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在冷凝温度70～130℃、循环温升40～65℃的工况范围内,以HFC245fa为工质,考察了单、双级节流中间不完全冷却与完全冷却等4种两级循环方式下的中高温热泵循环性能。结果表明:4种两级循环方式下COP(综合性能系数)均较单级循环明显提高,其中两级节流中间不完全冷却方式带来的COP改善幅度最大,为12.04%～33.25%;COP改善幅度随循环温升增大而单调上升、随冷凝温度升高先减小后增大。两级循环方式还有助于降低压缩机排气温度,对于以湿流体为工质的情形,效果尤为显著。综合考虑性能收益与系统代价,对中高温热泵引入两级循环方式具有可行性。
In the condition of condensing temperature of 70 ~ 130 ℃ and circulating temperature rise of 40 ~ 65 ℃, using HFC245fa as the working fluid, four kinds of two-stage circulation modes, single and double-stage throttling intermediate incomplete cooling and complete cooling, were investigated Of the high temperature heat pump cycle performance. The results show that COP (comprehensive coefficient of performance) is significantly higher than that of single stage in four kinds of two-stage circulation modes, of which the COP improvement caused by the incomplete cooling mode with the two-stage throttling is the largest, ranging from 12.04% to 33.25% The improvement amplitude increases monotonically with the increase of temperature, decreases first and then increases with the increase of condensation temperature. The two-stage cycle also helps to reduce the compressor discharge temperature, especially for wetted fluids. Taking into account the performance benefits and system costs, it is feasible to introduce two-stage circulation mode in high-temperature heat pump.