Refrigeration cycle system

Abstract

Power consumption is reduced in a refrigeration cycle system including a cascade heat exchanger that causes heat exchange between a CO2 refrigerant and a refrigerant other than CO2, the refrigeration cycle system implementing a first refrigeration cycle using the CO2 refrigerant and a second refrigeration cycle using the refrigerant other than CO2. A controller controls a first compressor and a second compressor such that an intermediate temperature Tm between an evaporation temperature of a first refrigerant and a condensation temperature of a second refrigerant in a cascade heat exchanger satisfies T2+(T1−T2)×0.1≤TV≤T2+(T1−T2)×0.4, where T1° C. represents a pressure equivalent saturation temperature of a refrigerant discharged from the first compressor, and T2° C. represents a pressure equivalent saturation temperature of a refrigerant sucked into the second compressor.

1 . A refrigeration cycle system comprising:
 a first refrigerant circuit including a first compressor that circulates a first refrigerant at a discharge refrigerant pressure in a range of 0.5 MPa or more and 4 MPa or less and a cascade heat exchanger that cools a second refrigerant that is a CO 2  refrigerant by the first refrigerant, the first refrigeration circuit implementing a first vapor compression refrigeration cycle using the first refrigerant;   a second refrigerant circuit including a second compressor that circulates the second refrigerant at a discharge refrigerant pressure in a range of 5 MPa or more and 14 MPa or less, the second refrigerant circuit implementing a second vapor compression refrigeration cycle using the second refrigerant; and   a controller that controls the first compressor and the second compressor, wherein   the controller controls the first compressor and the second compressor such that an intermediate temperature TV between an evaporation temperature of the first refrigerant and a condensation temperature of the second refrigerant in the cascade heat exchanger satisfies
     T 2+( T 1− T 2)×0.1≤ TV≤T 2+( T 1− T 2)×0.4
 
   in which a pressure equivalent saturation temperature in ° C. of a refrigerant discharged from the first compressor is T1 and a pressure equivalent saturation temperature in ° C. of a refrigerant sucked into the second compressor is T2.   
     
     
         2 . The refrigeration cycle system according to  claim 1 , wherein the first refrigerant includes R32, R454C, propane, R1234yf, R1234ze, or ammonia, or a refrigerant including any of R32, R454C, propane, R1234yf, R1234ze, or ammonia. 
     
     
         3 . The refrigeration cycle system according to  claim 1 , wherein the second refrigerant circuit condenses the second refrigerant in the cascade heat exchanger. 
     
     
         4 . The refrigeration cycle system according to  claim 3 , wherein the second refrigerant circuit includes an indoor heat exchanger that causes heat exchange between indoor air and the second refrigerant. 
     
     
         5 . The refrigeration cycle system according to  claim 4 , wherein the first refrigerant circuit includes an outdoor heat exchanger that causes heat exchange between outside air and the first refrigerant. 
     
     
         6 . The refrigeration cycle system according to  claim 2 , wherein the second refrigerant circuit condenses the second refrigerant in the cascade heat exchanger. 
     
     
         7 . The refrigeration cycle system according to  claim 6 , wherein the second refrigerant circuit includes an indoor heat exchanger that causes heat exchange between indoor air and the second refrigerant. 
     
     
         8 . The refrigeration cycle system according to  claim 7 , wherein the first refrigerant circuit includes an outdoor heat exchanger that causes heat exchange between outside air and the first refrigerant. 
     
     
         9 . The refrigeration cycle system according to  claim 1 , wherein a total power consumption of the refrigeration cycle system is 9.5 kW or less. 
     
     
         10 . The refrigeration cycle system according to  claim 1 , wherein a total power consumption of the refrigeration cycle system is 9.4 kW or less. 
     
     
         11 . The refrigeration cycle system according to  claim 1 , further comprising:
 a high-pressure pressure sensor on a discharge side of the first compressor, the high-pressure pressure sensor detecting the pressure equivalent saturation temperature T1 of refrigerant discharged from the first compressor; and   a low-pressure pressure sensor on a suction side of the second compressor, the low-pressure pressure sensor detecting the pressure equivalent saturation temperature T2 of refrigerant sucked into the second compressor.