Abstract: Most studies on organic Rankine cycle (ORC) mainly focused on the thermodynamic properties of working medium. Pinch analysis method used commonly may lead to different evaluation criteria in different medium. This paper preselected fluids by their properties in the consideration of environment protection，safety and stability to solve the problems mentioned above. Fourteen types of working fluids were selected and screened by the thermodynamic and economic properties，and the optimal working fluid was obtained using Matlab and Refprop simulation. The working substance evaluation standards were unified according to the properties of unit power required for UA and mass flow rate. The results showed that most alkane substances had higher thermal efficiency，compression ratio and lower mass flow. The cyclohexane was an ideal circulating working fluid with higher thermal efficiency，lower mass flow rate and appropriate pressure ratio in the low temperature waste heat system.

Key words: exergy, organic Rankine cycle, flue gas waste heat, organic working fluid, thermal efficiency, simulation, optimization

摘要： 目前对有机朗肯循环的研究主要集中在工质的热力学特性方面，但尚不全面，普遍使用的热力循环性能的评价方法（窄点分析法）也存在不同工质评价标准不一的问题。为解决这两个问题，本文从环保、安全和稳定性方面对工质进行预选，得到R600、R245fa、2,2-二甲基丙烷、R123和苯等14种有机工质，而后从热力学特性和经济性两方面对初选工质进行优选，通过Matlab和Refprop模拟优化得出适合此系统的最佳工质。其中，以单位功量UA和单位功量质量流量为性能指标，统一了工质评价标准。结果表明：大部分烷类工质的热效率和压比相对其他类工质较高，而所需质量流量远小于其他类工质，且烷类工质环己烷以其较高的热效率、较低的单位功量质量流量和UA等特性，被认为是低温余热回收系统中较理想的循环工质。

关键词: 有机朗肯循环, 烟气余热, 有机工质, 热效率, 模拟, 优化