| 摘要 |
It is an object of the present invention to reduce the constraint that the density ratio is constant as small as possible, and to obtain high power recovering effect in a wide operation range by using an expander which is operated in accordance with a flowing direction of refrigerant. A determining method of a high pressure of a refrigeration cycle apparatus in which a refrigeration cycle uses carbon dioxide as refrigerant and has a compressor, an outdoor heat exchanger, an expander and an indoor heat exchanger, and the refrigeration cycle including a bypass circuit provided in parallel to said expander, and a control valve which adjusts a flow rate of refrigerant flowing through said bypass circuit, said compressor being driven by power recover by said expander, wherein if an optimal high pressure of a first refrigeration cycle flowing through said expander and a second refrigeration cycle flowing through said bypass circuit is defined as Ph, and a bypass amount ratio flowing through said bypass circuit in said Ph is defined as Rb0, and a maximum refrigeration cycle efficiency of said first refrigeration cycle in said Ph is defined as COPe, and a maximum refrigeration cycle efficiency of said second refrigeration cycle in said Ph is defined as COPb, the optimal high pressure Ph which maximizes (1-Rb0)xCOPe+Rb0xCOPb is determined.
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