US2720757A - Two temperature refrigerating apparatus - Google Patents

Description

Oct. 18, 1955 J. H. HEIDORN 2,720,757

TWO TEMPERATURE REFRIGERATING APPARATUS Filed Jan. 4, 1952 @SFV 42 )j BRI f ll INVENTOR.

i FM MMM United States Patent C) TWO TENIPERATURE REFRIGERATING APPARATUS John H. Heidorn, Dayton, Ohio, assiguor to General Motors Corporation, Dayton, Ohio, a corporation of Delaware Application January 4, 1952, Serial No. 264,903

2 Claims. (Cl. 62-4) This invention relates to refrigerating apparatus and more particularly the type of household refrigerator in which the freezing compartment and its evaporating portion is thermally isolated from the food compartment and the food compartment is provided with a separate evaporating portion connected in series with the freezing evaporating portion.

in refrigerators of this type the refrigerating system operates at a sufficient low back pressure to maintain a low freezing temperature such as to 5 degrees Fahrenheit, at all times. The food compartment evaporating portion operates upon a defrosting cycle. The freezing compartment has sufficient mass to retain its low temperature during the defrosting of the food compartment evaporating portion.

lt is an object of my invention to so form the food compartment evaporator that it will provide, under these conditions, a standard, uniform temperature within the food compartment under room temperature conditions varying from 70 to llO degrees Fahrenheit while low freezing temperatures are maintained in the freezing compartment.

It is another object of my invention to so arrange the food compartment evaporator that all of it will be used actively under high room temperature conditions but at lower room temperature conditions the portion of the food compartment evaporator in active use will be limited.

lt is another object of my invention to arrange a plate type evaporator in such a way that under high refrigerating requirements the entire evaporator is actively refrigerated but under low refrigerating requirements only the peripheral areas are actively refrigerated.

To attain these objects l have provided a vertical rectangular refrigerant plate in the food compartment which has its inlet connected to the outlet of the freezing evaporating portion. This plate is of such size as to provide adequate refrigeration for the food compartment in a 110 degree room. To limit the refrigeration at lower room temperatures, I provide a vertical gas trapping accumulator between the inlet and outlet of a refrigerated plate whereby at lesser room temperatures liquid refrigerant will accumulate during the operating period to limit the amount of refrigerant passage which will be flooded with liquid refrigerant during the operating period of the system. This accumulator is arranged so that during the idle period trapped gas will force the liquid refrigerant out of the accumulator and passages back into the freezing evaporating portion.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings, wherein a preferred form of the present invention is clearly shown.

In the drawing:

The figure is a vertical sectional view of a household refrigerator having thermally isolated freezing and food compartments.

Referring now to the drawing there is shown a refrigerator cabinet provided with a freezing compartment 22 adapted to be closed by a separate door and a food compartment 24 beneath the freezing compartment which may be closed by an outer door. In the specific construction, there is provided a standard food compartment liner 26. Between this standard liner 26 and the outer shell 28 Of the cabinet there is provided insulating means 39 which may be in the form of sealed bags of polyethylene containing glass or mineral wool.

The freezing compartment 22 is provided with a boxshaped inner sheet metal casing 32 upon the exterior surface of which there is provided refrigerant tubing 34 constituting the freezing portion of the primary evaporator system. Surrounding the inner casing 32 and the primary freezing tubing 34 is insulation 36 which is enclosed within a sealed metal outer container 38 fitting directly within the top portion of the liner 26 as shown in the ligure. The freezing evaporator tubing 34 is supplied with liquid refrigerant from a refrigerant'condensing unit which includes a sealed motor compressor unit 40 for compressing refrigerant and forwarding the compressed refrigerant to the condenser 42 where it is liquefied and forwarded through the capillary restrictor tube supply conduit 44 to the inlet of the tubing 34.

