二元非共沸混合工质泄漏对有机朗肯循环性能及环境的影响

发布时间：2018-01-27 04:52

本文关键词： 有机朗肯循环混合工质泄漏环境火用成本经济性补液　出处：《重庆大学》2016年硕士论文　论文类型：学位论文

【摘要】：有机朗肯循环(Organic Rankine Cycle,ORC)由于设备简单、操作方便等优点,近年来在低品位能源利用方面获得迅速发展,是目前低品位能源开发利用技术研究的重点。利用非共沸混合工质的温度滑移‖优势,能实现工质在换热设备中与冷热源进行较好地温度匹配,从而减少换热器中由传热温差引起的不可逆损失。但有机工质具有一定的全球变暖潜值、臭氧层损害潜值等环境影响,在HVAC(采暖空调)领域,有机工质泄漏引起的工质组分以及循环性能的变化已受到普遍关注和研究,由于ORC采用同类有机工质,因此工质泄漏对循环性能乃至环境的影响值得重视和加以研究。本文采用二元非共沸混合物R245fa/R601a和R114/R123为循环工质,对ORC系统蒸发器、冷凝器不同部位、泄漏率为0~30%的泄漏影响进行了分析,在此基础上建立了考虑泄漏工质环境影响的系统火用平衡模型,用环境火用成本对混合工质泄漏造成的环境影响进行量化分析,并对ORC系统平准化能量产出成本(Levelized Energy Cost,LEC)的评估方法提出修正,最后,根据二元非共沸混合工质ORC的实际生产需要,提出补液配比方案。主要结论如下:(1)非共沸混合工质泄漏将引起ORC运行工质配比变化,从而导致ORC系统性能偏离设计值。发生汽相泄漏时,高沸点组分比例增加,而发生液相泄漏时,低沸点组分比例增加。汽相泄漏引起的工质配比变化率比液相泄漏的大。(2)非共沸混合工质泄漏对ORC系统性能有较大影响。用综合环境影响火用效率评价ORC系统热力学性能,泄漏率为10%时,以R245fa/R601a(0.6/0.4)为循环工质的火用效率减小3.9%,以R114/R123(0.8/0.2)为工质的火用效率减小30%。靠近冷凝器出口的汽相泄漏对ORC系统性能影响最大。(3)考虑混合工质泄漏对ORC发电成本有较大的影响。当泄漏率为10%时,以R245fa/R601a(0.6/0.4)为循环工质的ORC系统,考虑泄漏环境影响的LEC值比不考虑泄漏时增大10.4%(汽相泄漏)和8.3%(液相泄漏),以R114/R123(0.8/0.2)为循环工质时,考虑泄漏环境影响的LEC比不考虑泄漏时增加89.8%(汽相泄漏)和81.6%(液相泄漏)。(4)对发生混合工质泄漏之后的ORC系统进行补液时,需要根据泄漏后的工质配比计算补液配比。以R245fa/R601a(0.6/0.4)为例,当泄漏率为10%,对系统性能影响较大的四种泄漏发生后的补液配比应为0.38/0.62、0.35/0.65、0.64/0.36和0.66/0.34,不能简单地按照原配比0.6/0.4进行充注。
[Abstract]:Organic Rankine cycle ORC (Organic Rankine cycle ORC) has been developed rapidly in recent years because of its simple equipment and convenient operation. It is the focus of the research on the technology of low grade energy development and utilization at present. By using the advantage of non-azeotropic mixture of working fluids, it can achieve a better temperature matching between refrigerant and heat source in heat exchange equipment. In order to reduce the irreversible loss caused by the heat transfer temperature difference in the heat exchanger, but the organic working fluid has some environmental effects, such as global warming potential, ozone layer damage potential, in the field of HVAC (heating air conditioning). The changes of the components and cyclic properties of organic refrigerants caused by leakage of organic working fluids have been widely concerned and studied, because of the use of similar organic working fluids in ORC. Therefore, the effects of working fluid leakage on cycling performance and environment should be paid attention to and studied. In this paper, binary non-azeotropic mixtures R245fa / R601a and R114 / R123 are used as circulating working fluids. Based on the analysis of leakage effect of different parts of ORC system evaporator and condenser with leakage rate of 0 ~ 30%, a system exergy balance model considering the environmental impact of leakage working fluid is established. Environmental exergy cost is used to quantitatively analyze the environmental impact caused by the leakage of mixed working fluid, and to equalize the energy output cost of ORC system to the level Energy Cost. Finally, according to the actual production needs of binary non-azeotropic mixture ORC. The main conclusion is as follows: 1) the leakage of non-azeotropic mixture will cause the change of the working fluid ratio of ORC, which will cause the performance of ORC system to deviate from the design value. When the vapor phase leakage occurs, the performance of the ORC system will deviate from the design value. The ratio of high boiling point component increases, but the liquid phase leakage occurs. The ratio of low boiling point component increased. The change rate of working medium ratio caused by vapor phase leakage was larger than that of liquid phase leakage. The leakage of non-azeotropic mixture has great influence on the performance of ORC system. The thermodynamic performance of ORC system is evaluated by comprehensive environment influence exergy efficiency. When the leakage rate is 10, the exergy efficiency of R245faR / R601a0. 6 / 0. 4) as the circulating working medium is reduced by 3.9%. The exergy efficiency of R114 / R1230.8 / 0.2) was reduced by 30%. The vapor phase leakage near the condenser outlet had the greatest effect on the performance of ORC system. Considering the leakage of mixed working fluid has a great influence on the cost of ORC power generation. When the leakage rate is 10. A ORC system with R245FAR / R601a / 0.6 / 0.4) as the circulating working medium. The LEC value considering the environmental effects of leakage increases by 10.4 (vapor phase leakage) and 8.3 (liquid phase leakage) than when leakage is not considered. When R114 / R123N / 0.8 / 0.2) is used as a circulating working medium. LEC with environmental effects of leakage increased 89.8% and 81.6% respectively (liquid phase leakage) and 81.6% (liquid phase leakage) than when leakage was not considered. The rehydration of the ORC system after the leakage of the mixed working fluid is carried out. It is necessary to calculate the rehydration ratio according to the working fluid ratio after leakage. Take R 245fa / R 601a 0. 6 / 0. 4) as an example, when the leakage rate is 10%. The rehydration ratios of the four kinds of leakage which have a great influence on the system performance should be 0.38 / 0.62U / 0.35 / 0.65N / 0.64 / 0.36 and 0.66 / 0.34 respectively. It can not simply be filled with the original ratio of 0.6 / 0.4.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TK115

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