Patent Publication Number: US-9897364-B2

Title: High efficiency refrigerator

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 13/948,282, filed Jul. 23, 2013, entitled “HIGH EFFICIENCY REFRIGERATOR,” now U.S. Pat. No. 9,568,219, which is a continuation of U.S. Pat. No. 8,511,109, filed Jul. 15, 2009, entitled “HIGH EFFICIENCY REFRIGERATOR,” which are herein incorporated by reference in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     The present invention relates to a refrigerator including a freezer compartment and fresh food refrigeration compartment and particularly a thermal storage system for maximizing the efficiency of operation of the refrigerator. 
     Refrigerators typically cycle on and off depending upon the frequency of use, the content, and the surrounding environmental conditions. With conventional refrigerators, the refrigerator compressor runs at maximum capacity regardless of load demands. This results in the utilization of a significant amount of energy, which is environmentally wasteful and expensive for the consumer. Linear compressors, such as disclosed in U.S. Patent Publication 2006/00110259, the disclosure of which is incorporated herein by reference, are capable of a variable operating capacity ranging in the neighborhood of a ratio of 5:1. Linear compressors, thus, can be controlled to meet the actual demand for refrigerators but also have the benefit of begin capable of a higher operating capacity than conventional rotary compressors. Additionally, it is well known in the art that lowering condensing temperature increases efficiency of a refrigerant compressor, however, for the linear compressor disclosed in the referenced U.S. Patent Publication 2006/00110259, the capacity to compression work ratio can be amplified beyond that of a reciprocating compressor, thus providing a further favorable energy efficient operational condition. 
     SUMMARY OF THE INVENTION 
     In order to draw upon the benefits of the variable and higher capacity available with a linear compressor, the thermal storage system of the present invention stores thermal energy (i.e., a coolant) in a thermal storage unit with the compressor operating at a higher capacity during low load conditions. Under high demand situations, the stored coolant can be circulated in a heat exchanger for cooling the fresh food refrigerator compartment or be coupled in a circulation circuit to sub-cool the output of the condenser, lowering the condensing pressure of the refrigeration system and, thus, increasing the cooling capacity output of the compressor and offsetting the need to size the compressor and condenser for highest estimated demand based solely on condenser heat transfer limitations within a given ambient air temperature condition. Also, the stored coolant can simultaneously flow through both circulation circuits. In either mode, the operating efficiency of the refrigerator is improved by taking advantage of the capacity of the linear compressor in providing coolant which can be stored when the full capacity of the compressor is not needed for normal refrigerator operation. 
     The system of the present invention, therefore, provides a thermal storage unit coupled to a pump for circulating cooled heat transfer liquid from the thermal storage unit in at least one of two possible circuits. One circuit includes a heat exchanger coupled to the fresh food evaporator for either assisting in cooling the fresh food section of the refrigerator, for cooling the heat transfer liquid, or defrosting the fresh food evaporator. Another circuit includes a sub-cooler after the condenser for cooling the refrigerant output from the condenser to below ambient temperatures before entering the expansion device, thereby increasing the efficiency of the system. 
     In a preferred embodiment of the invention, a three-way valve is coupled from the output pump to couple the stored coolant selectively to one or the other or both of the coolant circuits. In another preferred embodiment of the invention, the thermal storage unit comprises a thermal storage tank for water or a water/alcohol mix or other secondary coolant typically used in a refrigeration system. Although the system is most efficient when used with a linear compressor having sufficient capacity to cool the liquid coolant for storage in the insulated thermal storage tank, it can also be used with a conventional rotary compressor to even out the demand on the compressor. 
     Thus, with the system of the present invention, the capacity available from a compressor can be employed during low demand situations to store thermal energy for use under high demand conditions to more efficiently operate the refrigeration system. 
