaft 11 lof 'a diversion'plate 18 mounted within the diversion chamber-45. The diversion plate 18 is mounted in such relation to the condensate discharge conduit 44 and the dividing azeaess wall 46 that liquid discharging through the conduit 44 may be directed wholly to one side or the other of the plate 46 whereby the same is wholly diverted into conduit 41 or 48.

The above described mechanism will be enclosed in a suitable cabinet preferably with the refrigeratng mechanism suitably distributed in a lower mechanism compartment and a rear ver tically extending air-cooling ue with the exception, of course, of the evaporator which will preferably be positioned in the top ycentral portion of the food storage compartment.

The evaporator will preferably project forwardly in the apparatus whereby the front opening, which will be closed by a suitable insulated door, of the compartment 38 is readily accessible from the front portion of the box and the water tank 42 may be rendered accessible by a. small pivoted panel in the top portion of the refrigerator cabinet. This` construction will place the box-cooling evaporator conduits and 3| in the rear of the storage compartment adjacent the rear wall thereof.

The operation of the invention is as follows:

Assuming that the apparatus has not been operated and that the refrigerator ls warm, the normal control mechanism will energize the heater H and the circulator motor M to place the refrigeratng system in operation. There being no ice in the water tank, the expansible thermostatic elements 61 and 6,8 will both be moved to their expanded position but the snapaction mechanism will be in one or the other of its two possible positions.

Assuming that the apparatus is'warm and that the flap valve 59 is in the position shown in Figure 2, the products of combustion from the boiler heater will discharge through the conduit 51 and no heat will be applied to the thermostatic element 16 because there will be no waste products of combustion flowing. through the conduit 58.'v Under these conditions, the

freezing evaporator conduit 31. This liquid refrigerant will be projected through the conduits 31, and r33 by the rapidly flowing inert gas stream and will produce refrigeration in those thermostat 16 will have actuated the diversion w plate 18 to the position illustrated to discharge the liquid refrigerant flowing from the conduit 44 into the conduit 41. This liquid refrigerant will flow into the evaporator conduit 32 Ithrough whichit will be propelled by the inert gas stream through the conduits 32, 34 and 36. -Any refrigerant unevaporated in these conduits will flow into the conduit 3| where it will be evaporated to produce refrigeration for purposes of box-cooling at a relatively high temperature.

This operation of the apparatus will continue until ice blocks of a predetermined size have been formed within the tank 42 on those Wall portions thereof which are inv heat exchange relationship with the plates on conduit 32. When the ice blocks have reached the abovementioned predetermined size, the bulb element 13 will freeze therein which will cause the ther:- mostatic element 68 to collapse, whereupon the over-center mechanism 64 will be actuated by the expanded thermostatic bulb element 61 to operate the flap valve 59 in a clockwise direction to shut off communication between lthe conduit 51 and the chamber 56 and to permit products of combustion flowing through the discharge flue 55 to exit through the conduit 58.

The products of combustion owing through the conduit 58 will heat the thermostat 16 which will then actuate the diversion plate 18 in a clockwise 4direction whereupon all refrigerant liquid thereafter discharged will flow into the conduits. Any refrigerant liquid whichis not evaporated in the conduits 31, 35 and 33 will flow into the box-cooling conduit 30 in which it will evaporate into the inert gas stream to produce refrigeration for box-cooling purposes.

This operation of the apparatus will continue until ice blocks of apredetermined size have been formed on those portions of the inner wall of the tank 42 which are in heat exchange relationship with the plates 40 on the conduit 33. When the ice blocks reach the above mentioned predetermined size, one of them will freeze around the bulb 1| which will cause the thermostatic element 61 to collapse. 'If now the ice blocks previously formed on the side of the tank 42 which is refrigerated by the evaporator conduit 32 have melted free thereof, the bulb 68 will have expanded and will immediately actuate the snap-acting mechanism to the position illustrated in Figure 2 when the thermostat 61 collapses. This will again cut off communication between the conduits and 58, the thermostat 16 will cool, and the plate 18 will be actuated back to the position illustrated to again discharge liquid refrigerant into the conduit 41.

