| 摘要 |
A reverse air cycle type heat pump is provided that utilizes unidirection refrigerant flow wherein the condenser and evaporator retain their functions, but the air directed across them is redirected for different operations. The air cycle type heat pump is further provided with a secondary defrost circuit including valves which permit refrigerant flow to by-pass the compressor and the expansion device only when compressor operation terminates and the system pressure differential is equalized. This defrost circuit causes the relatively warm refrigerant in gaseous phase in the condenser to displace the relatively cold refrigerant in liquid phase in the evaporator with the flow continuing until the defrost system is completed.
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