Dual-evaporator, dual-fan refrigerator with independent temperature controls

Abstract: A refrigerator apparatus is provided having a cabinet with a freezer compartment (31) and a fresh food compartment (41). A refrigerator system is included having a first and second compressor (65;67), a condenser (21), a first expansion device (11), a first evaporator (13) situated in the freezer compartment (31), a second expansion device (23), a second evaporator situated in the fresh food compartment (4). The refrigerator system elements are connected in series in a closed loop, in a refrigerant flow relationship. A first fan (37) is situated in the freezer compartment (31) for providing air flow over the evaporator (13). A second fan (47) is situated in the fresh food compartment (41). A first thermostatic controller (51) situated in the freezer compartment (31) for maintaining a desired temperature in the freezer compartment by causing the compressor (65;67) and the first fan (37) to operate. A second thermostatic controller (53) situated in the fresh food compartment (41) for maintaining a desired temperature in the fresh food compartment by causing operation of the second fan (47). A phase separator (27) is connecting the second evaporator (25) to the first expansion device (13), said phase separator providing intercooling between the two compressors (65;67).

Description: Background of the Invention The present invention relates to a refrigerator having an evaporator in the freezer compartment and an evaporator in the fresh food compartment. The presently used refrigeration cycle in household refrigerators is the simple vapor compression type using a single evaporator. Relative cooling rates for the freezer and the fresh food compartments are controlled by the user. A user adjusted control, sets the fixed fraction of the total cold air flow provided by the single evaporator and fan which is to reach the two refrigerator compartments. When the temperature of the fresh food compartment rises above a preset level, the compressor operates allowing the evaporator to supply cold air. Since the fraction of cold air provided to the fresh food and freezer compartments does not vary once set, control of freezer temperature is imperfect and freezer air temperatures vary considerably. Changes in the ambient temperature, time defrosts of the freezer compartment, and changes of incidental thermal loads (door opening frequency and duration) requires time varying changes in the fraction of cold delivered to both compartments to properly control the temperature in both compartments. EP-A-0 374 688 (which is comprised in the state of the art in accordance with Article 54(3) EPC) shows a refrigerator apparatus comprising: a freezer compartment ; a fresh food compartment ; a refrigerator system including a first expansion valve, a first evaporator situated in said freezer compartment, a first and a second compressor, a condenser, a second expansion valve, a second evaporator situated in said fresh food compartment, all the above elements of the refrigerator system connected together in series, in that order, in a refrigerant flow relationship, and a phase separator connecting said second evaporator to said first expansion valve in a refrigerant flow relationship, said phase separator providing intercooling between said first and second compressors. In the refrigerator apparatus of EP-A-0 374 688, distinct cooling rates are provided by each evaporator during steady state operation. One evaporator operates at a temperature of approximately -23°C (-10°F) and the other at approximately -4°C (25°F) to provide cold air to the freezer and fresh food compartments, respectively. The cooling rates of the two evaporators depend entirely on heat exchanger and compressor designs, choice of refrigerant, ambient temperature, refrigerator cabinet thermal conductance and thermal loads other than conduction to the ambient. To provide separate and distinct narrow temperature ranges of operation in each of a refrigerators two compartments, provisions must be made to adjust the relative cooling rates of the two evaporators in response to changing ambient temperatures and incidental thermal loads. It is an object of the present invention to provide a control for regulating the cooling rates of a refrigerator equipped with a dual evaporator refrigerator system. Brief Description of the Drawing The subject matter which is regarded as the invention is defined in claim 1. The invention itself, however, both as to its organization and its method of practice, together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawing, in which the single Figure is a schematic representation of a dual-evaporator, two-stage refrigerator system with a control for controlling the relative cooling rates of the evaporators in accordance with the present invention. Detailed Description of the Invention Referring now to the drawing, a dual-evaporator, two-stage cycle with a control is shown. The dual-evaporator, two-stage system comprises a first expansion valve 11, a first evaporator 13, a first and second hermetically sealed compressor and motor 15 and 17, respectively, a condenser 21, a second expansion valve 23, and a second evaporator 25, connected together in that order, in series, in a refrigerant flow relationship by conduit 26. A phase separator 27 provides intercooling between the two compressors and comprises a closed receptacle having at the upper portion an inlet for admitting liquid and gaseous phase refrigerant and having two outlets. The first outlet is located at the bottom the receptacle and provides liquid refrigerant. The second outlet is provided by a conduit 29 which extends from the interior of the upper portion of the receptacle to the exterior. The conduit is in flow communication with the upper portion and is arranged so that liquid refrigerant entering the upper portion of the receptacle cannot enter the open end of the conduit 29. Two phase refrigerant from the outlet of the second evaporator 25 is connected to the inlet of the phase separator 27. The phase separator provides liquid refrigerant to the first expansion valve 11. The phase separator also provides saturated refrigerant vapor which combines with vapor output by the first hermetically sealed compressor and motor 15 and together are connected to the inlet of the second hermetically sealed compressor and motor 17. The first evaporator 13 contains refrigerant at a temperature of approximately -23°C (-10°F) during operation for cooling a freezer compartment 31. The evaporator 13 is situated in an evaporator chamber defined by walls 33 of the freezer and a barrier 35. A fan 37 situated between the evaporator chamber and the rest of the freezer compartment, when operating, draws air from the freezer into the evaporator chamber over the evaporator 13 and back into the freezer compartment 31. The second evaporator 25 contains refrigerant at a temperature of approximately -4°C (25°F) during operation for cooling the fresh food compartment 41. The evaporator 25 is situated in an evaporator chamber in the fresh food compartment 25 defined by walls 43 of the refrigerator compartment and a barrier 45. A fan 47 situated between the evaporator chamber and the rest of the fresh food compartment 41, when operating, draws air from the rest of the compartment across the evaporator and back to the compartment. A thermostatic control 51 is situated in the freezer compartment 31 and another thermostatic control 53 in the fresh food compartment 41. Both thermostatic controls are adjustable by the user. The thermostatic controller 53 in the fresh food compartment 41 is connected to the compressor motor controller 63 and fan 47 and controls the operation of the compressor 67 and the fan 47. The thermostatic controller 53 also provides one input to AND gate 77, with the output of the AND gate connected to motor controller 61 of compressor 65. The output of the AND gate 77 also controls the freezer fan 37. The thermostatic controller 51 of the freezer 31 when it rises above a preset temperature provides a logical "1" or high state to an inverting input of an AND gate 81. The output of AND gate 81 is connected to a timer 83 which when receiving a transitioning from the low to high state outputs a high signal for a predetermined length of time. The output of timer 83 is connected to the input of timer 85 which also provides a high output for a predetermined duration when triggered by receiving a signal transitioning from a low to a high state. The output of timer 83 is also connected to an inverting input of AND gate 77. An inverting input changes the logical state of the input signal before it is supplied to the AND gate. An inverting input acts as if a separate inverter receives the signal and then provides it to the AND gate. In operation,the fresh food thermostat 53 controls compressor 67 and fan 47. When the temperature in the freezer goes above a predetermined set point, a logical one signal is provided by the thermostat 51 to the inverting input of AND gate 81. The output of timer 83 when not operating, is at a low state which is connected to the inverting input of AND gate 77. When the fresh food thermostat is also above its set point, compressor 65 and fan 37 operate. When the freezer thermostat goes below a predetermined set point, a logical "0" signal is provided to one inverting input of AND gate 81. The timer 85, when not operating, has its output at a low state connected to the other inverting terminal of AND gate 81 enabling AND gate 81 and starting timer 83 which provides a high signal to one inverting input of AND gate 77 disabling AND gate 77 and compressor 65 and fan 37 do not operate. Timer 85 is triggered by timer 83 and disables AND gate 81 until timer 85 times out thereby controlling the time between subsequent shut downs of compressor 65 when compressor 67 is operating. When only one compressor is operating, refrigerant tends to accumulate in the phase separator 27 limiting the time during which one compressor operation can continue. Therefore, timer 83 determines how long single compressor operation occurs and timer 85 determines how long after timer 83 was first triggered it can be triggered again to allow single compressor operation to again occur. The foregoing has described a control for regulating the cooling rates of a refrigerator equipped with a dual evaporator refrigerator system.

