US2801525A

US2801525A - Two-temperature refrigerator with single evaporator

Info

Publication number: US2801525A
Application number: US503606A
Authority: US
Inventors: Harley H Bixler
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1955-04-25
Filing date: 1955-04-25
Publication date: 1957-08-06
Anticipated expiration: 1974-08-06

Description

H. H. BIXLER Aug. 6, 1957 TWOTEMPERATURE REFRIGERATOR WITH SINGLE EVAPORATOR Filed April 25, l955 2m m m ufrnx INVENTOR.

HARLEY H. BIXLER HIS JATTQRNEY' United States Patent TWO-TEMPERATURE REFRIGERATUR WITH SINGLE EVAPORATOR Harley H. Bixler, Louisville, Ky., assignnr to General Electric Company, a corporation of New York Application April 25, 1955, Serial No. 503,606

6 Claims. ((11. 62- 11) The present invention relates to a two-temperaturerefrigerator and particularly to a refrigerator comprising two compartments maintained at different operating temperatures by a single evaporator.

In the usual mechanical household refrigerator of the two-temperature type, refrigerant evaporator means are and reduces the elficiency f the cooling means, it is.

desirable that the frost layer be periodically removed.

One method for removing a frost layer from an evap orator comprises periodically raising the temperature of the evaporator above the freezing point of water for a time suflicient to melt the frost layer. This method, which is the basis for a number of automatic defrosting schemes, is quite satisfactory as applied to an evaporator employed only to cool the fresh food storage compartment where the normal temperature within this compartment is normally maintained above 32 F. However, a number of problems are involved in applying this method to the automatic defrosting of evaporators positioned in the freezer compartment due to the fact that the temperature of such an evaporator cannot be maintained at temperatures substantially above freezing for any appreciable period of time without damage to the frozen food stored in the compartment. For that reason, many of the present day two-temperature refrigerators are provided with two separate evaporators, one for each compartment, which evaporators are separately defrosted by manual or automatic means. For example, the freezer evaporator may be defrosted by placing trays of warm water on the refrigerated surfaces after first removing the contents of the freezer.

compartment. In order to obtain automatic defrosting of an evaporator serving the freezer compartment it has been found necessary to provide special heating means which will quickly raise the temperature of the freezer evaporator to a temperature such that the frost will melt from the evaporator within a short period of time and before the frozen foods are injured. Regardless of the defrosting means employed, refrigerators comprising two evaporators and separate automatic defrosting means for the two evaporators are both complicated and expensive while manual defrosting is, of course, time consuming and disagreeable. It is an object of the present invention to provide an improved refrigerator comprising a freezer compartment and a fresh food storage compartment and a single evaporator for cooling both compartments so constructed and arranged that the entire evaporator can be periodically raised to defrosting temperatures while maintaining both compartments at safe operating temperatures during the entire defrosting period.

A further object of the invention is to provide a twocompartment refrigerator including an improved simple and inexpensive automatic defrosting evaporator of the flooded recirculating type so arranged with regards to the "low temperature refrigerator compartment that the entire evaporator structure can be defrosted without materially affecting the temperatures Within the freezer compartment.

Another object of the invention is to provide a twotemperature refrigerator including a freezer compartment and a fresh food storage compartment and an evaporator of the flooded recirculating type adapted to maintain both of the compartments at the desired operating temperatures, the evaporator being so constructed and arranged that it can be periodically and automatically raised to defrosting temperature by the absorption of heat from the fresh food storage compartment without affecting the sub-freezing temperatures to be maintained inthe freezer compartment.

Further objects of my invention become apparent as the following desciption proceeds and the features of novelty which characterize the invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

In carrying out the objects of the present invention,

there is provided a two-temperature refrigerator comprising an upper freezer compartment and a lower fresh food storage compartment separated by an insulating partition. A single evaporator of the flooded recirculating type is employed for cooling both of the compartments. The evaporator comprises a first or lower portion disposed in the fresh food compartment and a second or upper portion in series connection with the first portion and positioned above the partition outside the frozen food compartment. In order to maintain the freezer compartment at temperatures below freezing, means are provided for circulating air from the freezer compartment over the upper evaporator portion and back through the freezer compartment.

