US2133961A - Refrigeration apparatus - Google Patents

Description

- Patented Oct. 25, 1938 UNITED STATES REFRIGERATION APPARATUS Leslie B. M. Buchanan, Springfield, Mass, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application November Il, 1936, Serial No. 110,202

14 Claims.

My invention relates to refrigeration and. has for an object to provide animproved method and apparatus for refrigerating first and second zones of a refrigerator to relatively high and low refrigerating temperatures.

A further object of my invention is to provide an eflicient refrigerating machine 'having relatively high and low temperature cooling elements wherein the periods of time during which the machine operates to refrigerate the low temperature element is reduced by the utilization of refrigeration produced more efiiciently at higher temperature.

A still further object of my invention is to abstract heat from the condensed refrigerant supplied to the low temperature-element of a refrigerator by subjecting it to the zone cooled by the higher temperature element thereof.

These and other objects are effected by my invention as will be apparent from the following description and claims taken in connection with the accompanying drawing,-forming a part of this application, in which: I 1

Fig. 1 is a diagrammatic view of a two-temperature refrigerating machine arranged in accordance with'my invention; and

Fig. 2 is a modified view of a detail employed in the system shown in Fig. 1.

Reference will now be had to Fig. 1 of thedrawing wherein the numerals Ill and l I indicate zones or chambers to be refrigerated at relatively low and high temperatures, respectively. Evaporators i2 and I3 are disposed for cooling the air in the low and high temperature zones l and II, the evaporator l2 preferably including shelf portions 14 for supporting trays l5 in which a fluid to be congealed may be disposed. Refrigerant vaporized in the evaporators l2 and i3 is condensed by a condensing unit, generally indicated at l6 and including a compressor l'l, preferably driven by a motor I8, and a condenser 19, cooled in any suitable manner, such as, for example, by a fan 2|. I

While my invention is applicable to various forms of two temperature refrigerating machines, I have chosen to show it applied to a machine of the type shown and claimed in my copending application, Serial No. 15,003, filed April 6, 1935, and assigned to Westinghouse Electric 8: Manufacturing Company. The construction and oper-.

ation of this type of two temperature refrigerator will now be described.

Liquid refrigerant from the condenser l9 flows into a reservoir 22 having-outlets 23 and 24 disposed at different levels, the former of which is controlled by a valve 25 operated by a solenoid.

26 in such manner that the valve 25 is open when the solenoid 25 is energized and, conversely, it is closed when the solenoid 26 is deenergized. Refrigerant discharged from either outlet 22 or 24 passes to a conventional high side float valve 21 through a conduit 28 and thence to the evaporator l2 through a conduit 29.

The evaporators I 2 and 'I3 are connected by a from the evaporator l3: The foregoing defines a two-temperature refrigerating system in which vaporization in either evaporator may be selec*-' tively effected by varying the effective charge of refrigerant in the system, or, in other words, by varying the amount of refrigerant stored in the reservoir 22. 1

' When the evaporator I2 is effective for cooling the media in the zone ill, the valve 25 is closed so that refrigerant collects in the reservoir 22 to a depth determined by the outlet 24. The effective charge of refrigerant in the system or the amount of refrigerant circulated is reduced in an amount equivalent to the amount of refrigerant withheld from circulation in the reservoir 22.

At this time, the evaporator I2 is substantially filled with liquid refrigerant which flows thereto from the'reservoir 22 through the outlet 24, conduit 28, float valve 2l-and the conduit 29. Operation of the compressor ll produces a relatively low pressure in the evaporators l2 and I3 and vaporization of the liquid at low temperature is effected in the evaporator l2. The cold vaporized refrigerant passes through the conduit 3|, evaporator l3 and conduit 32 to the compressor.

A small amount of heat may be extracted from the air in the chamber II at this time by the gas which is superheated as it passes through the evaporator l3. I

Cooling of the chamber II is effected by opening the valve 25 whereby the withheld refrigerant in the reservoir 22 is released through the outlet 23 andvalve 25 to the conduit 28. Accordingly, the float valve is moved to its full open position to pass the stored refrigerant through the conduit 29 to the evaporator 12. The released refrigerant first fllls the evaporator l2 and then flows through the conduit 3! to the evaporator i3. The charge of refrigerant in the system is such that the evaporator li is'substantially filled when the reservoir 22 is empty or during periods when the full charge is.available for circulation.

Admission of liquid refrigerant to the relatively warm evaporator l3 effects rapid vaporization with an increase in pressure over that prevailing when the low temperature evaporator I2 is refrigerated.

vaporization is effected in the evaporator l3 at relatively high temperature and pressure by the operation of the compressor l1. As the low temperature evaporator- I2 is filled with liquid which defines a seal, refrigerant vaporized in the evaporator I3 is prevented frompasslng to the low temperature evaporator l2 and condensing therein, whereby undesirable heating of the 4 higher temperature evaporator of a two temperature refrigerator is effected at higher efliciency than refrigeration of the lower temperature evaporator. I propose to increase the overall efficiency of a two temperature refrigerator by reducing the period of time that the machine operates to effect refrigeration less emciently at low temperature by utilizing refrigeration which was produced more efficiently at a higher temperature.