Therefore, .refrigeration is alternately produced in the right and left-hand sidesof the vevaporator and in the upper and lower box-cooling evaporator conduits.

The evaporator vconduits 32, 34, 36, 31, 35 and 33 are of relatively small diameter with respect to the quantity of gas discharged therethrough whereby the gas flows through these conduits at a velocity sufficiently high to sweep or drag the liquid refrigerant therethrough as it is evap- 'Iorating into the inert gas stream. Apparatus and methods by which the liquid refrigerant is propelled through an evaporator by the frictional dragging action of the inert gas flowing through the evaporator are disclosed and claimed in the co-pending application of Curtis C. Coons and William H. Kitto, Serial No. 386,395, filed April 2, 1941.

The evaporator conduits 3| and 30 will be inclined slightly to permit the liquid refrigerant to flow therethrough by gravity as the inert gas flows through these large diameter conduits too slowly to exert any propelling action on the liquid refrigerant.

With the evaporatorarrangement herein disclosed, the right hand side of the forwardly projecting portions of the .evaporator first produce refrigeration" in contact with the water tank thereby favoring the production of ice, whereas those Vportions of the evaporator projecting forwardly on the left-hand side of the apparatus first produce refrigerationvin the conduit 31 -which is in heat vexchange relationship 'with the low temperaturefast-freezing compartment 38.

thereby favoring refrigeration f or that purpose.

Each of the individually operated evaporator sections produces refrigeration for box-cooling purposes in approximately the same quantity and conduit y48 and will be discharged into the. fast- 75 for the same period of time. However, it should be noted that the refrigeration demands of the compartment V38 are relatively small because,

first, this compartment is of small sze, secondly, it is heavily insulated, andthirdly, it is not ordinarily called upon to carry any very large refrigeratng load though it is perfectly capable ally,

of assuming a heavy load, as for dessert freezing number by the simple process of ladling the blocks from the water in the tank 42.

'I'he control of thisp'articular apparatus automatically tends to gear they production of ice to seasonal demands. This is achieved as follows: During periods of warm weather the heat leakage into the storage compartment of the refrigerator will increase whereupon .the normal control mechanism will cycle'4 the apparatus more frequently which will result in a more frequent production of ice cubes. On the other hand, in periods of cool weather the heat losses through ,the refrigerator cabinet will not be so great, the

apparatus will cycle less frequently, and a lesser number of ice blocks will be produced. Therefore, the apparatus automatically produces a greater quantity of ice during periods of warm Weather when ice is in greater demand by domestic users. I

The control mechanism is so constructed and arranged that neither of the bellows 61 and 68 is able to actuate the over-center mechanism 64 from one position to the other if the opposing bellows is also expanded; that is,-it requires that one of the bellows 61 and 68 collapse before the over-center mechanism is enabled to change the position of the nap valve 59. This, therefore, insures that ice blocks of a predetermined size will be formed in the operative portion of theice freezing evaporator without interference even though ice blocks on the inoperative side of the ice freezing evaporator have melted free from they bottom walls thereof and the associated bellows has expanded.

Though specic 'constructions have been described in detail herein, obviously the invention is not limited thereto. For example, other forms and arrangements of` thermostatic mechanisms might be utilized with vequal effectiveness, and the evaporator conduits might be arranged in a different fashion. For example, the position of the water tank 42 and of the insulated fast-freezing compartment 38 could be reversed, if desired, therebyjoining the insulated top wall of the compartment 38' with the insulated top wall of the' refrigerator cabinet. Additionally, the thermolstatic'element governing the operation of the diversion plate 1 8 could be operated by alternately permitting Warm air owing from the heat rejecting condenser and/or absorber to 'contact -the same, thereby achieving essentially the same control as that specifically described herein.

