非共沸工质有机朗肯循环的热力学分析

Thermodynamic Analysis of Organic Rankine Cycle with Zeotropic Mixtures

通过热力学推导,给出了基于Jacob数和蒸发冷凝温度之比来预测理想非共沸工质有机循环热效率和输出功的理论公式,同时与利用Matlab编程计算的数值计算模型进行了对比.同时以空气作为热源,采用水冷的方式,以R227ea/R245ca作为工质,研究了不同的冷却水温升和冷却水进口温度对其不同质量分数下的输出功的影响.结果发现,当冷却水温升小于工质的温度滑移时,二者相等时存在输出功的当地最大值;当冷却水温升大于工质的温度滑移时,温度滑移最大时存在输出功的最大值。在相同的冷却水温升下,冷却水的进口温度越低,工质相同质量分数下输出功越高,同时最大输出功对应的工质质量分数不变。

In this paper,a thermodynamic model which mainly includes Jacob number and the ratio of evaporation temperature and condensation temperature is proposed to forecast the thermal efficiency and output work of ORC system with zeotropic mixture.Furthermore,a numerical model programmed by Matlab 2010 a is used to verify the previous thermodynamic model.Then,using the air as the heat source and the water as the heat sink,we investigate the influence of cooling water temperature increase and inlet temperature on the output work of ORC system with zeotropic mixture R227ea/R245 ca of different mass fractions as the working fluid.Results show that if the cooling water temperature increase is less than the maximum temperature glide of R227ea/R245 ca,the maximum value of output work is obtained when the cooling water temperature increase is equal to temperature glide,and the cooling water temperature increase is more than the maximum temperature glide of R227ea/R245 ca,the maximum value of output work is obtained at the mass fraction corresponding to the maximum temperature glide.With the same cooling water temperature increase,the lower the cooling water inlet temperature is,the larger output work at the same mass fraction of R227ea/R245 ca is.At the same time,the mass fraction corresponding to the maximum output work is basically unchanged.