Refrigerator with a phase change material as a thermal store

Abstract

A refrigerator having a thermal store comprising a phase change material is disclosed. The refrigerator has a cooling chamber for containing an object to be cooled, and a vapor compression refrigeration system including a first evaporator for cooling the cooling chamber and a second evaporator for cooling the phase change material. A valve is provided to control the flow of refrigerant to the first and second evaporators depending on the cooling load on the refrigerator. When the refrigerator is subject to a relatively low cooling load, refrigerant flows to the second evaporator to cool the phase change material and, when the refrigerator is subject to a relatively high cooling load, refrigerant flows to the first evaporator such that increased cooling is provided to the cooling chamber by the first evaporator and the phase change material.

1 . A refrigerator comprising:
 a cooling chamber configured and arranged to contain an object to be cooled;   a thermal store including a phase change material;   a vapor compression refrigeration system including a first evaporator for cooling the cooling chamber and a second evaporator for cooling the phase change material; and   a valve and a valve position controller circuit configured and arranged to control flow of refrigerant to the first and second evaporators depending on the cooling load on the refrigerator, by
 when the refrigerator is subject to a relatively low cooling load, controlling a position of the valve with the valve position controller circuit to flow refrigerant to the second evaporator to cool the phase change material and, 
 when the refrigerator is subject to a relatively high cooling load, controlling the position of the valve with the valve position controller circuit to flow refrigerant to the first evaporator such that increased cooling is provided to the cooling chamber by the first evaporator and the phase change material, relative to cooling provided when the refrigerator is subject to the relatively low cooling load. 
   
     
     
         2 . The refrigerator of  claim 1 , wherein the valve and valve position controller circuit are configured and arranged to flow refrigerant to both the first and second evaporators when the refrigerator is subject to the relatively low cooling load. 
     
     
         3 . The refrigerator of  claim 1 , wherein the valve and valve position controller circuit are configured and arranged to flow refrigerant substantially only to the first evaporator when the refrigerator is subject to a relatively high cooling load. 
     
     
         4 . The refrigerator of  claim 1 , wherein the phase change material exhibits at least two phases, and the valve position controller circuit is configured and arranged to control the position of the valve based on relative proportions of the phase change material in each of the at least two phases. 
     
     
         5 . The refrigerator of  claim 1 , wherein the valve is a bistable valve. 
     
     
         6 . The refrigerator of  claim 1 , further including a temperature sensor configured and arranged to determine the temperature of the cooling chamber, wherein the controller circuit is configured and arranged with the temperature sensor to control the position of the valve based on temperature indicated by the temperature sensor. 
     
     
         7 . The refrigerator of  claim 1 , further including sensor configured and arranged to determine the relative proportions of the phases of the phase change material, and wherein the valve position controller circuit is configured and arranged to control the valve position based on the relative proportions of the phases of the phase change material indicated via the sensor. 
     
     
         8 . The refrigerator of  claim 1 , wherein the vapor compression refrigeration system includes a compressor, and wherein the valve position controller circuit is configured and arranged to control the amount of cooling provided to the cooling chamber by controlling the compressor. 
     
     
         9 . The refrigerator of  claim 1 , wherein the refrigerator further comprises a fan configured and arranged to circulate air from the cooling chamber to the thermal store and the first evaporator for cooling, and the valve position controller circuit is configured and arranged with the fan to control the amount of cooling provided to the cooling chamber by controlling the operation or speed of the fan. 
     
     
         10 . The refrigerator of  claim 1 , wherein the thermal store includes two opposing cooling surfaces configured and arranged to flow air over either side of the thermal store to pass across both cooling surfaces. 
     
     
         11 . The refrigerator of  claim 10 , wherein the first evaporator is positioned downstream of the thermal store. 
     
     
         12 . The refrigerator of  claim 1 , wherein the second evaporator is embedded within the thermal store. 
     
     
         13 . The refrigerator of  claim 1 , wherein the valve and valve position controller circuit are configured and arranged to flow the refrigerant substantially only to the first evaporator in response to a temperature within the refrigerator exceeding a desired temperature and, in response to the temperature dropping back to the desired temperature, freezing the phase change material by flowing refrigerant to the second evaporator. 
     
     
         14 . A method for use with a refrigerator having a cooling chamber configured and arranged to contain an object to be cooled, a thermal store including a phase change material, a vapor compression refrigeration system including a first evaporator for cooling the cooling chamber and a second evaporator for cooling the phase change material, the method comprising:
 when the refrigerator is subject to a relatively low cooling load, cooling the phase change material by flowing refrigerant to the second evaporator, and   when the refrigerator is subject to a relatively high cooling load, providing increased cooling to the cooling chamber from the first evaporator and the phase change material by flowing refrigerant to the first evaporator.   
     
     
         15 . The method of  claim 14 , wherein flowing refrigerant to the second evaporator and flowing refrigerant to the first evaporator include using a valve and a valve position controller circuit to control flow of refrigerant to the first and second evaporators based on the cooling load. 
     
     
         16 . The method of  claim 14 , further including flowing refrigerant to the first evaporator when the refrigerator is subject to the relatively low cooling load. 
     
     
         17 . The method of  claim 14 , wherein providing increased cooling to the cooling chamber from the first evaporator includes flowing refrigerant substantially only to the first evaporator. 
     
     
         18 . The method of  claim 14 , wherein flowing refrigerant to the second evaporator includes flowing the refrigerant based on relative proportions of the phase change material in respective phases. 
     
     
         19 . The method of  claim 14 , wherein providing the increased cooling to the cooling chamber includes flowing air over the thermal store and the first evaporator. 
     
     
         20 . The method of  claim 14 ,
 wherein providing the increased cooling includes flowing the refrigerant substantially only to the first evaporator in response to a temperature within the refrigerator exceeding a desired temperature,   further including, in response to the temperature dropping back to the desired temperature, freezing the phase change material by flowing refrigerant to the second evaporator.