The present invention provides a highly convenient and eicient'apparatus whereby ice may be produced continuously and stored in a refrigerated atmosphere until needed. Additionthe apparatus provides a. construction whereby ice is alternately produced in different refrigerating zones and the control is achieved in response, first, to demands for production of 'ice with gas which has already passed through the vprimary .evaporating zones in the fast-freezing and ice production evaporator sections, whereby the refrigerant must evaporate at higher temperatures in the box-cooling conduit,

While the invention has been illustrated and considerable detail, it is not described herein s to be considered as being limited thereto as various changes may be made in the constriiction,l proportion and arrangement of parts without departing from the spirit of the invention or the scope of the -appended claims.

I claim: y

1. Refrigerating apparatus comprising an evaporator including a pair of finned space cooling elements, a pair of freezing elements, means connecting said elements in series, means for propelling an inert gas through said elements,

liquid refrigerant supply means, and means for selectively directing liquid refrigerant into a selected portion of said evaporator in order to renl der only one of said box-cooling elements and one of said ice-freezing elements operative.

2. Absorption refrigerating apparatus comprising a solution circuit including a boiler and an absorber, an inert gas circuit including said absorber and an'evaporator, means for heating said boiler, means for supplying refrigerant vapor generated in said boiler to said evaporator in liquid phase, said evaporator comprising a pluin the different zones, and secondly, by controlling the path of ow of waste products of combustion generated in the boiler.

rality of individual ice-freezing sections each of which is mounted in heat exchange relationship at a plurality of points with a body of material to be frozen, means for directing the liquid refrigerant supplied to said evaporator into a selected one of said evaporator sections, thermostatic means foroperating said directing means, and

means operated in'response to demand for refrigeration within parts of the said body of material to be frozen whichare in heat exchange relationship with said evaporator sections for .allowing or preventing heat exchange between said thermostatic means and waste heat from` said boiler. I

3. Absorption refrigerating apparatus including anevaporator having a plurality of sections each of which is in heat exchange relationship at a plurality of points with a body of material to be frozen, liquid refrigerant vsupply means,

means for directing liquid refrigerant from saidY j supply means into a selected vone of said evaporator sections, thermostatic means for controlling'saiddirecting means, and refrigeration de mand responsive means for allowing or preventing actuation of' said thermostatic means by waste' heat from said refrigerant supply means.

4. Refrigerating apparatus including an element from which warm'gas is discharged, an evaporator having a plurality of individual freezing sections, liquid refrigerant supply means, thermostatic means .for directing liquid refrigerant from said supply means into4 a selected one of said evaporator sections, and refrigeration 'de' mand responsive means constructed and arranged to allow or to prevent heat exchange between said warm gas and said lthermostatic means to control said diverting means.

5. An absorption refrigerating apparatus of the type utilizing a boiler and a combustible fuel burner therefor, an evaporator comprising a first-freezing element, a rst space cooling element, a second freezing element, a second space cooling element, said elements being serially connected in the order named, means for propelling a pressure `equalizing medium through said elements serially in the order named, said system including liquid refrigerant supply means, and refrigeration demand responsive imeans operative to direct said liquid refrigerant wholly into either said first elements or said second elementsI as may be required.

6. Absorption refrigerating apparatus including a boiler, a combustible fuel burner for heat'- ing said boiler, a refrigerant vapor liquefying means, an evaporator comprising a plurality of sections each of which includes associated freezing and box-cooling elements, thermostatic means for directing liquid refrigerant from said liquefying means into a selected one of said sections, and refrigeration demand responsive for directing, or preventing flow of waste products of combustion from said fuel burner in heat transfer relationship with said thermostatic means. v v

7. Absorption refrigerating apparatus comprising liquid refrigerant supply means including a boiler, combustible fuel Burning means heating said boiler, refrigerant liquefying means, a first evaporator element including a freezing coil and a space cooling coil, a second evaporator element including a freezing coil and a space cooling coil, means for propelling apressure equalizing medium serially through said first and second evaporator elements, thermostatic means for directing liquid refrigerant from said liquefying means wholly into one or the other of said evaporator elements, a discharge flue having two branches constructed and arranged to convey wasteproducts of combustion from the boilerheater either in heat transfer relationship with said thermostatic means or directly to Waste, and refrigeration demand responsive means for governing said last-mentioned means.