The outlet of the tubing 34 is provided with a trap portion 46 for preventing the draining of liquid refrigerant from the freezing evaporator tubing 34. This trap portion is connected by the conduit 48 to the inlet 50 of the vertically mounted rectangular refrigerated plate evaporator 52 spaced about an inch away from the upper portion of the rear wall of the liner 26, several inches below the bottom of the casing 38 of the freezing compartment 32. The refrigerated plate 52 is provided with a refrigerant passage 54 extending from the inlet 50 across the peripheral portion of the plate 52 and connecting with a downwardly extending passage 56 extending down the left side of the plate 52 and connecting with a passage 58 extending across the bottom of the plate 52.

ln accordance with my invention, adjacent the right edge of the plate 52 I provide a vertical accumulator 60 of sufficient size to trap a considerable portion of the liquid refrigerant in the system. The top of this accumulator 60 is provided with a gas trapping down wardly extending passage 62 which connects to a horizontal passage 64 extending across the mid-portion of the plate 52 which at its opposite end connects to a second, but larger, centrally located horizontal passage 66 extending generally horizontally but slightly inclined upwardly to the outlet portion 68 of the plate 52. This outlet portion 68 connects to the suction return line 70 connecting to the inlet of the sealed motor compressor unit 40.

At the bottom of the food compartment liner 26 there are provided two ventilated vegetable drawers 72 and 74. To keep these drawers at a sulliciently low temperature there is provided a secondary refrigerant circuit, including an evaporating portion 76 in the insulation space immediately below the bottom of the food compartment liner 26. The evaporating portion 76 is connected by tubing to a condensing portion 76 in the form of an inclined tubular member clamped to the back surface of the plate S2 in the position shown in the ligure with the top portion adjacentthe passage 64 in the bottom portion adjacent the passage S8.

The system is controlled by a thermostatie switch 80 operating upon a defrosting cycle. This switch is connected in series with the electrical conductor 82 which supplies electrical energy to the motor compressor unit 40. The switch 86 is of the snap-acting type operating on a defrosting cycle and is preferably set to close at a ten-1- perature of about 34 to 36 degrees Fahrenheit and to open at temperatures of about 0 to 5 degrees Fahrenheit. It is provided with a thermo-.sensitive element in the form of a capillary tube having itsrend portion 84 provided Vwith a serpentine shape and clamped, by the clamp 86,

to the back surface of the refrigerated plate 52 immediately beneath the accumulatorA 60 as shown inthe figure.

The refrigeratedplate 52 Yis made of such size that when approximately filled with liquid refrigerant under the cycles of refrigeration in a 110 degrees room, it will provide satisfactory temperature in the food compartment 24 While satisfactory low' temperatures are maintained inV thefreezing compartment 22. Under such operating conditions the portion 84 of the capillary tubing of the switch does noti reach the switch opening temperature until substantially the entire refrigerated plate 52 has been filled Y with liquid refrigerant and has been cooled to sucha low temperature that the food compartment 24 is adequately cooled. At lower roomltemperatures less refrigeration is needed for the food compartment since the heat leak is proportionately less from it than from the freezing compartment 22.' The vertical accumulator 60, under such conditions, limits the amount of refrigerant passage which is filled with liquid refrigerantY during normal cycling.Y Only the peripheral portions of the plate 52 are then Arefrigerated and the centrally located passages 64 and 66 are substantially free of liquid refrigerant.

When the defrosting temperatures of 34 to 36 degrees are reached, the refrigerated plate 52 has defrosted and is frost free. At this temperature the switch 80 closes and starts themotor compressor unit 40. This draws evaporated refrigerant from both the freezing evaporatingportion 34 and the'food compartment evaporating portion 52 and thereby causes an'initial surge in the ow of liquid refrigerant accompanied by violent boiling in the freezing portion 34 of the evaporator. This violent boiling carries some slugs of liquid along lwith the gas through the tubing into the plate 52. As the temperature of both evaporating portions decreases, the agitation decreases to the extent that more and more of the liquid remains trapped in the freezing evaporating portion 34. At the same time vgthefpressure is rising in the condenser 42 forcing more and more liquid into the freezing evaporating portion 34. lWhile this pressure isbuilding up, the supply of refrigerant is normally insuicient to provide a surplus for the refrigerated plate 52 so thatV it becomes starved of liquid, except perhaps for aV small'amount which may be trapped in the accumulator. During this time the temperature of the frozen food compartment is being lowered continuously at a relatively rapid rate.