For a better understanding of the present invention reference may be had to the accompanying drawing in which the single figure is an elevational and partially sectional View of a refrigerator incorporating an em bodiment of this invention.

Referring to the drawing there is shown a refrigerator cabinet 1 comprising an outer wall 2 and spaced inner walls defining a frozen food or freezer compartment 3 and a fresh food storage compartment 4. Both of the compartments are insulated from the outer wall 2 by in.- sulation 5 and from one another by an insulated partition 6. The access opening to the freezer compartment 3 is closed by a door 7 and the access. opening to the interior of the cabinet including both the freezer compartment 3 and the fresh food compartment 4 is closed by an insulated door 8. A machinery compartment 9 located in the lower portion of the cabinet structure contains the compressor unit 10. The machinery compartment is insulated from the fresh food compartment 4 by the insulating bottom wall 11.

In order to cool the freezer compartment 3 and the fresh food compartment 4, there is provided an evaporator 13 of the flooded recirculating type comprising a header 14 and a generally serpentine tubing 15. One end 16 of the tubing is connected to the header 14 below the normal refrigerant liquid level therein while the other end 17 is connected to the header above the normal liquid refrigerant level. By this arrangement liquid refrigerant flows from the header through the connection 16 into the tubing 15 while vaporized refrigerant is discharged into the header through the tubing outlet end 17.

The refrigerating portion or leg of the evaporator 13 includes a lower portion 20 which is arranged in a gen- I erally sloping plane within and adjacent the upper end of the fresh food compartment 4 for maintaining this compartment at the desired fresh food storing temperatures. Asecond serpentine portion 21 f the tubing is positioned Within a duct 21-abovethe partition 6 and outside the freezer compartment fi. The duct 22has an inlet 23 in the rear wall 24 of the freezer compartment 3 and an outlet 25 in the bottom wall 26 of the freezer compartment 3 adjacent the door 7 closing the access opening to this compartment. A fan 27 driven bya motor 23 and positioned within the duct 22 adjacent the aperture 23 periodically withdraws air from the freezer compartment 3 and passes it in heat exchange relationship with the evaporator-portion lfandback into thefreezer compartment 3 through the inlet 25'. Thisair cooled by the upper evaporatorportion 21 maintains the contents of the freezer compartme11t3 at sub-freezingtemperatures. A lip/3i along-the forward-edge of the bottom wall 26 of the freezer'compartment adjacent the-bottom of the do'or7 directs the airissuingfrom the inlet 25 rearwardly. of the compartment 3 and aids-in preventing' tion 21 with the vaporized refrigerant flowing back to the header 14 through the upper tube connection 17. The 'vaporizedrefrigerant is withdrawn from the header 14 by the compressor through the suction line 34. The compressed refrigerant iscondensed in the condenser 35 and liquid refrigerant'from the condenser is introduced through thecapillary as and the injector 37 into the lower portion 2t? of the evaporator. The injector 37 is so arranged that the injected liquid refrigerant fiows into the evaporator in the same direction as the normal circulation of liquid refrigerant through the tubing 15.

The operation of both the fan motor 28 and the compressor 10is under the control of a temperature responsive control element 40 which senses the temperatures within the fresh food storage compartment 4 and auto matically energizes the compressor and the fan 28 whenever the temperatures within this compartment rise above a predetermined rnaximum, as for example about 40 F. By synchronizing the operation of'the fan and compressor, air is circulated to the freezer compartment 3 only dur ing the compressor on cycle and hence only when the evaporator portion 21 isat sub-freezing temperatures.

In order to maintain the required temperatures within the two compartments 3 and 4, particularly the freezer compartment 3, it is necessary that the entire evaporator normally operate at a temperature somewhat below the freezing point of water. As a result, moisture in the air within the two storage compartments condenses on the evaporator portions and collects thereon as frost. This frost layer acts as an insulating medium, reducing substantially the cooling effect of the evaporator and therefore reducing the efficiency of the entire refrigerating system; It is desirable therefore to remove this blanket of frost from time to time in order to maintain the operation of the system at a reasonably high efficiency. The construction and arrangement of the evaporator forming part of the present invention makes possible the periodic removal of this frost layer by the melting thereof without materially increasing the temperature of the contents of the freezer compartment 3.

