Refrigeration System

Abstract

A refrigeration system ( 10 ) includes: a refrigerant circuit ( 15 ) including a low-pressure stage compressor ( 21 ) variable in displacement and a high-pressure stage compressor ( 31 ) variable in displacement and operating in a two-stage compression refrigeration cycle; and a controller ( 100 ) for controlling the operation of the refrigeration system ( 10 ). The controller ( 100 ) includes a first control section ( 101 ) and a second control section ( 102 ). The first control section ( 101 ) controls the operating capacity of the low-pressure stage compressor ( 21 ) to adapt to the load of the refrigeration capacity. The second control section ( 102 ) controls the operating capacity of the high-pressure stage compressor ( 31 ) so that the ratio between a first pressure ratio, which is the ratio of the discharge pressure of the low-pressure stage compressor ( 21 ) to the suction pressure thereof, and a second pressure ratio, which is the ratio of the discharge pressure of the high-pressure stage compressor ( 31 ) to the suction pressure thereof, is 1:1.

1 . A refrigeration system that includes a refrigerant circuit ( 15 ) including a first compression mechanism ( 21 ,  31 ) variable in displacement and a second compression mechanism ( 31 ,  21 ) variable in displacement and operates in a two-stage compression refrigeration cycle, the refrigeration system further including:
 a first control means ( 101 ) for increasing and decreasing the operating capacity of the first compression mechanism ( 21 ,  31 ) to adapt to the load of the refrigeration capacity; and   a second control means ( 102 ) for increasing and decreasing the operating capacity of the second compression mechanism ( 31 ,  21 ) so that the intermediate pressure in the two-stage compression refrigeration cycle has a predetermined value.   
   
   
       2 . The refrigeration system of  claim 1 , wherein the second control means ( 102 ) controls the operating capacity of the second compression mechanism ( 31 ,  21 ) so that the ratio between a first pressure ratio, which is the ratio of the discharge pressure of the first compression mechanism ( 21 ,  31 ) to the suction pressure thereof, and a second pressure ratio, which is the ratio of the discharge pressure of the second compression mechanism ( 31 ,  21 ) to the suction pressure thereof, is 1:1. 
   
   
       3 . The refrigeration system of  claim 1 , further including a third control means ( 103 ) that, at startup, controls the operating capacity of the second compression mechanism ( 31 ,  21 ) instead of the second control means ( 102 ) so that the second compression mechanism ( 31 ,  21 ) has a predetermined target operating capacity derived based on the operating capacity of the first compression mechanism ( 21 ,  31 ). 
   
   
       4 . The refrigeration system of  claim 1 ,
 wherein during a heating operation, the first compression mechanism ( 21 ,  31 ) comprises a low-pressure stage compression mechanism ( 21 ) and the second compression mechanism ( 31 ,  21 ) comprises a high-pressure stage compression mechanism ( 31 ), and   wherein during the heating operation, the first control means ( 101 ) controls the operating capacity of the low-pressure stage compression mechanism ( 21 ) so that the discharge pressure of the high-pressure stage compression mechanism ( 31 ) has a predetermined target value while the second control means ( 102 ) controls the operating capacity of the high-pressure stage compression mechanism ( 31 ) so that the intermediate pressure has a predetermined value.   
   
   
       5 . The refrigeration system of  claim 1 ,
 wherein during a cooling operation, the first compression mechanism ( 21 ,  31 ) comprises a high-pressure stage compression mechanism and the second compression mechanism ( 31 ,  21 ) comprises a low-pressure stage compression mechanism, and   wherein during the cooling operation, the first control means ( 101 ) controls the operating capacity of the high-pressure stage compression mechanism ( 31 ) so that the discharge pressure of the low-pressure stage compression mechanism ( 21 ) has a predetermined target value while the second control means ( 102 ) controls the operating capacity of the low-pressure stage compression mechanism ( 21 ) so that the intermediate pressure has a predetermined value.   
   
   
       6 . The refrigeration system of  claim 1 , wherein the first compression mechanism ( 21 ,  31 ) and the second compression mechanism ( 31 ,  21 ) are inverter-controlled.