A cascaded heat exchange geothermal Organic Rankine Cycle (ORC) system is proposed.R601/R236ea is used as working fluid,certain temperature geothermal energy and cooling water are selected as the heat source and heat sink of this system with the given minimum temperature difference for the evaporator and condenser.With net power output as objective function,the system is optimized to its optimal operating conditions by applying Matlab software and using a function that calls REFPROP,and a comparison of the thermal performance between this system and basic ORC system is carried out.The results show that the mean transferring heat temperature difference between the heat source and the working fluid in the evaporator decreases in this system compared with the basic ORC system,which results in less thermodynamic irreversibility and reduces the heat source emission temperature under the optimal working conditions;the thermal performance of this system is higher than that of the basic ORC system,and the increasement of net power output and exergy efficiencies is 12.09％.%提出了一种基于ORC梯级换热的地热发电系统.以地热能作为热源,选取R601/R236ea作为循环工质,在给定冷热源入口参数,以及给定的蒸发器和冷凝器最小换热温差下,以系统循环净功为目标函数,采用Matlab软件并调用REFPROP编制计算程序进行参数优化,与基本ORC发电系统进行比较.结果显示:在最优工况下,与基本ORC发电系统相比,基于ORC梯级换热发电系统可有效减小工质在换热过程中的换热温差,减少换热不可逆损失;同时降低热源排放温度,提高热源使用率;循环净功和火用效率可提高12.09％.
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