二次抽汽回热式有机朗肯循环系统热力性能分析

Thermodynamic performance analysis of graded regenerative extraction organic Rankine cycle system

以R365mfc和R245ca作为循环工质,设计了低温余热驱动的二次抽汽回热式有机朗肯循环系统。采用REFPROP 8.0制冷剂物性计算软件及MATLAB对该回热系统的热力性能进行计算,并对系统最佳抽汽压力的3种备选方案进行比较。结果表明:以冷凝器出口温度和蒸发器进口温度的3分点温度对应的饱和压力作为抽汽压力(方案3)所对应的系统热效率最高,而采用汽轮机进出口焓值等分点对应压力作为抽汽压力(方案1)所对应的系统单位工质做功能力最大;随着工质蒸汽过热度增大,系统热效率减小,但减小幅度较小,因此,二次抽汽回热式有机朗肯循环系统无需通过增加过热度来提高系统热效率。

Using R245 ca and R365 mfc as the working fluid,a secondary regenerative extraction organic Rankine cycle system driven by low temperature waste heat was designed.The MATLAB software and REFPROP 8.0software for refrigerants＇ physical property（offered by NIST）calculation and were applied to analyze the thermodynamic performance of this regenerative system.Moreover,three candidate schemes for the optimum extraction pressure were compared.The results show that,the system applying scheme III has the highest heat efficiency,in which the saturation pressure corresponding to the trisection temperature of the condenser outlet temperature and the generator inlet temperature is taken as the extraction steam pressure.The system applying scheme I has the best ability to work,in which the pressure corresponding to the trisection enthalpy at the steam turbine inlet and outlet is taken as the extraction steam pressure.As the degree of superheat of the steam increases,the heat efficiency and exergy efficiency of the system reduces with low rate.Therefore,the heat efficiency and exergy efficiency of the graded regenerative extraction organic Rankine cycle system can be increased without increasing the degree of superheat of the steam.