非共沸混合工质用于C-ORC系统的热力学分析

Thermodynamic Analysis of C-ORC System with Zeotropic Mixture

以低温烟气为热源,以R245fa、R152a及不同比例R245fa/R152a混合物为工质,提出新型的再热-抽汽-内回热联合有机朗肯循环（C-ORC）系统,基于美国NIST提供的制冷剂物性参数查询软件（REFPROP）及数学处理软件（MATLAB）混合编程,以净输出功和热效率为主要目标参数,分析系统性能随抽汽回热器出口温度、再热温度、不同比例混合工质的变化关系。结果表明,相同蒸发温度下纯工质R245fa的热力性能优于R152a,其最佳的抽汽回热器出口温度分别为70和55℃,抽汽回热器出口温度对系统的影响要大于再热温度的影响;混合工质分析中,在70℃抽汽回热器出口温度、105℃再热温度下,存在R245fa/R152a最佳质量分数比0.85/0.15,对应的净输出功为37.18 kW、热效率为18.52%、损为30.08 kW,其中蒸发器、冷凝器所占的损最大。

On the basis of using low temperature heating-regenerative-internal regenerative organic flue gas as the heat source,the new type combined re- Rankine cycle （C-ORC） system was proposed with R245fa,R152a,and their zeotropic binary mixture with different mass fraction as the working fluids. The variation of system performance with extraction steam recuperator outlet temperature, reheating tempera- ture or mixing working medium with different proportion was analyzed with net output power and thermal efficiency as the main parameters of system performance, by using the mixed programming with REFPROP provided by NIST and MATLAB. Results showed that R245fa was greatly superior to R152a in terms of thermodynamic performance with the same evaporation temperatures, and their optimal extraction steam recuperator outlet temperatures are 70 ℃ and 55 ℃ respectively. Extraction steam recuperator outlet tem- perature has greater influence on C-ORC thermodynamic performance than reheating temperature. With the mixtures as the working fluid, there is an optimal R245fa/R152a mass fraction ratio of 0.85/0.15 for the extraction steam recuperator outlet temperature of 70 ℃ and reheating temperature of 105 ℃, and the calculated net output power,thermal efficiency and exergy loss are 37.18 kW,18.52% and 30.08 kW. Exergy loss, mostly take places in evaporator and condenser