In accordance with my invention, the conduit 29 which supplies condensed refrigerant to the evaporators l2 and i3 is subjected directly, or indirectly, to the cooling effect of the higher temperature evaporator l3, whereby heat is abstracted from the condensed refrigerant by the higher temperature evaporator. When refrigerating the lower temperature evaporator l2, an increase in efficiency is obtained as the total heat in the condensed refrigerant admitted thereto is reduced in an amount equivalent to the amount of heat abstracted by the higher temperature evaporator. When refrigerating the higher temperature evaporator l3, the heat imparted thereto by the condensed refrigerant does not represent a loss as it would have to be ab? stracted anyway. The result of this method of operation is a reduction in the period of time that the compressor operates to refrigerate the low temperature element at relatively low efficiency and an increase in the period of time that it operates to refrigerate the higher temperature evaporator at relatively high efllciency for a given total heat load on the two evaporators. Accordingly, the overall efflciency is substantially increased.

Preferably, the "conduit 29 is secured directly to the evaporator l3, as shown at 33, for the transfer of heat from the condensed refrigerant, to the evaporator.

The conduit 29 may be secured in heat transfer relation with the suction conduit 32 as shown at 34 and with the conduit 3|, as shown at 35, whereby the efficiency of the system may be increased further. The heat exchanger shown at 34 effects precooling of the liquid prior to its admission to the heat exchanger 33 by transferring heat to the vapor in the suction conduit 32 as superheat. The heat exchanger at 35 functions to further cool the liquid admitted to the evaporator I2 when it is being refrigerated by subjecting the liquid to the cold vapor passing through the conduit 3|. The heat exchangers 35, 33, and 34 are connected in series and are arranged for counterfiow of the fluids conveyed therethrough.

It is desirable that the refrigerant contained in the conduit 29 be maintained in a liquid state in order that a high rate of heat transfer between it and the evaporator I3 is effected. Accordingly, a device 45, shown by way of example as a pressure actuated valve may be disposed in the conduit 29 adjacent the evaporator l2. The purpose of the device 45 is to maintain the refrigerant in the conduit 29 under suflicient pressure to substantially reduce vaporization of the refrigerant therein. The device 45 preferably includes a valve member 46 which is opened by the pressure of refrigerant in the conduit 29. A spring 41 opposes opening movement of the valve member 46 and determines the pressure of the refrigerant in the conduit 29. The bias of the spring is such that the pressure of the refrigerant in the conduit 29 is maintained at a' value somewhat below the pressure of the refrigerant in the condenser l9 and conduit 29 but high enough to preclude the vaporization of any substantial amount of refrigerant in the conduit 29.

Control of the operation of the compressor l1 and of the valve 25 may be effected automatically in accordance with the temperatures to be maintained in the chambers Ill and II. Accordingly, thermostats 36 and 31 may be disposed so that they are eil'ected by the temperatures to be maintained and arranged for controlling the energization of the motor I! and solenoid 26.. The source of power for the motor l8 and solenoid 26 is represented by line conductors L1 and L2. The thermostat 36 opens and closes a switch 38 for deenergizing and energizing the motor IS in response to predetermined low and high temperatures within the chamber Ill. The thermostat 31 includes a movable member 39 for connecting a plurality of contacts 4|, 42 and 43 ,when 'the temperature in the compartment attains a predetermined value and for disconnecting the contacts when the temperature is depressed to the desired value. The contact 42 is connected to the line conductor L2 and the contacts 4| and 43 are connected respectively to terminals of the motor l8 and solenoid 26; the opposite terminals of the motor l8 and solenoid 26 being connected to the line conductor L1. Ac-

cordingly, the solenoid 26 and motor iii are energized by the thermostat 31 when the temperature Other forms of thermostatic control may be employed, if desired, wherein the low temperature compartment is given preference when both compartments require cooling.

Operation The position of the various elements shown in the drawing indicates that both chambers ill and II are above the temperatures at which their respective thermostats close. Assume a rise in temperatureiin the low temperature zone III to the value at which the thermostat closes the, switch 38. Closure of the switch eflects energization of the motor l8 which initiates operation of the compressor. As the solenoid e28 is deenergized, the valve 25 is closed so that refrigerant is stored in the reservoir. Therefore, the amount of liquid refrigerant in the low side of the system is reduced and fills the evaporator l2, only.

