US2557750A

US2557750A - Temperature regulator for refrigerators

Info

Publication number: US2557750A
Application number: US734107A
Authority: US
Inventors: Graham S Mccloy
Original assignee: Westinghouse Electric Corp
Current assignee: CBS Corp
Priority date: 1947-03-12
Filing date: 1947-03-12
Publication date: 1951-06-19
Anticipated expiration: 1968-06-19

Description

June 19, 1951 G. s. MccLoY mpmm REGULATOR von mmmmroas Filed llarch f2. 1947 INVENTOR Gamm S. McCybY a z w WITNSES ATTORNEY Patented June 19, 1951 TEMPERATURE REGULATR FOR REFRIGERATOBS Graham s. Mccioy, springfield, Mass., assigor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application March 12, 1947, Serial No. 734,107

8 Claims.

This invention relates to refrigeration apparatus and more specifically to temperaturecontrolling devices for such apparatus.

It is an object of the invention to provide a novel temperature-regulating means for a chamber cooled by a mechanical refrigerating unit.

A further object of the invention is to maintain the desired temperatures in a low temperature compartment and in a higher temperature compartment of a refrigerator cooled by a single refrigerating unit which is controlled by a single thermostat. The desired temperature in the latter compartment is maintained in lspite of variations in the ambient temperature of the sulated food storage chamber I2 and the lower portion of which comprises a machine chamber I4. The food storage chamber I2 is divided by a horizontal, thermally-insulated partition I5 into a frozen food compartment I6 and a refrigerated compartment I8.

The frozen food compartment I6 is cooled to a temperature of about 0 F. by a primary refrigerating system II which comprises an evaporator I9 consisting of a conduit 20 located on the rear Wall of the frozen food compartment IB. The conduit 20 comprises a number of inclined passes 2|, 23, 25, 26, 21, 29 and 3|, and is supplied at one end with refrigerant liquid through a capillary tube 22 by a condenser 24 located in the cabinet II). The other end of the `conduit' 20 connects with an upper portion of a refrigerant header 33 in such a manner that liquid refrigerant entering the header 33 cannot return to the conduit 20. vA suction tube 28 connects the header 33 with a motor-compressor casing 30. The conduit 20 is preferably but not necessarily so narrow that refrigerant liquid iiows therethrough together with the refrigerant vapors, the liquid forming pistons which are pushed along by the vapor until vaporized.

A compressor 32, driven by an electric motor 34, is located in the casing 30 and withdraws refrigerant vapor therefrom through the compressor inlet 36, compresses the vapor, and forces it through a tube 38 into the condenser 24 wherein it is liquefied. The compressor 32 also lowers the pressure in the casing 30 and in the evaporator I9. A motor-driven fan 48 draws the ambient air of the refrigerator cabinet I8 through the condenser 24 to cool the latter. The lower portion of the casing 30 forms a sump 42 for a mineral lubricating oil 43. The refrigerant in the primary refrigerating system I'I is dichlorodiuoromethane, commonly known as F-12.

The refrigerated compartment I8 is cooled to a temperature of about 40 F. by a secondary refrigerating circuit 44 containing a volatile refrigerant and having an evaporative portion 46 located in heat-transfer relationship .with the storage compartment I8, and a condensive portion 48 located in heat-transfer relationship with the upper pass 3I of the evaporator I9.

The primary refrigerating system I'I is controlled by a thermostat 50 adapted to energize the electric motor 34 through a switch 52 in the electric power supply lines 53. The thermostat 50 comprises a temperature-sensitive bulb 54 located in heat-transfer relationship with pass 25 of the evaporator I9. The thermostat bulb 54 contains a volatile liquid, the vapor pressure of which is transmitted through the tube 56 to a metal bellows 58 which controls the switch 52 by means of an overcenter spring 68. The thermostat 50 starts the motor 34 whenever the pass 25 of the evaporator I9 rises above a predetermined temperature and stops the motor 34 when the pass 25 has been cooled to a second predetermined temperature below that of the first predetermined temperature. Such thermostats are well known in the art. During the idle periods of the refrigerating system I'I, the refrigerant liquid in at least the upper` passes 25, 26, 21, 29 and 3| vaporizes.

