Cascade refrigeration cycle system and cascade refrigeration cycle system control method

Abstract

A cascade refrigeration cycle system includes: a high-order side refrigerant circuit through which a high-order side refrigerant circulates; a low-order side refrigerant circuit through which a low-order side refrigerant circulates; a high-order side heat accumulation circuit including a heat accumulation heat exchanger provided in parallel with a cascade heat exchanger through which the high-order side refrigerant circulates; a low-order side heat accumulation circuit including the heat accumulation heat exchanger through which the low-order side refrigerant circulates; a refrigerant temperature detecting unit configured to measure or calculate a saturation temperature of the low-order side refrigerant discharged from a low-order side compressor; a heat accumulation temperature sensor configured to measure the temperature of a heat accumulation material; and a control unit. When performing a heating operation, the control unit acquires information on the saturation temperature and information on the temperature of the heat accumulation material and controls the low-order side compressor.

1 . A cascade refrigeration cycle system comprising:
 a high-order side refrigerant circuit configured such that a high-order side compressor, a high-order side heat exchanger, a first high-order side pressure reduction mechanism, and a cascade heat exchanger are sequentially connected via refrigerant pipes to circulate a high-order side refrigerant through the high-order side refrigerant circuit;   a low-order side refrigerant circuit configured such that a low-order side compressor, the cascade heat exchanger, a first low-order side pressure reduction mechanism, and a low-order side heat exchanger are sequentially connected via refrigerant pipes to circulate a low-order side refrigerant through the low-order side refrigerant circuit;   a high-order side heat accumulation circuit configured such that the high-order side compressor, the high-order side heat exchanger, a second high-order side pressure reduction mechanism, and a heat accumulation heat exchanger provided in parallel with the cascade heat exchanger are sequentially connected via refrigerant pipes to circulate the high-order side refrigerant through the high-order side heat accumulation circuit;   a low-order side heat accumulation circuit configured such that the low-order side compressor, the heat accumulation heat exchanger, a second low-order side pressure reduction mechanism, and the low-order side heat exchanger are sequentially connected via refrigerant pipes to circulate the low-order side refrigerant through the low-order side heat accumulation circuit;   a refrigerant temperature detecting unit configured to measure or calculate a saturation temperature of the low-order side refrigerant discharged from the low-order side compressor;   a heat accumulation temperature sensor configured to measure a temperature of a heat accumulation material provided in the heat accumulation heat exchanger; and   a control unit configured to control respective openings of the high-order side compressor, the low-order side compressor, the first high-order side pressure reduction mechanism, the second high-order side pressure reduction mechanism, the first low-order side pressure reduction mechanism, and the second low-order side pressure reduction mechanism, wherein:   the high-order side refrigerant and the low-order side refrigerant perform heat-exchange in the cascade heat exchanger or the heat accumulation heat exchanger; and   at a time of performing a heating operation, the control unit acquires information on the saturation temperature and information on the temperature of the heat accumulation material and controls the low-order side compressor such that a temperature difference between the saturation temperature and the temperature of the heat accumulation material becomes a first predetermined value.   
     
     
         2 . The cascade refrigeration cycle system according to  claim 1 , further comprising:
 an indoor unit provided in an indoor space and including the high-order side heat exchanger and a room temperature sensor configured to measure a room temperature of the indoor space, wherein, in a case where the room temperature reaches a preset temperature set in the indoor unit, the control unit controls the low-order side compressor such that the temperature difference between the saturation temperature and the temperature of the heat accumulation material becomes the a second predetermined value.   
     
     
         3 . The cascade refrigeration cycle system according to  claim 2 , wherein the control unit sets the second predetermined value to be equal to or more than the first predetermined value. 
     
     
         4 . The cascade refrigeration cycle system according to  claim 3 , wherein:
 the control unit acquires information on the temperature of the heat accumulation material; and   in a case where the temperature of the heat accumulation material reaches a predetermined temperature, the control unit stops heat accumulation in the heat accumulation heat exchanger.   
     
     
         5 . The cascade refrigeration cycle system according to  claim 1 , wherein, during the heating operation using the first predetermined value or the second predetermined value, the control unit performs a control to open the first high-order side pressure reduction mechanism, the first low-order side pressure reduction mechanism, and the second low-order side pressure reduction mechanism and to close the second high-order side pressure reduction mechanism. 
     
     
         6 . The cascade refrigeration cycle system according to  claim 1 , wherein the control unit performs a control to close the first low-order side pressure reduction mechanism and the first high-order side pressure reduction mechanism at a time of performing a defrosting operation on the low-order side heat exchanger. 
     
