Refrigeration cycle apparatus

Abstract

A refrigeration cycle apparatus 100 is provided with a refrigerant circuit 106, an injection flow passage 111, and a high-pressure supply passage 130. The refrigerant circuit 106 includes a low-pressure stage compressor 105, a high-pressure stage compressor 101, a heat radiator 102, an expander 103, a gas-liquid separator 108, and an evaporator 104. The expander 103 and the low-pressure stage compressor 105 are coupled by a power-recovery shaft 107. The refrigeration cycle apparatus 100 is further provided with a flow passage-switching mechanism that selectively connects one of the evaporator 104 and the high-pressure supply passage 130 to the low-pressure stage compressor 105. The flow passage-switching mechanism, for example, is constituted by an on-off valve 131 and a check valve 132.

1 . A refrigeration cycle apparatus comprising:
 a main refrigerant circuit having
 a low-pressure stage compressor that compresses a refrigerant, 
 a high-pressure stage compressor that further compresses the refrigerant that has been compressed in the low-pressure stage compressor, 
 a heat radiator that cools the refrigerant that has been compressed in the high-pressure stage compressor, 
 an expander that recovers power from the refrigerant that has been cooled in the heat radiator while expanding the refrigerant, the expander being coupled to the low-pressure stage compressor by a shaft so that the recovered power is transferred to the low-pressure stage compressor, 
 a gas-liquid separator that separates the refrigerant that has been expanded in the expander into a gas refrigerant and a liquid refrigerant, and 
 an evaporator that evaporates the liquid refrigerant that has been separated in the gas-liquid separator; 
   an injection flow passage that introduces the gas refrigerant that has been separated in the gas-liquid separator into a portion of the main refrigerant circuit from a discharge port of the low-pressure stage compressor to a suction port of the high-pressure stage compressor;   a high-pressure supply passage that communicates a portion of the main refrigerant circuit from a discharge port of the high-pressure stage compressor to a suction port of the expander and a portion of the main refrigerant circuit from an outlet of the evaporator to a suction port of the low-pressure stage compressor;   a flow passage-switching mechanism capable of selectively connecting one selected from the evaporator and the high-pressure supply passage to the low-pressure stage compressor so that the refrigerant is introduced from the evaporator or the high-pressure supply passage to the low-pressure stage compressor; and   a controller that controls the flow passage-switching mechanism before activation of the expander and the low-pressure stage compressor so that the refrigerant is introduced from the high-pressure supply passage to the low-pressure stage compressor, while controlling the flow passage-switching mechanism after the activation of the expander and the low-pressure stage compressor so that the refrigerant is introduced from the evaporator to the low-pressure stage compressor, wherein   a discharge pressure of the high-pressure stage compressor is applied to the suction port of the low-pressure stage compressor and the suction port of the expander while a suction pressure of the high-pressure stage compressor is applied to the discharge port of the low-pressure stage compressor and a discharge port of the expander before activation of the expander and the low-pressure stage compressor.   
     
     
         2 . The refrigeration cycle apparatus according to  claim 1 , wherein
 the high-pressure supply passage has an upstream end connected to a portion of the main refrigerant circuit from the discharge port of the high-pressure stage compressor to an inlet of the heat radiator.   
     
     
         3 . The refrigeration cycle apparatus according to  claim 1 , wherein
 the high-pressure supply passage has a downstream end connected to a portion of the main refrigerant circuit from the outlet of the evaporator to the suction port of the low-pressure stage compressor, and   the flow passage-switching mechanism is constituted by an on-off valve provided on the high-pressure supply passage and a valve, provided in a portion of the main refrigerant circuit from the outlet of the evaporator to the downstream end of the high-pressure supply passage, capable of blocking flow of the refrigerant from the high-pressure supply passage toward the evaporator.   
     
     
         4 . The refrigeration cycle apparatus according to  claim 1 , wherein
 the high-pressure supply passage has a downstream end connected to a portion of the main refrigerant circuit from the outlet of the evaporator to the suction port of the low-pressure stage compressor, and   the flow passage-switching mechanism is constituted by a three-way valve provided at the downstream end of the high-pressure supply passage.   
     
