低温热源喷射式发电制冷复合系统的分析

Exergy Analysis of a Combined Power and Ejector Refrigeration Cycle Driven by Low-temperature Heat Sources

根据热力学第二定律,对一种新型低温热源喷射式发电制冷复合系统进行了分析,并以R600a作为工质对系统进行了仿真计算.结果表明:在热源入口温度为420 K、热源热水流量为0.2kg/s、热源蒸发温度为370 K的标准工况下,系统净发电量为2.74 kW,系统制冷量为11.99 kW,系统的效率达到25.83%,系统能量利用率为45.34%;系统损失主要发生在蒸汽发生器和喷射器中.在热源蒸发温度提高过程中,系统内部工质流量发生改变,导致系统净发电量和效率小幅下降,制冷量和能量利用率先增后降.当热源蒸发温度为370 K时,系统能量利用率达到最大值.

Exergy analysis was carried out for a novel combined power and ejector refrigeration cycle driven by low-temperature heat sources based on the second law of thermodynamics,while a numerical simulation performed for the system using R600a as the working fluid.Results show that under typical heat source conditions such as the inlet temperature Ths=420 K,mass flow m ·hs=0.2 kg/s and generating temperature Tg=370 K,the system may produce 2.74 kW of net power output（Wnet）,11.99 kW of refrigeration output（Qe）,with an exergy efficiency ηexergy up to 25.83% and energy utilization efficiency ηu up to 45.34%.The cycle exergy loss mainly occurs in the steam generator and ejector.When Tg increases,both Wnet and ηexergy drop slightly,whereas Qe and ηu show a trend of first increase and then decrease due to the variation of mass flow.The energy utilization efficiency ηu reaches maximum while Tg=370 K.