. After the condenser 42 becomes warm and the condenser pressure is high, Ymore and more liquid refrigerant is fed to the freezing evaporating portion 34 so that it will'be a surplus of liquid refrigerant which is carried into the refrigerated plate 52. At rst this liquid refrigerant evaporates Vrapidly but as more and more is fed, the

plate is cooled down causing the liquid refrigerant toV extend further and further away from theV inlet 50 through the inlet passagesr54, 56 and 58. In cool room heat input into the food compartment. The refrigerant will over-flow the vertical accumulator 60 and reach Ythe passages 64 and 66 thereby providing refrigeration by the liquid refrigerant in the centralV portion of the plate 52. This increases the cooling capacity of the plate 52fto provide additional cooling for ll() degree room temperatures. to stop the refrigerant compressor the refrigerant-vapor will collect in increasing amounts in the top of the vertical accumulator 60 and force the refrigerant out of the refrigerant passage portions 58, 56 and 52, thencethrough the connecting conduit 48 back into the freezing vevaporating portion 34. Other portions of the liquid refrigerant may be forced through the refrigerant passage portions 64 and 66 into the suction line 70, but this-seldom takes place since in 1l() degree room temperature conditions this refrigerant will evaporate before it reaches` the suction line 70. Under lower room temperatures no refrigerant reaches the refrigerant passage` portion 66.

in this way the varying length of the operating aud idle periods of the motor compressor unit vary the temperatur@ such as degrees, the plate 90 will be Y Veach cycle and more and more refrigerant is accumulated in the vertical accumulator V60. The cooling of the food compartment 24' is 4then limited Vbecause the central portion of the plate 52 is not supplied with liquidV refrigerant.

Onlythe periphery is then supplied with liquid refrigerant. Y

, However, under warm room temperature'the plate 52 will not be cooled rapidly because of the much greater Vamount of refrigeration provided in accordance with the heat leak into the frozen food compartment 22. Because of Y its much lower temperature the heat leak into the frozen food compartment 22 is more constant because there is less percentage variation in temperature differential for various room temperatures. The providing of the vertical accumulator 60 at an immediate point in the series refrigerant passages in the refrigerated plate 52 by 1iimiting the surface contacted by the refrigerant providesV an additional reduction in refrigeration in the food compartment at colder room temperatures, since much lessV refrigeration is needed because there is a much greater percentage reduction in temperature differential for the food compartment as the room temperature is lowered. A'

In this way proper temperatures are maintained in both the freezing compartment 22 and the food compartment 24 under widely varying room temperature conditions.

The defrost water may be collected in a pan 73 located Y' in the machine compartment 75 where it may be evaporated by warm air currents.

While the form of embodiment of the'invention as.

herein disclosed constitutes a preferred form, it is to be understood that other forms might be adopted, as may Y orating means in heat exchange relation with said below Y freezing compartment and having its inlet connected to an outlet of said liquefying means, aV food compartment evaporating means in heat exchange relation with said food compartment and having its inlet connected to an' 'outlet of said freezing evaporating means, Vmeans for` returning evaporated refrigerant from said Yevaporating means to said liquefying means, said food compartment evaporating means including an upright plate having a series type refrigerant passagerextending adjacent the periphery and provided with a liquid trapping `accumulator. chamber at the end of said peripheral passage, said plate also having a passage in its central portion connected to the outlet of said accumulator chamber, and a thermostatic cycling control means having a thermosensitive element in Vheat exchange relation with the portionv ofV said plate adjacent the accumulator chamber of said upright plate for controlling the operation of said liquefying means.

2. Refrigerating apparatus including an above freezing food compartment and a belowfreezing compartment, l

a thermal heat transfer barrier between said` compartments, a refrigerant liquefying means, a freezing evap- Y orating means in heat exchange relation with said below freezing compartment and vhaving its inlet connected to WhenV the switch opening temperature is reached 5 an outlet of said liquefying means, a food compartment evaporating means in heat exchange relation with said food compartment and having its inlet connected to an outlet of said freezing evaporating means, means for returning evaporated refrigerant from said evaporating means to said liquefying means, said food compartment evaporating means including an upright plate having a series type refrigerant passage extending adjacent the periphery and provided with a liquid trapping accumulator chamber at the end of said peripheral passage, said plate also having a passage in its central portion connected to the outlet of said accumulator chamber, a secondary refrigerating system including a secondary evaporator arranged to cool said above freezing compartment and a secondary condenser contacting said plate ad- References Cited in the file of this patent UNITED STATES PATENTS 2,161,293 Heath June 6, 1938 2,291,559 Philipp July 28, 1942 2,484,588 Richard Oct. 11, 1949 2,578,906 Tobey Dec. 18, 1951

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