     
         5 . (canceled) 
     
     
         6 . The refrigeration cycle apparatus according to  claim 1 , further comprising:
 an activation detector that detects the activation of the expander or the low-pressure stage compressor, wherein   the controller switches control of the flow passage-switching mechanism from control before the activation to control after the activation, according to a detection result of the activation detector.   
     
     
         7 . The refrigeration cycle apparatus according to  claim 6 , wherein
 the activation detector includes a timer that measures an elapsed time from activation of the high-pressure stage compressor, and   when the time measured by the timer exceeds a specific threshold time, the activation of the expander or the low-pressure stage compressor is detected.   
     
     
         8 . The refrigeration cycle apparatus according to  claim 6 , wherein
 the activation detector includes a temperature detector that detects a difference between a temperature of the refrigerant at the suction port of the expander and a temperature of the refrigerant at the discharge port of the expander, and   when the temperature difference detected by the temperature detector exceeds a specific threshold, activation of the expander or the low-pressure stage compressor is detected.   
     
     
         9 . The refrigeration cycle apparatus according to  claim 6 , wherein
 the activation detector includes a pressure detector that detects a difference between a pressure of the refrigerant at the suction port of the expander and a pressure of the refrigerant at the discharge port of the expander, and   when the pressure difference detected by the pressure detector exceeds a specific threshold, activation of the expander or the low-pressure stage compressor is detected.   
     
     
         10 . The refrigeration cycle apparatus according to  claim 6 , wherein
 the activation detector includes a pressure detector that detects a difference between a pressure of the refrigerant at the suction port of the expander and a pressure of the refrigerant at the discharge port of the expander, and   when a value obtained by subtracting a current pressure difference detected by the pressure detector from a pressure difference that has been detected by the pressure detector at a time going back for a unit time exceeds a specific threshold, activation of the expander or the low-pressure stage compressor is detected.   
     
     
         11 . The refrigeration cycle apparatus according to  claim 6 , wherein
 the activation detector includes a temperature detector that detects a difference between a temperature of the refrigerant at the suction port of the expander and a temperature of the refrigerant at the discharge port of the expander, and   when a value obtained by subtracting a current temperature difference detected by the temperature detector from a temperature difference that has been detected by the temperature detector at a time going back for a unit time exceeds a specific threshold, activation of the expander or the low-pressure stage compressor is detected.   
     
     
         12 . The refrigeration cycle apparatus according to  claim 6 , wherein
 the activation detector includes a PTC heater provided in a portion from an outlet of the heat radiator to the suction port of the expander of the main refrigerant circuit, and   when the amount of change per unit time in an electric current flowing in the PTC heater exceeds a specific threshold, activation of the expander or the low-pressure stage compressor is detected.   
     
     
         13 . The refrigeration cycle apparatus according to  claim 6 , wherein
 the activation detector is a temperature detector that detects a temperature of the refrigerant at the discharge port of the low-pressure stage compressor, and   when a value obtained by subtracting a temperature that has been detected by the temperature detector at a time going back for a unit time from a current temperature detected by the temperature detector exceeds a specific threshold, activation of the expander or the low-pressure stage compressor is detected.   
     
     
         14 . The refrigeration cycle apparatus according to  claim 1 , wherein
 in the case where activation of the expander and the low-pressure stage compressor has been failed, the controller stops the high-pressure stage compressor and performs control to activate the expander and the low-pressure stage compressor again.   
     
     
         15 . The refrigeration cycle apparatus according to  claim 1 , wherein
 the expander and the low-pressure stage compressor are accommodated in a single closed casing.   
     
     
         16 . The refrigeration cycle apparatus according to  claim 1 , further comprising:
 a bypass flow passage that bypasses the expander; and   a bypass valve provided on the bypass flow passage, wherein   the controller opens the bypass valve to a specific degree before the activation of the expander and the low-pressure stage compressor and closes the bypass valve after the activation of the expander and the low-pressure stage compressor.   
     
     
         17 . The refrigeration cycle apparatus according to  claim 1 , wherein
 the expander and the low-pressure stage compressor each have a certain suction volume, and   the suction volume of the low-pressure stage compressor is larger than the suction volume of the expander.   
     
     
         18 - 30 . (canceled)