     These and other features, objects and advantages of the present invention will become apparent to those skilled in the art upon reading the following description thereof together with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a side-by-side refrigerator freezer incorporating the thermal storage system of the present invention; 
         FIG. 2  is a schematic view of the components of the thermal storage system of the present invention; and 
         FIGS. 3A and 3B  are a table illustrating the various modes of operation of the refrigerator and the thermal storage system of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring initially to  FIG. 1 , there is shown a refrigerator freezer  10  embodying the present invention, which includes a side-by-side refrigerated cabinet  12  and a freezer cabinet  14 . Each of the cabinets  12  and  14  include side walls  11  and  13 , respectively, and a rear wall  15 . Refrigerator  10  also includes a closure door  16  for the refrigerator cabinet  12  which is hinged to cabinet  12  and a freezer door  18  hinged to the freezer cabinet  14 . Both doors  16  and  18  include suitable seals for providing an airtight thermally insulated sealed connection between the doors and respective cabinets. Although a side-by-side refrigerator/freezer is illustrated in  FIG. 1 , the present invention can be employed with any configuration of a refrigerator/freezer combination. 
     Refrigerator  10  is adapted to receive a variety of shelves and modules at different positions defined by, in the embodiment shown in  FIG. 1 , a plurality of horizontally spaced vertical rails  22  extending from the rear wall of the refrigerator and freezer compartments. In the embodiment shown, the supports are in the form of vertically extending rails with vertically spaced slots for receiving mounting tabs on shelf supports  23  and similar tabs on modules, such as modules  20 ,  24 ,  25 , and  26 , for attaching them in cantilevered fashion to the cabinets at selected incrementally located positions. The inside edges of doors  16  and  18  also include vertically spaced shelf supports, such as  27 , for positioning bins  30  and modules, such as  32 , in the doors. The shelves, modules, and bins and, thus, be located at a variety of selected locations within the cabinets  12  and  14  and doors  16  and  18  to allow the consumer to select different locations for convenience of use. 
     Some of the modules in refrigerator  10 , such as module  20 , may require operating utilities. Thus, module  20  may be a powered crisper or an instant thaw or chill module and may require utilities, such as cooled or heated fluids or electrical operating power. Other modules, such as module  26 , may likewise require operational utilities while modules, such as a passive crisper module  20 , would not. Door modules also, such as module  32 , may, for example, include a water dispenser, vacuum bag sealer or other accessory conveniently accessible either from the outside of door  16  or from within the door and likewise may receive operating utilities from conduits, such as disclosed in application Ser. No. 12/469,915, filed May 21, 2009, and entitled REFRIGERATOR MODULE MOUNTING SYSTEM, now U.S. Pat. No. 8,453,476; Ser. No. 12/469,968 filed May 21, 2009, and entitled MULTIPLE UTILITY RIBBON CABLE, now U.S. Pat. No. 8,505,328; and Ser. No. 12/493,524 filed Jun. 29, 2009 and entitled TUBULAR CONDUIT, now U.S. Pat. No. 8,281,608. The disclosures of these patent applications are incorporated herein by reference. 
     Contained within the insulated cabinets of the refrigerator are the usual freezer and fresh food evaporator, condenser, and the usual fluid couplings to a compressor for the operation of the refrigerator. Refrigerator  10  of this invention, however, includes the additional fluid circuits and thermal storage system as shown in the schematic diagram of  FIG. 2 , now described. 
     The schematic diagram of  FIG. 2  shows the locations of various major components of the refrigerator and thermal storage system in no particular relationship within the refrigerator cabinet, it being understood that, in practice, these elements can be located in any conventional or convenient location. For example, the condenser may conventionally be located in the back outside wall of the cabinet or in a compartment above cabinets  12 ,  14 . Thus, the schematic diagram of  FIG. 2  is illustrative only and does not necessarily limit the position of any of the components. 