In order to remove the frost layer, the entire evaporator 13 isperiodically raised to a temperature somewhat above the melting point of ice. While any suitable source of heat may be employed, in the form of the invention illustrated the heat required for the defrosting operation is obtained from the air within the fresh food storage compartment 4 which normally is at temperatures somewhat above freezing. More specifically during each of the compressor off cycles and while the fan 27 is not operating, heat exchange between the lower evaporator portion 29 and the air within the storage compartment 4 is employed for warming of the lower portion to a temperature somewhat above the freezing point of water to melt the frost layer on the lower portion 20.

As a result of the warming of the lower portion 20 of the evaporator 13 some of the liquid refrigerant in this portion is vaporized resulting in a natural circulation of the liquid and vaporized refrigerant upwardly through the connecting portion 32 and the upper portion 21 of the tubing 15 where the warm refrigerant then melts the frost layer on these portions to obtain-a complete defrosting of the entire evaporator tubing 15. The melted frost from the upper evaporator portion zl collects in a trough 49 positioned-in thelowerportion of the duct 22. The trough 49 is preferably incontact with a single pass 32a of the evaporator intermediate portion32 to melt any frost or ice collecting in the trough. From the trough,

the water flows through a drain tube 50 into the trough.

44 within the fresh food storage compartment. The melted frost or condensate from the evaporator portion 24 collects on the baffie 43 and also drains into the trough 44 from which the condensate from both evaporator portions flows down a corner of the storage compartment 4 and outwardly through a drain tube 45 provided in the bottornof the storage compartment. This moisture collects in a drip pan 46 in heat exchange relationship with the compressor it where it is evaporated by the heat from the compressor.

By this arrangement the automatic defrosting of the evaporator 13 is obtained during each of the off cycles or idle periods of the refrigerating system. Since none of the evaporator is in direct heat exchange relationship with the interior of the freezer compartment 3 or more specifically with the contents thereof, the entire defrosting operation can be carried out without materially affecting the temperature of the freezer compartment 3. By controlling the operation of both the fan motor 28 and the compressor 10 by means of the same switch 40, there is no possibility of the fan 27 circulating air through the freezer compartment 3 and over the defrosting or defrosted evaporator 21 during the periods when the compressor 10 is not operating and the automatic defrosting operation is taking place. Preferably the evaporator 13 including thefreezer portion 21 should have a low thermal masstopermit rapid defrosting thereof during the off cycle while the freezer compartment 3 should have sufficient thermal mass to prevent any substantial increase in the temperature thereof during the defrosting periods.

Wherever the control40 within the storage compartment 4'again calls for refrigeration, a lowering of the refrigerant pressure within the header 14 by the operation of the compressor 10 and the introduction of fresh liquid refrigerant into the evaporator through the injector 37 quickly lowers the temperature of the entire evaporator to below freezing. Cooling of the air within" the lower fresh food storage compartment 4- is'then' again obtained by convection, i. e; by the naturalcirculation of the air upwardly along'the front ofthis compartment into contact with the evaporator portion 20 and downwardly along the rear wall thereof. As the fan 27 is also operating, airiswithdrawn from the freezer compartment 3 and after being cooled to sub-freezing temperaturesby contact with the finned evaporator portion 21 is again introduced into the freezer compartment 3 to maintain the sub-freezing temperature of the contents thereof. When the compartment 4 again reaches a predetermined minimum temperature, the control 40 opens both the compressor and fan fhotor circuits whereupon the evaporator undergoes another defrosting cycle to remove the frost which has accumulated thereon during the on cycle.-

Since frost and moisture has a tendency to migrate within any given space to the coldest portion thereof the freezer compartment 3 and particularly the walls thereof also tend to remain frost free. During each operation of the blower 27 moisture within the compartment 3 which would otherwise form frost within that compartment, is withdrawn by the fan and condenses on the evaporator portion 21 which is of course the coldest point in the freezer compartment air circulating system.