The impedance of the capillary tube 22 is such that when the room in which the refrigerator is located is at a medium temperature, such as '75 F., some of the condensed refrigerant liquid will accumulate in the condenser 24 shortly after the compressor 32 is started.' After a period of time, the condenser 24 will be heated by the hot refrigerant vapor entering it, its pressure will rise, and most or all of the accumulated refrigerant liquid will be forced from the condenser 24 through the capillary tube 22 into the evaporator I9. If the room is warmer than '15 F., the

condenser 24 will be heated to a higher temperature and the last-described action occurs more quickly after starting the compressor 32. If the room is colder than 75 F., the condenser 24 will remain cooler and the action will occur after a longer period of time after starting the compressor 32.

'I'he accumulation of the refrigerant liquid in the condenser 24 shortly after the compressor 32 is started reduces the rate at which the refrigerant liquid enters the evaporator I9 during this period so that the refrigerant liquid isv supplied to the evaporator I9 at a slower rate during this period when the temperature of the room in which the refrigerator Ill is located is low than when this temperature is high.

'I'he temperature of the room in which the refrigerator is located, also affects the rate at which the suction pressure in the evaporator I9 is decreased. In a warm room, this rate is low because the high pressure in the air cooled condenser 24 reduces the pumping capacity of the compressor 32. In a cold room, the rate is higher because the pressure in the condenser 24 is lower.

Operation The frozen food compartment I6 is maintained at a substantially constant temperature by the thermostat 58 as is well understood in the art. The temperature of the refrigerated compartment I8 is maintained at a substantially constant temperature in varying room temperatures by the apparatus described above and in a manner now to be described.

The secondary circuit 44 is arranged to cool the lower compartment to 40 F. when the temperature of the room in which the refrigerator is located is about '75 F. This is effected by choosing the proper vdegree of heat exchange between the portion 48 and the upper pass 3| of the primary evaporator I9. In such a room, the refrigerant liquid will rise to the pass 25 when the bulb 54 causes the switch 52 to open. During such operation, the condensive portion 48 of the secondary circuit 44 is cooled by the refrigerant vapor flowing through pass 3|. This vapor has been superheated in

passes

26, 21 and 29 and is consequently warmer than the refrigerant liquid in pass 25 on which the thermostatic bulb 54 is located.

If the room in which the refrigerator is located becomes warmer, the rate at which the condenser 24 supplies refrigerant liquid to the primary evaporator I9 increases and the rate at which the suction pressure on the evaporator I9 is lowered decreases. As a. consequence, the refrigerant liquid will enter pass 26 and perhaps also pass 21, depending onthe room temperature before the suction pressure on the refrigerant liquid in the evaporator I9 is lowered suiliciently to reduce the temperature of the liquid to the degree at which the bulb 54 opens the switch 52. In this case, the condensive portion 48 will also be cooled by the refrigerant vapor, but this vapor is colder than the corresponding vapor described in the previous example because the vapor is not superheated to the same extent since it flows only through pass 29 and perhaps pass 21.

In a still warmer room, the refrigerant liquid will enter pass 3I lby the time the suction pressure in the evaporator I9 is reduced sufficiently to cause the bulb 54 to open the switch 52. In this case, the condensive portion 48 is cooled to the same temperature as the bulb 54. No superheat is present and the cooling of the condensive portion 48 is consequently more effective.

On the other hand, if the temperature of the room in which the refrigerator is located drops below '15 F., the reverse action occurs and the severity of this action will depend on the coolness of the room. Under such conditions, the refrigerant liquid will enter the evaporator I9 at a slower rate than in the '75 room, and the suction pressure on the evaporator I9 will be decreased more rapidly. The liquid in pass 23 will be so cold that it will cool the bulb 54 to the cutoff temperature as soon as it comes adjacent to it. In this case, the refrigerant vapor, which cools the condensive portion 48, will be at a much higher temperature because it is superheated in

passes

25, 26, 21 and 29.

It will be observed from the above that the condensive portion 48 of the secondary circuit 44 is cooled more effectively when the temperature of the room in which the refrigerator I0 is located is high, as compared to its action when the temperature is low. Consequently, the evaporative portion 46 will cool the refrigerated compartment I8 more effectively when the temperature of the room is high than when the temperature is low. This change in the rate of cooling the refrigerated compartment I8 offsets the varying rate of heat leakage into the refrigerated compartment I8 in varying room temperatures and tends to hold the temperature of the compartment I8 substantially constant.

While the invention has been explained with reference to a secondary volatile refrigerant circuit, such a circuit is not a necessary part of the invention since the higher temperature compartment I8 may be cooled directly by the last pass 3I of the evaporatonl by placing the pass 3| in the compartment I8.

