Refrigeration cycle apparatus

Abstract

In a refrigeration cycle apparatus that recovers power in an expander, obtaining a refrigeration cycle apparatus that is capable of reliably starting up the expander compared to conventional refrigeration cycle apparatuses. The refrigeration cycle apparatus includes a refrigerant circuit having a first compressor, a radiator, an expander and an evaporator connected in series with a piping; and a second compressor disposed between the first compressor and the radiator, the second compressor being driven by power recovered by the expander. The second compressor being a positive displacement compressor. The refrigeration cycle apparatus, further including a pressure regulating device (a bypass and an on-off valve) that maintains a pressure on a discharge side of the second compressor to be lower than a pressure on a suction side of the second compressor at least until the second compressor is started up.

1 . A refrigeration cycle apparatus, comprising:
 a refrigerant circuit connecting a first compressor, a first heat exchanger that serves as a radiator or a condenser, an expander, and a second heat exchanger that serves as an evaporator in series with a piping; and   a second compressor that is driven by power recovered by the expander;   a bypass bypassing either between a suction side of the second compressor and a suction side of the expander or between a discharge side of the second compressor and a discharge side of the expander; and   an on-off valve provided in the bypass, wherein   the second compressor is a positive displacement compressor,   the second compressor is connected to the first compressor in series, having one end of the bypass on its connection line, and   a pressure on a discharge side of the second compressor is lower than a pressure on a suction side of the second compressor with keeping the on-off valve as an opened state until the second compressor is started up.   
     
     
         2 . The refrigeration cycle apparatus of  claim 1 , wherein
 the second compressor is disposed between the first compressor and the first heat exchanger.   
     
     
         3 . The refrigeration cycle apparatus of  claim 2 , further comprising
 a check valve provided at a position, which is closer to the first heat exchanger than the connection point of the bypass, on a passage between the first heat exchanger and the expander, the check valve regulating a flow of the refrigerant to the first heat exchanger.   
     
     
         4 . The refrigeration cycle apparatus of  claim 1 , wherein
 the second compressor is disposed between the second heat exchanger and the first compressor.   
     
     
         5 . The refrigeration cycle apparatus of  claim 4 , further comprising
 a check valve provided at a position, which is closer to the second heat exchanger than the connection point of the bypass, on a passage between the second heat exchanger and the expander, the check valve regulating a flow of the refrigerant to the expander.   
     
     
         6 - 9 . (canceled) 
     
     
         10 . The refrigeration cycle apparatus of  claim 1 , further comprising:
 a heat medium sending device that sends a heat medium, which exchanges heat with the refrigerant flowing in the first heat exchanger, to the first heat exchanger, wherein   at least until the second compressor is started up,   the rotation speed of the heat medium sending device is reduced under the target rotation speed or the heat medium sending device is stopped.   
     
     
         11 . The refrigeration cycle apparatus of  claim 1 , wherein the refrigerant flowing in the refrigerant circuit is carbon dioxide.