Condensed refrigerant delivered to the reservoir 22 flows through the outlet 24 into the conduit 28 and float valve 21 and thence through the conduit 29 and device to the evaporator l2. Heat is abstracted from the condensed refrig erant in the conduit 29 by the evaporator l3 and the media cooled thereby, as described heretofore. vaporization of refrigerant is effected in the low temperature evaporator l2 and the pressure and temperature of the refrigerant therein is progressively decreased by the compressor I! The refrigerant vaporized in the evaporator l2 passes through the conduit 3|, evaporator l3 and conduit 32 to the compressor and is superheated as it abstracts heat from the condensed refrigerant.

Operation of the compressor i1 continues to reduce the pressure and temperature of the refrigerant in the evaporator l2 until the temperature of the media in the chamber In is depressed to the relatively low value at which the thermostat 36 opens the switch 38 and terminates operation of the compressor.

Assume the temperature vof the chamber ll rises to the value at which the thermostat 31 moves the bridging member 39 into engagement with its associated contacts 4|, 42 and 43. This evaporator operation effects operation of the compressor l1 and opening of the valve 25, as described heretofore. Refrigerant stored in the reservoir 22 is discharged through the outlet 23 to the conduit 28 and float valve 21, and thence through conduit 29 and the valve device 45 to the evaporator l2. The addition of the stored refrigerant to the low side of the system causes liquid refrigerant to overflow into the conduit 3| and a substantial portion of the evaporator l3.

The pressure in the entire low side of the system immediately increasesas the condensed refrigerant is admitted to the relatively warm evaporator I3 due to rapidevaporation. The compressor operates to progressively depress the pressure and temperature of the refrigerant in the i3. The heat transmitted to the evaporator l3 by the condensed refrigerant in the present instance represents neither a loss nor gain as this heat must be abstracted from the condensed refrigerant in any event. As the temperature of the chamber is depressed to the desired value the thermostat 31 operates to terminate operation of the compressor i1 and to close the valve 25.

- Assume now that the low temperature thermostat 36 closes to initiate operation of the compressor H. The evaporator l3'is filled substantially with condensed refrigerant from the previous cycle. -This refrigerant is first evaporated and is condensed and stored in the reservoir. 22. Some refrigeration of the chamber II is produced by this operation but the refrigerant is soon evaporated. As the pressure continues to be depressed, evaporation is effected in the low temperature evaporator l2 and continues until the thermostat 38 terminates operation of the com pressor I I as described heretofore.

In Fig. 2, I have shown another form of heat exchanger, generally indicated at 44, for effecting abstraction of heat from the condensed refrigerant. In this form, the liquid conduit 29 is subjected, directly, to the refrigerant in the high temperature evaporator l3. The employment of this form of heat exchanger is particularly desirable when the invention is applied to a two temperature system of the type shown in Fig. 1, as will be apparent from the following.

As described heretofore, the evaporator I2 is I filled, substantially with refrigerant when the thermostat 36 initiates operation of the compressor I! subsequent to previous cycle in which the evaporator i3 was operated. Accordingly, this refrigerant is evaporated with the starting of the compressor and abstracts heat from the media cooled by the evaporator l3 and from the condensed refrigerant in the conduit 29. By employing a heat exchanger of the type shown at 44 in Fig. 2, heat from the condensed refrigerant is more readily abstracted by the refrigerant in the evaporator l3 and less heat is removed from the media in the chamber which, of course, is advantageous as the temperature of the media is depressed less at this time.

.In the control disclosed, the warmer compartment l I is given preference when both the warmer and colder compartments require cooling, although the preference may be reversed, if desired.

' However, in any'event, the operation should be such that the temperature of the warmer compartment would be prevented from rising too high in order to obtain increased efliciency due to the exchange of heat above described.

From the foregoing, it will be apparent that I have provided an efficient two-temperature refrigerator wherein the periods of refrigeration at low temperature and relatively low efiiciency are reduced by the utilization of refrigeration pro duced at higher temperature and high efficiency.

I have shown a type of two-temperature re- I frigerating system wherein refrigeration of. the evaporators is selectively produced by varying the effective charge of refrigerant in the system,

7 but it will be understood that my invention is equally applicable to other forms of twotemperature systems whether the operation of the evaporators is selective or not.

While I have shown my invention in several forms, it will be obvious to those skilled in the art that it is not so limited,but is susceptible of various other changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

1. The method of refrigerating relatively high and low temperature evaporators, which comprises selectively effecting evaporation of refrigerant in the high and low temperature evaporators, condensing the vaporous refrigerant and returning it to the evaporators, and transferring heat from the condensed refrigerant at substantially condensing pressure to the high temperature evaporator.

2. The method of refrigerating relatively high and low temperature evaporators, which comprises effecting evaporation of refrigerant inithe high and low temperature evaporators, condensing vaporous refrigerant and returning it to the evaporators, and transferring heat from the condensed refrigerant at substantially condensing pressure to the refrigerant in the high temperature evaporator.