     
         7 . A control method for controlling a cascade refrigeration cycle system including
 a high-order side refrigerant circuit configured such that a high-order side compressor, a high-order side heat exchanger, a first high-order side pressure reduction mechanism, and a cascade heat exchanger are sequentially connected via refrigerant pipes to circulate a high-order side refrigerant through the high-order side refrigerant circuit,   a low-order side refrigerant circuit configured such that a low-order side compressor, the cascade heat exchanger, a first low-order side pressure reduction mechanism, and a low-order side heat exchanger are sequentially connected via refrigerant pipes to circulate a low-order side refrigerant through the low-order side refrigerant circuit,   a high-order side heat accumulation circuit configured such that the high-order side compressor, the high-order side heat exchanger, a second high-order side pressure reduction mechanism, and a heat accumulation heat exchanger provided in parallel with the cascade heat exchanger are sequentially connected via refrigerant pipes to circulate the high-order side refrigerant through the high-order side heat accumulation circuit,   a low-order side heat accumulation circuit configured such that the low-order side compressor, the heat accumulation heat exchanger, a second low-order side pressure reduction mechanism, and the low-order side heat exchanger are sequentially connected via refrigerant pipes to circulate the low-order side refrigerant through the low-order side heat accumulation circuit;   a refrigerant temperature detecting unit configured to measure or calculate a saturation temperature of the low-order side refrigerant discharged from the low-order side compressor,   a heat accumulation temperature sensor configured to measure a temperature of a heat accumulation material provided in the heat accumulation heat exchanger, and   a control unit configured to control respective openings of the high-order side compressor, the low-order side compressor, the first high-order side pressure reduction mechanism, the second high-order side pressure reduction mechanism, the first low-order side pressure reduction mechanism, and the second low-order side pressure reduction mechanism,   the control method comprising:   the control unit acquiring information on the saturation temperature and information on the temperature of the heat accumulation material at a time of performing a heating operation; and   controlling the low-order side compressor such that a temperature difference between the saturation temperature and the temperature of the heat accumulation material becomes a first predetermined value.   
     
     
         8 . The control method according to  claim 7 , further comprising:
 determining whether or not a room temperature of an indoor space reaches a preset temperature set in an indoor unit which is provided in the indoor space and which includes the high-order side heat exchanger and a room temperature sensor configured to measure the room temperature of the indoor space;   acquiring the information on the saturation temperature and the information on the temperature of the heat accumulation material in a case where the room temperature is determined to reach the preset temperature; and   controlling the low-order side compressor such that the temperature difference between the saturation temperature and the temperature of the heat accumulation material becomes a second predetermined value.   
     
     
         9 . The control method according to  claim 8 , wherein the control unit sets the second predetermined value to be equal to or more than the first predetermined value. 
     
     
         10 . The control method according to  claim 8 , further comprising:
 acquiring the information on the temperature of the heat accumulation material;   determining whether or not the temperature of the heat accumulation material reaches a predetermined temperature; and   in a case where the temperature of the heat accumulation material is determined to reach the predetermined temperature, stopping heat accumulation in the heat accumulation heat exchanger.   
     
     
         11 . The control method according to  claim 7 , further comprising:
 opening the first high-order side pressure reduction mechanism, the first low-order side pressure reduction mechanism, and the second low-order side pressure reduction mechanism during the heating operation using the first predetermined value or a second predetermined value; and   closing the second high-order side pressure reduction mechanism.   
     
     
         12 . The control method according to  claim 7 , further comprising:
 closing the first low-order side pressure reduction mechanism and the first high-order side pressure reduction mechanism at a time of performing a defrosting operation on the low-order side heat exchanger.   
     
     
         13 . The cascade refrigeration cycle system according to  claim 2 , wherein, during the heating operation using the first predetermined value or the second predetermined value, the control unit performs a control to open the first high-order side pressure reduction mechanism, the first low-order side pressure reduction mechanism, and the second low-order side pressure reduction mechanism and to close the second high-order side pressure reduction mechanism. 
     
     
         14 . The cascade refrigeration cycle system according to  claim 3 , wherein, during the heating operation using the first predetermined value or the second predetermined value, the control unit performs a control to open the first high-order side pressure reduction mechanism, the first low-order side pressure reduction mechanism, and the second low-order side pressure reduction mechanism and to close the second high-order side pressure reduction mechanism. 
     
     
         15 . The cascade refrigeration cycle system according to  claim 4 , wherein, during the heating operation using the first predetermined value or the second predetermined value, the control unit performs a control to open the first high-order side pressure reduction mechanism, the first low-order side pressure reduction mechanism, and the second low-order side pressure reduction mechanism and to close the second high-order side pressure reduction mechanism. 
     
     
         16 . The control method according to  claim 8 , further comprising:
 opening the first high-order side pressure reduction mechanism, the first low-order side pressure reduction mechanism, and the second low-order side pressure reduction mechanism during the heating operation using the first predetermined value or a second predetermined value; and   closing the second high-order side pressure reduction mechanism.   
     
     
         17 . The control method according to  claim 9 , further comprising:
 opening the first high-order side pressure reduction mechanism, the first low-order side pressure reduction mechanism, and the second low-order side pressure reduction mechanism during the heating operation using the first predetermined value or a second predetermined value; and   closing the second high-order side pressure reduction mechanism.   
     
     
         18 . The control method according to  claim 10 , further comprising:
 opening the first high-order side pressure reduction mechanism, the first low-order side pressure reduction mechanism, and the second low-order side pressure reduction mechanism during the heating operation using the first predetermined value or a second predetermined value; and   closing the second high-order side pressure reduction mechanism.