Claims: A refrigerator apparatus comprising: a freezer compartment (31); a fresh food compartment (41); a refrigerator system including a first expansion valve (11), a first evaporator (13) situated in said freezer compartment, a first and a second compressor (65,67), a condenser (21), a second expansion valve (23), a second evaporator (25) situated in said fresh food compartment, all the above elements of the refrigerator system connected together in series, in that order, in a refrigerant flow relationship and a phase separator (27) connecting said second evaporator (25) to said first expansion valve (11) in a refrigerant flow relationship, said phase separator (27) providing intercooling between said first and second compressors (65,67); a first fan (37) situated in said freezer compartment (31) and directing air flow over said first evaporator (13); a second fan (47) situated in said fresh food compartment (41) and directing air flow over said second evaporator (25); a first thermostatic controller (53) situated in said fresh food compartment (41) and maintaining fresh food temperature by causing said first and second compressors (65,67) and said first and second fans (37,47) to operate when the fresh food compartment needs cooling; a second thermostatic controller (51) situated in said freezer compartment (31) and maintaining freezer temperature by interrupting operation of the first compressor (65) and the first fan (37) when the freezer compartment has been sufficiently cooled. The refrigerator apparatus of claim 1 further comprising timer means (83) for limiting the time during which just the second compressor (67) is operating. The refrigerator apparatus of claim 2 further comprising timer means (85) for controlling the time between sequential interruptions of the operation of the first compressor (65) while the second compressor (67) is operating.

Inventors: BESSLER WARREN FRANK, JASTER HEINZ, BESSLER, WARREN FRANK, JASTER, HEINZ
Applicants: GEN ELECTRIC, GENERAL ELECTRIC COMPANY
Application year: 1989
Main classification: F25D17
IPC codes: F25B1, F25D29, F25B5, F25D17