     In  FIG. 2 , the heart of the refrigerator  10  is a linear compressor  40  which, due to its relatively flat elongated shape, can be located conveniently at nearly any location within the refrigerator, including in the space between the refrigerator inner liner and its outer shell. Frequently, the compressor is located near the top of the refrigerator near the condenser where heat can be evacuated upwardly and away from the refrigerator cabinet. The compressor  40  can be of the type described in U.S. patent application Ser. No. 10/553,944 filed Apr. 22, 2004, entitled SYSTEM FOR ADJUSTING RESONANT FREQUENCIES IN A LINEAR COMPRESSOR and published as Publication No. 2006/0110259 on May 25, 2006. The disclosure of this application and publication are incorporated herein by reference. Compressor  40  is coupled to a refrigeration circuit  60  including conduit  42  which couples the compressor to a condenser  44  and then to a two-way bypass valve  46 . The bypass valve  46  is selectively operated to either direct the refrigerant flow through a freezer compartment capillary  48  and into the freezer compartment evaporator  50  or via conduit  45  to the fresh food evaporator  49  through a thermostatic expansion valve  47  or other expansion device. When in a position to direct refrigerant to the freezer evaporator  50 , a check valve  52  is open to the suction line  54  leading to the input  41  of the compressor. With the valve  46  in the freezer compartment bypass position, the refrigerant flows through conduit  45  into a thermostatic expansion valve  47 , into the fresh food evaporator  49 , and then into the suction line  54  again leading to the input  41  of compressor  40 . Bypass valve  46  is selectively operated by a microprocessor-based control circuit to either allow the flow of refrigerant through the freezer evaporator  50  or, alternatively, through the fresh food evaporator  49  depending upon the thermal demand of the compartments  14 ,  12 , respectively. Though not illustrated thusly, suction line  54  typically is in thermal communication with freezer capillary  48  or fresh food expansion device  47  for operational efficiency. The components of the refrigeration system described thus far are typical components in a normal refrigeration system in which a microprocessor-based control circuit with suitable temperature sensors is employed and can be of a generally conventional design. 
     In addition to the coolant circuit for the freezer evaporator  50  and the fresh food evaporator  49  described, the system of the present invention adds parallel flow paths or first and second coolant circuits for circulating a chilled liquid from a thermal storage tank  70 . Tank  70  is a thermally insulated tank and can be placed in the fresh food compartment or otherwise located in the machine compartment section of a given refrigerator/freezer configuration. Tank  70  typically is blow molded of a suitable polymeric material, such as PVC or polyethylene, and insulated by a jacket. It could be a Dewar flask or thermos vacuum bottle type tank using metal plated polymers as chrome plates onto ABS and other polymers very well to provide a highly reflective surface. The size of tank  70  depends on the intended application. If the stored thermal mass is strictly for a single refrigerator, then it may have a capacity of 1 to 4 liters for holding approximately 0.75 to 3 kgs of, for example, a water/alcohol solution. If a secondary circuit for supplemental devices, such as counter top devices or the like, are coupled to refrigerator  10 , tank  70  could be two to three times larger. The tank includes an output connection  72  and two input connections  74  and  76  for circulating stored liquid coolant through two separate circuits either to chill the coolant or to transfer heat from the refrigerator components to the chilled coolant. 
     Output connection  72  is coupled by conduit  71  to the input  81  of liquid pump  80  having an output  82  coupled to a three-way valve  90 . Valve  90  has three positions which can direct fluid from output  82  of pump  80  to a first conduit  92 , a second conduit  94 , or to both conduits simultaneously depending upon the position of the three-way valve  90 . In one position, only conduit  92  is coupled to the output of pump  80  and couples the chilled fluid from tank  70  to a first circuit including a secondary heat exchanger  100  in thermal communication with fresh food evaporator  49 . The secondary heat exchanger is coupled by a return conduit  93  to input  76  of thermal storage tank  70  to complete the first circulation circuit. 
     A second circulation circuit includes conduit  94  coupled to valve  90  and coupled to a sub-cooler  96  surrounding the conduit  60  between the condenser  44  and bypass valve  46  to sub-cool the typically warm refrigerant liquid from the condenser before it enters an expansion device. A return conduit  97  from sub-cooler  96  leads back to the input  74  of thermal storage tank  70 . Finally, in a third position of valve  90 , the chilled coolant in thermal storage tank  70  is simultaneously circulated through both the first circulation circuit including the secondary heat exchanger  100  and the second circulation circuit including the sub-cooler  96 . 
     The coolant employed for the thermal storage tank  70  and circulated by pump  80  can be one of a number of conventional coolants employed in the refrigeration industry, such as water, a water/alcohol mixture, brine, or a Dynalene® heat transfer fluid. The thermal storage tank, once filled through a suitable opening which is subsequently sealed after the circulation circuits through the sub-cooler  96  and secondary heat exchanger  100  have been purged of air, provides sealed liquid circuits or loops for the chilled thermal medium being pumped by pump  80 . 