It will be apparent from the above that this invention provides a means for holding the temperature of a refrigerant com-partment substantially constant in varying ambient temperatures.

While the invention has been shown in but one form` it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof.

What I claim is:

1. In a refrigerator comprising an insulated chamber, a refrigerant evaporator having a conduit including an entrance and an exit spaced from one another, a refrigerant circulating and liquefying apparatus including a compressor communicating with said exit for lowering the pressure in said conduit, withdrawing vaporized refrigerant therefrom, and compressing said vapor, a condenser receiving compressed refrigerant from said compressor to liquefy the same, and means for conducting liquid refrigerant from said condenser to the entrance of the conduit and impeding the flow of said liquid, the combination with said refrigerator of a thermostat for controlling said apparatus to maintain the temperature of said conduit at a point spaced from the exit thereof between predetermined temperature limits, said refrigerant circulating and liquefying apparatus being such that the rate of lowering of the pressure in said conduit, after said apparatus is started by said thermostat, decreases when the ambient temperature of the apparatus increases within the normal range of such temperatures, and a secondary refrigerating circuit having a heat-rejecting portion in heat-transfer relationship with a portion of said conduit located between said point and said exit, said circuit also having a heat-absorbing portion in heat-transfer relationship with said chamber.

2. In a refrigerator comprising an insulated chamber, a refrigerant evaporator having a conduit including an entrance and an exit spaced from one another, a refrigerant circulating and liquefying apparatus including a compressor communicating with :aid exit for lowering the pressure in said conduit, withdrawing vaporized refrigerant therefrom, and compressing said vapor, a condenser for receiving compressed refrigerant from said compressor to liquefy the same, and means for conducting liquid refrigerant from said condenser to the entrance of the conduit and for impeding the flow of said liquid, the combination with said refrigerator of a thermostat responsive to the temperature of said conduit at a point spaced from the exit thereof,

said thermostat being adapted to start said compressor when the temperature at said point rises to a predetermined temperature and to stop said compressor when the temperature at said point drops to a predetermined temperature below that of said first-named predetermined temperature, thereby producing an on cycle and an "01T cycle of said apparatus, said conduit being so arranged and the refrigerant charge being so proportioned that the conduit is substantially de-` void of refrigerant liquid during at least the latter portion of said off cycle, said refrigerant circulating and liquefying apparatus being so responsive to its ambient temperature, that, on being started by said thermostat, the rate at which said apparatus lowers the pressure in said conduit varies inversely with said ambient temperature within the normal range thereof, and a secondary refrigerating circuit having a heat-rejecting portion in heat-transfer relationship with a portion of said conduit located between said point and said exit, said circuit also having a heat-absorbing portion in heat-transfer relationship with said chamber.

3. In a refrigerator comprising an, insulated chamber, a refrigerant evaporator having a conduit including an entrance and an exit spaced from one another, a refrigerant circulating and liquefying apparatus including a compressor communieating with said exit for lowering the pressure in said conduit, withdrawing vaporized refrigerant therefrom, and compressing said vapor, a

condenser cooled by the ambient air of the chamber, said condenser receiving compressed refrigerant from said compressor to liquefy the same, and means for conducting liquid refrigerant from said condenser to th'e entrance of the conduit and A for impeding the flow of said liquid, the combination with said refrigerator of a thermostat responsive to the temperature of said conduit at a point spaced from the exit thereof, said thermostat being adapted to start said compressor when the temperature at said point rises to a predetermined temperature and to stop said compressor when the temperature at said point drops to a predetermined temperature below that of said first-named predetermined temperature, said refrigerant circulating and liquefying apparatus being so responsive to the temperature of the ambient air of said chamber that, on being started by said thermostat the rate at which said apparatus lowers the pressure in said conduit varies inversely with said ambient temperature within the normal range thereof, and a secondary refrigerating circuit having a heat-rejecting portion in heattransfer relationship with a portion of said conexit for lowering the pressure in said conduit. 1

withdrawing vaporized refrigerant therefrom, and compressing said vapor, a condenser cooled by the air ambient the chamber, said condenser receiving compressed refrigerant from said compressor to liquefy the same, and means for conducting liquid refrigerant from said condenser to the entrance of the conduit and for impeding the ilow of said liquid, the combination with said refrigerator of a thermostat responsive to the temperature of said conduit at a point spaced from both the entrance and the exit thereof, said thermostat being adapted to start said compressor when the temperature at said point rises to a predetermined temperature and to stop said compressor when the temperature at said point drops to a predetermined temperature below that of said first-named predetermined temperature, said refrigerant circulating and liquefying apparatus being so responsive to the temperature of the air ambient the chamber that, on being started by said thermostat, the rate at which said apparatus lowers the pressure in said conduit varies inversely with said ambient temperature within the normal range thereof, the portion of said conduit between said entrance and said poin't being adapted to cool one compartment of said chamber, and a secondary refrigerating circuit having a heat-rejecting portion in heat-transfer relationship with the portion of said conduit 1ocated between said point and said exit, said circuit also having a heat-absorbing portion adapted to cool the other compartment.

