To solve a problem wherein coolant flowing through a duct line bypassing an expander does not contribute to improvement of system efficiency at all, as the coolant causes an isoentropic change when it comes out from an outlet of a radiator and joins coolant from an outlet of the expander.
A compressor 101, a radiator 102, an expander 103, and an evaporator 104 are serially connected in this order. In this configuration, by flowing the coolant into a first bypass circuit 106 connecting a suction line of the expander 103 and the compressor 101 via a first flow rate control valve 105, an amount of coolant circulation of the radiator 102 can be increased while avoiding constraint of "constant density ratio" so as to optimally control the degree of superheat, which can improve performance of the whole refrigeration cycle device.
Hiroki Naito
Daisuke Nagano