混合工质ORC耦合CO2跨临界发电系统性能研究

Study on Performance of Coupled Power Generation System with Hybrid ORC and CO2 Trans-Critical Cycle

中文关键词: CO2跨临界循环  耦合系统  蒸发温度  热源温度  跨临界蒸发压力

英文关键词: CO2 trans-critical cycle  coupled system  evaporation temperature  heat source temperature  CO2 transcritical evaporation pressure

中文摘要:

      为了实现低温热能的充分回收利用,在混合工质ORC循环发电基础上,提出一种利用CO2跨临界循环与其耦合的发电系统。基于热力学第一、第二定律,建立相应热力学模型,并编写计算程序,确定系统运行条件,分析蒸发温度T1、跨临界蒸发压力p01及热源温度Tg等参数变化对耦合系统性能的影响,并将其与采用相同混合工质的ORC系统进行比较。结果表明：随蒸发温度提高,跨临界循环部分输出功逐渐增加,而ORC部分由于冷凝温度提升所减少的输出功逐渐降低。在Tg=373.00K时,若T1= 340.00K、354.00K,耦合系统较基本ORC系统输出功分别增加15.77kW、113.53kW。随跨临界蒸发压力p01变化,耦合系统输出功及?效率均有先减小后增加再降低的规律,存在一最佳跨临界压力,且表现为随热源温度降低,耦合系统性能优越性逐渐明显。若Tg=373.00K或403.00K,则耦合系统较基本ORC系统分别增加19.16、7.18kW。在蒸发温度较高或热源温度较低时,采用耦合系统具有重要意义。

英文摘要:

      Organic Rankine cycle（ORC）has been identified as a suitable technological option for recovering heat in industrial processes and converting low-grade heat into electricity. A novel coupled ORC power generation system using zeotropic mixtures and CO2 as working fluid is presented for further increasing thermal performance.The analytical model is investigated from the viewpoints of the energy and exergy. The evaporation temperature, trans-critical evaporation pressure, and the heat source temperature are considered as restrictive conditions. Both the coupled ORC and ORC using the same zeotropic mixture are considered as research subjects. The results indicate that with the increase of the evaporation temperature, the output power of the trans-critical cycle is increased gradually, but the power of the ORC subsystem reduced gradually. The coupled system can be increased by 15.77kW and 113.53kW respectively when the evaporation temperature is 340.00K and 354.00K and the heat source temperature is 373.00K.With the increase of the trans-critical evaporation pressure, the output power and the energy efficiency of the coupled system behave as that which decreases at first and then increases, finally reduces again.There exists an optimum trans-critical evaporation pressure and the advantage of the coupled system definite improvement if the heating temperature decreases gradually. The coupled system increases by 19.16 and 7.18kW to the simple ORC system if the heat source temperature is 373.00K and 403.00K.Besides, the coupled system is beneficial to higher evaporation temperature and lower heat source temperature.