有机朗肯循环系统最佳蒸发温度和分析

随着能源问题日益突出,低温烟气余热深度利用成为了研究热点领域。其中,有机朗肯循环是实现低品位余热转换为电能的一有效途径。基于热力学基本定律,以有机朗肯循环系统最大做功能力和效率为目标函数,计算分析了10种不同工质在亚临界状态下以上两种目标函数的特性。结果表明,每种工质均存在一最佳蒸发温度使循环净输出功最大,而且工质临界温度越高,对应的最佳蒸发温度也越高;热源温度相同时,系统效率随窄点温差增大而减小;同一窄点温差时,当热源温度不超过临界温度两倍的窄点温差时,效率有一最大值;反之,则随蒸发温度升高不断增大。这些将为有机朗肯循环工质选择和性能优化提供理论指导。

Optimal evaporating temperature and exergy analysis for organic Rankine cycle

Since energy issues become increasingly urgent in the world,considerable interest has focused on the utilization of low-grade waste heat.Organic Rankine cycle(ORC) is one of the effective routes to transform the low-grade waste heat to electricity.In this study,the maximum useful output work and exergy efficiency of the ORC are selected as the objective functions.10 different working fluids are chosen to comprehensively investigate and analyze the important characteristics of the two objective functions in the subcritical state.The results show that an optimal evaporating temperature exists for each working fluid,at which the useful work is the maximum.Moreover,the higher the critical temperature,the higher the optimal evaporating temperature.It is found that for the same heat source,the exergy efficiency decreases with the increase of the pinch point temperature difference.For the same pinch point temperature difference,the exergy efficiency has a maximum value when the heat source inlet temperature is twice of the pinch point temperature difference lower than the critical temperature.Otherwise,the exergy efficiency keeps increasing with the heat source temperature.These results provide some valuable guidance to optimize the ORC system and screen working fluid.