超/亚临界ORC联合发电系统热力性能分析

Thermodynamic Analysis for Power Generation System with Combined Supercritical and Subcritical Organic Rankine Cycle

本研究在单纯超临界、亚临界的ORC(有机朗肯循环)发电系统基础上,提出一种新型超临界、亚临界ORC联合发电系统,并建立其理论模型。通过编制计算机程序,分别对单纯超临界、亚临界ORC以及新型联合发电系统的热力性能进行比较。结果表明:采用R143a、R245fa作为联合系统的两循环区工质,当依次单独改变超临界、亚临界区蒸发压力时,各循环区质量流量变化与单纯超临界、亚临界ORC相似。前者随蒸发压力的增大而逐渐递增,后者则呈相反变化趋势,联合发电系统的热力性能均优于单纯超临界、亚临界ORC。同时随两循环区蒸发压力的增大而不断提高,但增幅减小,且提高超临界区蒸发压力可使系统热力性能最佳。采用R134a、R245fa作为系统两循环区有机工质,可使联合发电系统火用损失达到最小。

To further recover the waste heat produced in the process of mineral mining with steam injection,a combined system of supercritical and subcritical Organic Rankine Cycles( ORC) was proposed and corresponding model was established. The thermodynamic analysis of single supercritical ORC,single subcritical ORC,and the newly proposed combined system was performed and compared. The results show that with R143 a and R245 fa as working fluids for the supercritical and subcritical cycles of the combined system,respectively,the mass flow rate variation with the evaporator pressure of each cycle in the combined system is similar to that of corresponding single ORC; the supercritical ORC gradually increases with the evaporator pressure,while the subcritical ORC has opposite trend. The net power output,thermal efficiency and exergy efficiency of the combined system,however,is better than both single ORC systems,and increases with supercritical and subcritical evaporator pressures. The increase in the supercritical evaporator pressure can result in optimum thermodynamic performance. The comparison of four different working fluids indicates that using R134 a and R245 fa as working fluids for the supercritical and subcritical cycles of the combined system minimizes the exergy loss.