Apparatus for controlling a 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) not in air flow communication with the freezer compartment (31). A refrigerator system is included having a 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 (41). 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).

Description: Background of the Invention The present invention relates to a refrigerator apparatus according to the first part of claim 1. Such refrigerator apparatus is known from US-A-3 026 688. 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 air delivered to both compartments to properly control the temperature in both compartments. In a refrigeration cycle having dual evaporators such as the one shown in copending application 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. Summary of the Invention According to the present invention, as claimed in claim 1, a refrigerator apparatus is provided including a freezer compartment, a fresh food compartment and a refrigerator system. The refrigerator system has a compressor, a condenser, a first expansion valve, a first evaporator situated in the freezer compartment, a second expansion valve, a second evaporator situated in the fresh food compartment. The refrigerator system elements are connected in series in a closed loop in a refrigerant flow relationship. A first fan is situated in the freezer compartment for providing air flow over the first evaporator. A second fan is situated in the fresh food compartment for providing air flow over the second evaporator. A first thermostatic controller is situated in the freezer compartment for maintaining a desired temperature in the freezer compartment by controlling the operation of the first fan. A second thermostatic controller is situated in the fresh food compartment for maintaining a desired temperature in the fresh food compartment by controlling the operation of the second fan. One of these controllers controls the operation of the compressor, the construction of the refrigerator apparatus being such that the remaining controller causes operation of that fan situated in the same compartment as said remaining controller only when said compressor is operating. 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: Figure 1 is a schematic representation of an embodiment of the dual evaporator refrigerator system with a control for controlling the relative cooling rates of the two evaporators; Figure 2 is a schematic representation of another embodiment of the dual evaporator refrigerator system with a control system; Detailed Description of the Invention Referring now to the drawing wherein like numerals indicates like elements throughout and more particularly Figure 1 thereof. 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 control 53 of the fresh food compartment is connected to one input of a logical AND gate 73 and the other input is provided from the other thermostatic control 51. The output of the AND gate 73 is connected to the fan 47. The thermostatic control 51 in the freezer compartment when above a preset temperature activates both compressors 65 and 67 and the fan 37 in the freezer compartment 31. The thermostatic control 53 in the fresh food compartment activates the fresh food fan when the temperature rises above its set point and the compressors are operating. When the compressors are operating and the fresh food thermostat is below its set point, the fan 47 in the fresh food compartment 41 is shut off because AND gate 73 is not enabled and cooling of the fresh food compartment 41 is stopped. The cooling rate produced by the evaporator 13 in the freezer compartment 31 is only minimally affected. System efficiency will decrease somewhat while the fresh food compartment fan 47 does not operate. Referring now to Figure 2, a dual evaporator two stage cycle is shown. The thermostatic control of the fresh food compartment 41 is connected to both motor controllers 61 and 63 and to fan 47 and causes both compressors 65 and 67 to operate as well as the fresh food fan 47 when the temperature of the fresh food compartment goes above a preset point. The thermostatic control 51 in the freezer compartment 31 is connected to one input of a logical AND gate 75 and the output of the fresh food thermostatic control 53 is connected to the other. The output of the AND gate is connected to fan 37. When the freezer compartments 31 temperature goes above a preset temperature, the fan 37 in the freezer compartment is operated if the compressors 65 and 67 are also operating. When the freezer evaporator fan 37 is not operating and the compressors are operating, cooling of the freezer compartment ceases, while continuing in the fresh food compartment 41. The cooling rate produced by the fresh food evaporator 25 is only minimally affected. System efficiency will decrease somewhat when the compressors are operating and the freezer fan 37 is not. The compressors shown do not have to be intercooled in order for the controls provided to regulate freezer and fresh food compartment temperature. Other intercooling techniques such as shown in copending application EP-A-0 374 688 can alternatively be used. The control shown in Figures 1 and 2 does not require a two stage compressor, only two evaporators one operating at temperature to cool the freezer compartment and one operating to cool the fresh food compartment. Providing air circulation between the fresh food and freezer compartments when the fresh food compartment temperature is above a predetermined set point would provide improved fresh food compartment temperature regulation. 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 having a first compressor (65), a condenser (21), a first expansion device (11), a first evaporator (13) situated in said freezer compartment, a second expansion device (23), a second evaporator (25) situated in said fresh food compartment, the refrigerator system elements connected in series in a closed loop in a refrigerant flow relationsship; a first fan (37) situated in said freezer compartment (31) for providing air flow over said first evaporator (13); a second fan (47) situated in said fresh food compartment (41) for providing air flow over said second evaporator (25); a first thermostatic controller (51) situated in said freezer compartment (31) for maintaining a desired temperature in said freezer compartment by controlling the operation of said first fan (37); a second thermostatic controller (53) situated in said fresh food compartment (41) for maintaining a desired temperature in said fresh food compartment by controlling the operation of said second fan (47) ; characterized by: one (51 or 53) of said controllers controlling the operation of said compressor (65), the construction of the refrigerator apparatus being such that the remaining controller (53 or 51) causes operation of that fan situated in the same compartment as said remaining controller only when said compressor is operating. The apparatus of claim 1, wherein said one and remaining controllers respectively are said first (51) and second (53) controllers. The apparatus of claim 1, wherein said one and remaining controllers respectively are said second (53) and first controllers (51). The refrigerator apparatus of claim 1, said apparatus further comprising a phase separator (27), said phase separator being connected in series between said second evaporator (25) and said first expansion device (11). The refrigerator apparatus of claim 1 further comprising: a second compressor (67) connected in series with said refrigerator system in a refrigerant flow relationship, and a phase separator (27) connecting said second evaporator (25) to said first expansion device (11) in a refrigerant flow relationship, said phase separator providing intercooling between said first and second compressors (65, 67); said one thermostatic controller (51 or 53) causing operation of both of said compressors.

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: F25D17, F25B5, F25D29, F25B1