     The coolant in the thermal storage tank is chilled by the secondary heat exchanger  100  when the compressor  40  is in operation to provide cooling to the fresh food evaporator  49  under conditions where excess capacity from the compressor is available. Thus, when valve  46  is moved to a position to supply refrigerant through line  45  and throttle valve  47  to the fresh food evaporator  49  (unless under a high load condition for the refrigeration cabinet  12 ), the excess cooling available is employed by heat exchanger  100  to chill the thermal media circulated by pump  80  through the first circulation circuit, including conduit  71 , pump inlet  81 , valve  90 , conduit  92 , heat exchanger  100 , and conduit  93 , back to tank  70  to chill the liquid coolant. The overall operation of the system during different modes of operation is best seen by the chart of  FIGS. 3A and 3B , which shows the status of the valves, the compressor, and the thermal storage pump during different scenarios of operation. 
     In line  200 , the refrigeration mode is in the freezer operation under low or normal load conditions. In this mode of operation, compressor  40  is on and can be in low capacity operation if a variable capacity compressor, such as a linear compressor, is employed. The potential temperature of the liquid in the thermal storage tank is at standby and may be, if located within the fresh food compartment  12 , somewhat cooled. The bypass valve  46  is off to allow the refrigerant to pass through the freezer evaporator  50  while the three-way valve  90  is turned off to close off both first and second circulation circuits. Check valve  52  is opened while the throttle valve  47  is on standby. In this mode, the thermal storage system is in the standby mode with no circulation of coolant through the tank  70 . 
     In the second mode of operation indicated at line  202 , the fresh food compartment  12  is in operation with the compressor on medium to high capacity and the thermal storage tank  70  in either a low or medium cooling state. The bypass valve  46  is set to circulate refrigerant through line  45  through valve  47  to provide coolant to the fresh food evaporator  49 . At the same time, pump  80  is activated with valve  90  turned on to circulate the coolant through the first circuit, including line  71 , pump  80 , line  82 , valve  90 , line  92  through secondary heat exchanger  100  and returning to tank  70  through line  93  and input  76 . In this position, check valve  52  is closed, while the throttle valve  47  is open. During this interval of operation, the coolant is chilled by thermal communication between heat exchanger  100  and evaporator  49 . Thus, the thermal storage tank  70  banks thermal capacity during the evaporator  49  operation for use at a later time to cool fresh food. If compressor  40  is off, then the secondary heat exchanger  100  can provide cooling to the fresh food compartment  12  or potentially defrost the fresh food evaporator  49 . 
     In line  204 , the mode of operation is the freezer in operation under high load conditions. 
     Compressor  40  is operating at its maximum capacity, while the coolant in the thermal storage tank can be anywhere from a low to a high cooling potential level. In this condition, the bypass valve  46  is set to direct refrigerant to the freezer evaporator  50  and the thermal storage pump is on with the valve  90  open to the sub-cooler  96  to allow the coolant from tank  70  to be pumped through line  94  through the sub-cooler  96  and return via line  97  to the storage tank  70 . In this position, the throttle valve  47  is in a standby mode and the chilled liquid in thermal storage tank  70  is employed for sub-cooling the compressor discharge, which lowers the condensing pressure and increases the availability of cooling for the freezer evaporator capacity. During this mode, the stored thermal energy (in the form of cooling ability) and the thermal storage tank  70  is used to reduce the temperature of the refrigerant exiting the condenser, thereby improving the efficiency of the system and increasing system capacity beyond that obtainable by solely rejecting heat to the ambient air via the condenser. 
     In the next mode of operation shown on line  206 , fresh food evaporator  49  is being operated with the bypass valve  46  set to the fresh food compartment and the linear compressor is in a medium to high operational mode and a potential state of thermal state of thermal storage tank can be anywhere from low to high in terms of capacity to provide additional cooling. The storage pump  80  is turned on and the three-way valve setting  90  is open to circulate the coolant through the secondary heat exchanger  100 . In this condition where the fresh food evaporator is operative in the refrigerant circuit, the throttle valve  47  is open. In this mode, the system banks whatever thermal capacity during fresh food evaporator circuit operation is available and, in the event the compressor  40  is turned off, the circulation of coolant from tank  70  through secondary heat exchanger  100  provides cooling or potential defrosting to the fresh food evaporator and to the fresh food storage compartment  12 . 