8. Absorption refrigerating apparatus com-- prisingmeans forproducing refrigerant liquid including a heated element, means for heating said element, a plurality of evaporating elements,

means for directing liquid refrigerant generated by said apparatus to a selected one of said evaporating elements, and refrigeration demand re- 'sponsive means operative to allow 0r` to prevent the discharge of waste heat from said heating means into heat transfer relationship with said directing means.

9. Refrigerating apparatus comprising an evaporator including vertically spaced rear boxcooling conduits, forwardly projecting ice freez,

ing, evaporator sections, and forwardly projecting low temperature refrigerating evaporator conduits, all of said elements being serially con nected, liquid refrigerant supply means, and means for directing liquid refrigerant into a selected evaporator section.

10. Refrigeratin'g apparatus comprising a cooling unit including a pair of spaced box.

cooling sections, a pairy of U-shaped chilling sections each of which has one leg connected-to one of said box-cooling sections, one of said chilling 5 sections being connected to the other of said boxcooling sections, means for supplying a pressure equalizing medium to the chilling. section not connected to said other box-cooling section, and means for selectively supplying refrigerant to the pressure equalizing medium inlet portions of said chilling sections.

- 11. Refrigerating apparatus comprising a refrigerant supply means including a boiler anda heater therefor, a plurality of evaporators, means for directing refrigerant from said supply means into a selected evaporator, thermostatic means for operating said directing means, and means for directing waste heat from said heating means into and out of thermal relationship with said thermostatic means.

12. Refrigerating apparatus comprising an evaporator including a pair of finned box-cooling coil elements, a pair of ice-freezing coil elements operatively associated with said box-cooling coil elements, liquid refrigerant supply means, and means for directing liquid refrigerant from said supply means into a selected portion of said evaporator to render only a selected box-cooling element and a selected ice-freezing element operative.

13. Refrigerating apparatus comprising a pair of cooling units, a water container in heat transfer relationship therewith, an insulated chamber; a cooling unit serially connected to each of said first-mentioned cooling units and mounted in 1 said insulated chamber, a finned space cooling unit serially connected to each of said rst mentioned cooling units, a finned space cooling unit serially connected to one of said second mentioned cooling units and refrigeration demand responsive means for supplying cooling medium to a selected group of said cooling units.

14. Absorptionf refrigerating apparatus comprising a solution circuit including a boiler and an absorber, a pressure equalizing medium circuit including. an evaporator and said absorber, a combustible fuel burner for heating said boiler, said evaporator comprising two units each of which includes .box-cooling, ice-freezing and low temperature refrigerating sections, means for supplying refrigerant vapor generated in said boiler to said evaporator in liquid phase, directing mean for directing such vrefrigerant liquid toa selected one of said units, a flue for waste products from said boiler having two branches, refrigeration demand responsive means for controlling the fiow of waste products of' combustion through said flue branches, and thermostatic actuating means for said directing means in one of said branches.

15. Refrigerating apparatus comprising a cool.v

ing unit including a pair of spaced box-cooling sections, a pair of U-shaped chilling sections each of which has one leg connected to one of said box-cooling sections, one of said chilling sections being connected to the other of said boxcooling sections, and means for supplying'a pressure equalizing medium and a cooling medium to said cooling unit.

16. Absorption refrigerating apparatus comprising a generator, a condenser, an evaporator and an absorber connected to form a refrigeratingsystem includinga plurality of Vpaths of ow of fluid, a combustible fuel burner arranged to 'heat said generator, means providing a plurality of paths of fiow of waste products from said fuel burner, uid flow control means in said system to control at least one of said paths of ow of fluid, thermostatic means for actuating said fluid rst chilling element, a second chilling element, a second space cooling element serially connected to said second chilling element, means for directing cooling medium from said source wholly into one of said rst elements or into one oi' said second elements and refrigeration demand lresponsive means for operating said directing means.

CURTIS C. COONS.

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