具有回热特性的双级压缩高温热泵系统热力学性能分析及研究

Analysis on thermodynamic performance of a two-stage compression high-temperature heat pump system with regenerative characteristics

针对电力工业中余热回收再利用,传统两级压缩热泵系统在较大压比及高冷凝温度条件下作业,容易导致压缩机发生液击现象,造成系统能效系数CCOP下降、压缩机使用寿命降低等问题,本文在系统中设置中间回热器,重新构建出了具有回热特性的新型系统,并通过定义工质液击斜率及系统压焓变化斜率,有效判定新型系统是否出现液击以及工质的排气过热度,对比分析了传统两级压缩系统与新型系统的热力学性能以及经济性。结果表明:当工作介质为R236ea,工作温差为65 K、冷凝温度为393.15 K时,新型两级回热完全冷却系统的CCOP相比传统两级压缩完全冷却热泵系统高2.93%,并且在压缩机不发生液击的前提下排气过热度仅为5.68 K。此外,该系统在单位质量流量循环工质作业下,压缩机的总所需容积仅为0.0317 m^(3),在同等作业条件下有效降低了压缩机能耗。

In view of the waste heat recovery and reuse in power industry,the conventional two-stage compression heat pump system works under the conditions of large pressure ratio and high condensation temperature,which easily leads to the liquid hammer phenomenon of the compressor,resulting in the decrease of CCOP and the service life of the compressor.For this reason,a new type of system with regenerative characteristics is reconstructed by setting an intermediate regenerator in the system.By defining the liquid hammer slope of working medium and the pressure enthalpy change slope of the system,it can effectively determine whether there exists liquid hammer in the new system and the exhaust superheat of working medium.The thermodynamic and economic performance of the conventional two-stage compression system and the new system are compared.The results show that,when the working medium is R236ea,the working temperature difference is 65 K and the condensation temperature is 393.15 K,the CCOP of the new two-stage regenerative complete cooling system is 2.93%higher than that of the conventional two-stage compression complete cooling heat pump system,and the exhaust superheat is only 5.68 K on the premise of no liquid hammer in the compressor.In addition,under the working fluid operation of unit mass flow,the total required volume of the compressor is only 0.0317 m^(3).The energy consumption of the compressor is effectively reduced under the same working conditions.