5. In a refrigerator comprising an insulated chamber divided into two compartments, a refrigerant evaporator having a conduit including an entrance and an exit, a refrigerant header at the exit of said passage, a compressor communieating with said header for lowering the pressure in said conduit, withdrawing vaporized refrigerant from said header, and compressing said Vapor, a condenser cooled by the air ambient the chamber for receiving compressed refrigerant from said compressor and liquefying the same, means for conducting liquid refrigerant from said condenser to the entrance of the conduit, and for impeding the flow of said liquid, a thermostat responsive to the temperature of a point on said conduit spaced from both the entrance and the exit thereof, said thermostat being adapted to start said compressor when the temperature of said point rises above a predetermined temperature and to stop said compressor when the temperature of said point drops to a predetermined temperature below that of said firstnamed predetermined temperature, said refrigerant circulating and liquefying apparatus being so responsive to the temperature of the air ambient the chamber that, on being started by said a. heat-rejecting portion in heat-transfer relationship with a portion of said conduit located between said point and said header, said circuit also having a heat-absorbing portion adapted to cool the other compartment of said chamber.

6. The refrigerating apparatus defined in claim wherein a portion of the refrigerant header is located below the level of the exit of said passage.

7. In a refrigerator comprising an insulated chimber having a first portion and a second portion, a refrigerant evaporator having a conduit including an entrance and an exit spaced from one another, a refrigerant circulating and liquefying apparatus including a compressor communicating with said exit for lowering the pressure within said conduit, withdrawing vaporized refrigerant therefrom, and compressing said vapor, a condenser receiving compressed refrigerant from said compressor to liquefy the same, and

means for conducting liquid refrigerant from said condenser to the entrance of the conduit and impeding the ow of said liquid, the combination with said refrigerator of a thermostat for controlling said apparatus to maintain the temperature of the conduit at a point spaced from the exit thereof between predetermined temperature limits, said refrigerant circulating and liquefying apparatus being such that the rate of lowering of the pressure in said conduit, after said apparatus is started by said thermostat, decreases when the ambient temperature of the apparatus increases within the normal range of such temperatures, said conduit having a first portion between said entrance and said point arranged for cooling said rst portion of said chamber, and means including a second portion of said conduit between said point and said exit for cooling said second portion of said chamber.

8. In a refrigerator comprising an insulated chamber divided into two compartments, a refrigerant evaporator having a conduit including an entrance and an exit spaced from one another, a refrigerant circulating and lquefying apparatus including a compressor communicating with said exit for lowering the pressure in said conduit, withdrawing vaporized refrigerant therefrom, and compressing said vapor, a condenser cooled by the air ambient the chamber, said condenser receiving compressed refrigerant from said compressor to liquefy the same, and means for conducting liquid refrigerant from said condenser to the entrance of the conduit and for impeding the flow. of said liquid, the combination with said refrigerator of a thermostat responsive to the temperature of said conduit at a point spaced from both the entrance and the exit thereof, said thermostat being adapted to start said compressor when the temperature at said point f rises to a predetermined temperature and to stop said compressor when the temperature at said point drops to a predetermined temperature below that of said first-named predetermined temperature, said refrigerant circulating and liquefying apparatus being so responsive to the temperature of the air ambient the chamber that, on being started by said thermostat, the rate at which said apparatus lowers the pressure in said conduit varies inversely with said ambient temperature within a normal range thereof, the p0rtion of said conduit between said entrance and said point being adapted to cool one compartment of said chamber, and means including the portion of said conduit between said point and said exit for cooling the other compartment.

GRAHAM S. McCLOY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,246,551 Stickel June 24, 1941 2,315,460 Steenstrup Mar. 30, 1943 2,317,709 Alsing Apr. 27, 1943 2,339,944 Preble Jan. 25. 1944 2,345,714 Philipp Apr. 4, 1944 2,433,188 Kalischer Dec. 23, 1947