     In the next mode of operation represented by line  208  ( FIG. 3B ), again the fresh food evaporator is in an operational mode, however, under low load conditions. The compressor  40  is off in this position, and the thermal storage media is in a medium to high potential cooling state. The bypass valve  46  is set to the fresh food compartment and the circulation pump  80  is turned on with the valve  90  open to the first circulation circuit as in the prior mode of operation. The fresh food throttle valve  47  is in standby state inasmuch as the compressor is now off. In this mode, as indicated in the last column of the chart, the bank of thermal capacity in terms of cooling ability is employed for fresh food cooling of compartment  12  or defrosting of the fresh food evaporator  49 . 
     In the next mode of operation, the freezer is being operated, as shown by line  210 , with the compressor  40  on and in a low capacity mode if it is a variable capacity compressor, such as the linear compressor of the preferred embodiment of the invention. In this condition, the freezer load is low or normal and the bypass valve  46  is set to direct refrigerant through the freezer evaporator  50 . The three-way valve  90  is closed, and pump  80  is off. Check valve  52  is open to allow the refrigerant to circulate back through the compressor through suction line  54  and the throttle valve  47  is in standby mode. In this mode of operation, thermal storage tank  70  is inactive, however, if it is positioned within the fresh food compartment, it will potentially provide some cooling to the fresh food compartment while in a standby mode depending on the temperature of the stored thermal mass. 
     Next, as indicated by line  212 , again, the compressor  40  is on in a low capacity mode of operation and the bypass valve  46  is set to the freezer compartment. In this mode of operation, the freezer and fresh food compartments are in low or normal system load conditions. The thermal storage system pump  80  is turned on, while the three-way valve  90  is open to the first circulation circuit, including secondary heat exchanger  100 . Check valve  52  is open, while the throttle valve  47  is in a standby mode. In this mode also, the available coolant from the liquid coolant in storage tank  70  is used to cool the fresh food compartment while the refrigerant in a normal circulation circuit for refrigerant is being employed in the freezer compartment through the freezer evaporator  50 . 
     Finally, with valve  90  open to both circulation circuits, the chilled fluid from tank  70  is circulated through both the secondary heat exchanger  100  to cool the fresh food compartment  12  and sub-cool the compressor output through sub-cooler  96 . This operation is represented by line  214  in the table of  FIG. 3B . 
     Thus, in the various modes of operation, the excess thermal capacity of the compressor is employed for storing thermal energy in the form of cooling the liquid coolant in thermal storage tank  70 , which can be subsequently used in either the first circulation circuit for either cooling to the liquid cooling medium when the refrigerant from compressor  40  is being applied to the fresh food evaporator  49  or for providing cooling to the fresh food compartment when the bypass valve  46  is in the freezer position. Alternately, when there is no need for coolant in the liquid storage tank to be additionally cooled, it can be employed for sub-cooling the output of condenser  44 , thereby increasing the efficiency of the system in operation when either the freezer compartment or fresh food compartment or external supported thermal load (as disclosed in application Ser. No. 12/469,915, filed May 21, 2009, and entitled REFRIGERATOR MODULE MOUNTING SYSTEM, now U.S. Pat. No. 8,453,476; Ser. No. 12/469,968 filed May 21, 2009, and entitled MULTIPLE UTILITY RIBBON CABLE, now U.S. Pat. No. 8,505,328; and Ser. No. 12/493,524 filed Jun. 29, 2009 and entitled TUBULAR CONDUIT, now U.S. Pat. No. 8,281,608) is under high load conditions. 
     The operational states of the valves are controlled by an electrical control system which is programmed according to the settings set forth in the table of  FIGS. 3A and 3B  in a conventional manner to achieve the desired switching of the valve positions and the operation of pump  80  in coordination with the control circuit for compressor  40 . Thus, with the system of the present invention, the capacity available from the compressor and, particularly, as in the preferred embodiment, a linear compressor with greater capacity and flexibility is employed, can be used to more efficiently operate the refrigeration system and even out the demand on both the compressor and other refrigeration components. 
     It will become apparent to those skilled in the art that various modifications to the preferred embodiments of the invention as described herein can be made without departing from the spirit or scope of the invention as defined by the appended claims.