It is shown that there exists an optimum mean temperature in evaporator condenser to maximize the COP of the system, and the maximal COP of the system is increased with lowering the condensing temperature.

• 高温级冷凝温度改变时 ；循环性能系数也要随之变化 ；随冷凝温度增加 ；系统达到最大性能系数时的最大中间温度也增加 .