| 摘要 |
PROBLEM TO BE SOLVED: To prevent degradation of the coefficient of performance in a heat pump cycle, while the necessary amount of an lubricating oil is secured in a heating operation. SOLUTION: Heat exchange is conducted between a discharge side refrigerant and a suction side refrigerant, even during heating operation. Thus, liquid refrigerant, containing much lubricating oil in the suction side refrigerant, is heated by the discharge side refrigerant to evaporate the liquid refrigerant, even in heating operation. Thus, the amount of liquid refrigerant sucked in compressor 110 can be reduced. Accordingly, while preventing increase in the compression work of the compressor 110, the opening area of an oil return hole 144 can be enlarged to the extent to secure an optimum amount of the lubricating oil in the heating operation. Since the enthalpy of the discharge side refrigerant can be decreased through the heat exchange between the discharge side refrigerant and the suction side refrigerant, heat quantity contributing to air conditioning can be increased, in either case of cooling or heating operations.
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