耦合跨临界与亚临界有机朗肯循环性能分析

Performance Analysis of a Coupled Transcritical and Subcritical Organic Rankine Cycle

提出了一种回收烟气余热的耦合跨临界与亚临界有机朗肯循环系统,并进行了详细的性能分析。结果表明,该系统可以使膨胀机压比和进口压力降低,工质的选择更加灵活;当中间换热器节点温差小于某一临界值时,耦合系统的热力学性能要优于单级跨临界有机朗肯循环,且存在一个最佳节点温差使得系统发电成本最低;随着工质临界温度的增加,耦合系统的热力学性能会得到改善;使用等熵工质时系统性能要优于使用干工质时系统性能。

This paper presents a novel CORC(coupled organic Rankine cycle) system used to recover the waste heat of the flue gas,which coupled a TORC(transcritical organic Rankine cycle) with a SORC(subcritical organic Rankine cycle).Based on the classical thermodynamic theory,a detailed performance analysis on the novel CORC system is performed.The results show that the pressure ratio of the expander is decreased and the section of the working fluids becomes more flexible and abundant in the CORC system.When the pinch point temperature difference of the internal heat exchanger is less than a critical value,the performance of the CORC system overmatches that of the TORC.There is an optimal pinch point temperature difference of the internal heat exchanger,which corresponds to the minimum electricity production cost.With the increase of the critical temperature of the working fluid,the performance of the CORC system is improved.Furthermore,The CORC system using isentropic working fluids exhibits better performance than one using dry working fluids.