While it is preferred that all of the heat required for the defrosting of the evaporator tubing 15 be obtained from the air within the fresh food compartment 4 it is obvious that auxiliary heaters or heating means could also be employed. Such auxiliary heating means could be placed, for example, in contact with the lower portion 20 of the evaporator structure in order to accelerate the natural circulation of the liquid and vaporized refrigerant through the recirculating evaporator during the defrosting operation. It is also obvious that such a heater or additional heating means would preferably be electrically interconnected with the electrical control system so that additional heat is supplied to the evaporator only when required for the defrosting thereof.

While a specific embodiment of this invention has been shown and described, it is not intended that the invention be limited to the particular construction shown and described and it is intended by the appended claims to cover all modifications within the spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A refrigerator comprising a cabinet including an insulating partition dividing said cabinet into an upper frozen food compartment and a lower fresh food compartment, means for cooling both of said compartments comprising a flooded recirculating evaporator including a header, a lower portion positioned in said fresh food compartment and an upper portion in series connection with said lower portion positioned above said insulating partition and outside said frozen food compartment, conduit means connecting said lower portion to said header below the liquid refrigerant level therein and said upper portion to said header above the liquid refrigerant level therein for normal refrigerant circulation of refrigerant from said header through said lower portion to said upper portion whereby during defrosting of said evaporator by warming of said lower portion to defrosting temperature warmed refrigerant circulates through said upper portion to effect defrosting thereof, means for circulating air over said upper portion and through said frozen food compartment, and means for rendering said air circulating means inoperative during defrosting of said evaporator.

2. A refrigerator comprising a cabinet including an insulating partition dividing said cabinet into an upper freezer compartment and a lower fresh food compartment, a duct above said partition having an inlet and an outlet communicating with said freezer compartment, a flooded recirculating evaporator comprising a header and a. continuous tubing connected at both ends to said header, said tubing including a lower portion comprising a plurality of passes disposed in said fresh food compartment and an upper portion disposed in said duct above said inculating partition outside said frozen food compartment, means for circulating air from said freezer compartment through said duct and over said upper portion one end of said tubing being connected to said header below the liquid refrigerant level therein from supplying liquid refrigerant to said lower portion and the other end of said tubing being connected to said header above the liquid refrigerant level therein whereby warming of said lower portion to defrosting temperature effects circulation of warm refrigerant upwardly through said upper portion thereby effecting the defrosting of said upper portion.

3. A refrigerator comprising a cabinet including an outer walland a plurality of inner walls spaced from said outer wall and defining an upper freezer compartment and a lower fresh food compartment, an insulating partition between said compartments, said frozen food compartment having an access opening at the front end thereof, and a door closing said access opening, an air duct above said partition having an inlet communicating with the rear portion of said frozen food compartment and an outlet communicating with the forward end thereof adjacent the bottom of said door and including a lip portion for deflecting the flow of air from said duct in a rearward direction through said frozen food compartment, means for cooling both of said compartments comprising a flooded recirculating evaporator including a header positioned above said partition between said outer wall and said freezer compartment, a continuous tubing connected at both ends to said header, said tubing comprising a lower portion including a plurality of horizontally disposed passes in said fresh food compartment and upper portion including a plurality of horizontal passes disposed in said duct and connected in series with said lower portion, one end of said tubing being connected to said header below the level of liquid refrigerant therein for supplying liquid refrigerant to said lower portion, the other end of said tubing being connected. to said header above the liquid level of refrigerant therein for conveying vaporized refrigerant from said upper portion to said header whereby periodic warming of said lower portion to defrosting temperatures effects a flow of warmed refrigerant upwardly through said intermediate and upper portions to defrost said upper portion, means for collecting defrost water from said upper portion and conveying said water to said fresh food compartment, and means within said duct for circulating air over said upper portion of said tubing and through said frozen food compartment.

