| 摘要 |
PROBLEM TO BE SOLVED: To shorten defrost time by disposing a heater between an expansion mechanism and a heat source and performing defrost operation in forward cycle or reverse cycle thereby improving defrost efficiency. SOLUTION: A compressor 10, a heat source side heat exchanger 11, an expansion mechanism 12 and a using side heat exchanger 13 are coupled sequentially through refrigerant tubing 20 to constitute a refrigerant circuit 21. A heater 16 for heating refrigerant flowing through the refrigerant tubing 20 is disposed between the expansion mechanism 12 and the heat source side heat exchanger 11. During defrost operation, refrigerant delivered from the compressor 10 is fed from the using side heat exchanger 13 toward the heat source side heat exchanger 11 in forward cycle and the heater 16 is operated. Since thermal conductivity is high as compared with a case where heat is transmitted to gas phase refrigerant and efficient heating can be effected, efficiency of defrost operation can be enhanced.
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