3. The method of refrigerating relatively high and low temperature evaporators, which comprises selectively effecting evaporation of refrigerant in the high and low temperature evaporators, condensing vaporous refrigerant and returning it to the. evaporators, and transferring heat from the condensed refrigerant at substantially condensing pressure to the refrigerant in the high temperature evaporator.

4. The method of refrigerating relatively high and low temperature evaporators, which comprises selectively effecting the flow of condensed refrigerant to the high and low temperature evaporators for vaporization therein and reducing the heat content of the condensed refrigerant at substantially condensing pressure by the utilization of refrigeration produced by the evaporation of refrigerant in the higher temperature evaporator.

5. The method of refrigerating relatively high and low temperature zones of a refrigerator which comprises supplying condensed refrigerant for vaporization at relatively low and high temperatures for cooling the low and high temperature zones, respectively, and reducing the heat content of the condensed refrigerant at substantially condensing pressurev by utilizing refrigeration produced by the refrigerant vaporized at relatively high temperature.

6. The method of refrigerating relatively low and high temperature evaporating elements, which comprises evaporating refrigerant in the low and high temperature evaporators at relatively low and high pressure, respectively, con-. densing the evaporated refrigerant, conveying the condensed refrigerant to the evaporators for vaporization, and transferring heat from the condensed refrigerant at substantially condensing pressure to the high temperature evaporator.

7. The method of refrigerating relatively low and high temperature zones of a refrigerator,

8. In refrigerating apparatus, the combination of relatively high and low ,temperature evaporators, means for condensing refrigerant evaporated in the evaporators, means for conveying condensed refrigerant to the evaporators for vaporization therein, and means for passing the condensed refrigerant at substantially condensing pressure in heat transfer relation with the refrigerant in the high temperature evaporator.

9. In refrigerating apparatus, the combination of relatively high and low temperature evapo-; rators, means for condensing refrigerant evaporated in the evaporators, means for conveying the condensed refrigerant to the evaporators for vaporization therein, and means for passing the condensed refrigerant at substantially condensing pressure in heat transfer relation with the high temperature evaporator.

10. In refrigerating apparatus, the combination of relatively high and low temperature evaporators, means for condensing refrigerant evaporated in the evaporators, means for conveying the condensed refrigerant to the high and low temperature evaporators for vaporization therein, and means for transferring heat from the condensed refrigerant at substantially condensing pressure to the high temperature evaporator.

11. In apparatus for refrigerating first 'and second zones of a refrigerator, the combination of relatively low and high temperature evaporators for respectively cooling the media in the zones, means for condensing at relatively high pressure the refrigerant vaporized in the evaporators, means for conveying the condensed refrigerant to the evaporators, and means for passing the relatively high pressure condensed refrigerant conveyed for vaporization in the low temperature evaporator in heat transfer relation with the media in the zone cooled by the high temperature evaporator.

12. In refrigerating apparatus, the combination of relatively high and low temperature evaporators, means for condensing refrigerant vaporized in said evaporators, means for conveying the condensed refrigerant to' the evaporators in such manner that it flows intothe low temperature evaporator until it is full and thence into the high temperature evaporator, means for selectively decreasing or increasing the quantity of liquid refrigerant in the evaporators so that when it is decreased liquid is evaporated in the low temperature evaporator while the high temperature evaporator is substantially dry and, when it is increased, liquid is present in said low temperature evaporator under sufficient pressure to prevent vaporization therein while liquid overflows into the high temperature evaporator and is evaporated therein, and means for transferring heat from the condensed refrigerant to the high temperature evaporator.

13. In refrigerating apparatus, the combination of relatively high and low temperature evap orators, means for condensing refrigerant vaporized in said evaporators, means for conveying the condensed refrigerant to the evaporators in such manner that it flows into the low temperature evaporator until it is full and thence into the high temperature evaporator, means for selectively decreasing or increasing the quantity of liquid refrigerant in the evaporators so that when it is decreased there is liquid being evaporated in the low temperature evaporator while the high temperature evaporator is dry and, when it is increased, there is liquid present in said low temperature evaporator under sufficient pressure to prevent vaporization therein while liquid overflows .into the high temperature evaporator and is evaporated therein, and means for transferring heat from the condensed refrigerant to the rev frigerant in the high temperature evaporator.

.14. In refrigerating apparatus, the combination of relatively high and low temperature evaporators, means for condensing at relatively high pressure the refrigerant vaporized in said'evaporators, means for selectively conveying the condensed refrigerant to the evaporators for vaporization and means for transferring heat from the relatively high pressure condensed refrigerant that is supplied for vaporization in the low temperature evaporator to the high temperature evaporator.

- LESLIE B. M. BUCHANAN.

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