4. A refrigerator comprising a cabinet including an outer wall and a plurality of inner walls spaced from said outer wall and defining an upper freezer compartment and a lower fresh food compartment, an insulating partition between said compartments, said frozen food compartment having an access opening at the front end thereof, and a door closing said access opening, an air duct above said partition having an inlet communicating with the rear portion of said frozen food compartment and an outlet communicating with the forward end thereof adjacent the bottom of said door and including a lip portion for deflecting the flow of air from said duct in a rearward direction through said frozen food compartment, means for cooling both of said compartments comprising a flooded recirculating evaporator including a header positioned above said partition between said outer wall and said freezer compartment, a continuous tubing connected at both ends to said header, said tubing comprising a lower portion including a plurality of horizontally disposed passes in said fresh food compartment and upper portion including a plurality of horizontal passes disposed in said duct and an intermediate portion including at least one horizontal pass connecting said lower and upper portions in series and being positioned in said duct below said upper portion, one end of said tubing being connected to said header below the level of liquid refrigerant therein for supplying liquid refrigerant to said lower portion, the other end of said tubing being connected to said header above the liquid level of refrigerant therein for conveying vaporized refrigerant from said upper portion to said header whereby periodic warming of said lower portion to defrosting temperatures effects a flow of warmed refrigerant upwardly through said inter mediate and upper portions to defrost said. upper portion, means including a trough in heat exchange relationship with said intermediate portion for collecting defrost W3:

7 ter from said upper portion'andconveyingsaidwater to said freshfoodcompartment," and meanswithin said duct'for circulating air over said upperportion of said tubing and through said frozen food compartment.

5. A refrigerator comprising a cabinet including an outer wall and a plurality of inner walls spaced from said outer wall and defining an upper freezer compartment and a'lower fresh food compartment, an insulatingpartition between said compartments, an air duct above said partition having an inlet communicating with'therear por-' tion of said frozen food compartment and an outlet communicating with the forward end thereof, means for cooling both of said compartments comprising a flooded recirculating evaporator includinga'header positioned above said partition between said outer walland saidfreezer compartment, a continuoustubing connected at both ends-to said header, said tubing comprising a lower portion including a pluralityof horizontally disposed passes in said fresh food compartment and upper portion in series connection with said lower portion and including a plurality of horizontal passes disposed in said duct, one end of said tubing being connected to said header below the level of liquid refrigerant therein for supplying liquid refrigerant to said lower portion, the other end of said tubing being connected to said header above the liquid level of refrigerant therein for conveying vaporized refrigerant from said upper portion to said header whereby periodic warming of said lower portion to defrosting temperatures effects a flow of warmed refrigerant upwardly through said intermediate and upper portions to defrost said upper portion, means within said duct for circulating air over said upper portion of said tubing and through said frozen food compartment, means including a compressor for withdrawing vaporized refrigerant from said header-and supplying liquid refrigerant to said evaporator, and means responsive to the temperature Within said fresh food compartment for controlling the operation of said compressor and said air circulating means.

6. A refrigerator comprising a cabinet including an outer wall and a plurality of inner walls spaced from said outer wall and defining an upper freezer compartment anda lower fresh food compartment, an insulating partition between said compartments, an air duct above said partition having an inlet communicating with the rear por-tion of saidfrozenfood compartment=and"an" outlet communicating with'th'e forward'endthereof, means for" cooling-both or said compartments comprising a flooded recirculating evaporator including aheader positioned above said partition between said outer wall and said freezer compartment, a continuous'tubing' connected'at' both-ends to said header, said tubing comprising 'a lower portion including a plurality of horizontally disposed passes in said fresh food compartment and'upper portion serially connectedto said lower portion and including a. plurality of horizontal passes disposedin said duct, one

end of said tubing being connected to said header below the level of-liquid refrigerant therein for supplyingliquid.

refrigerant to said lower portion, the other end of said tubing being connected to said'header above the liquid.

level of refrigerant therein-for conveying vaporizedrefrigcrant from said upper portion to said header fan means within said duct for-periodically circulating air over said References Cited in the file of this patent UNITED STATES PATENTS 2,133,956 Buchanan Oct. 25, 1938 2,167,036 Baker July 25, 1939 2,481,616 Richard Sept. 13,.1949' 2,589,551 Iwashita Mar. 18, 1952' 2,593,370 Warren Apr. 15, 1952 2,647,375 Zearfoss Aug. 4, 1953 2,728,203 King Dec. 27, 1955