Thermodynamic analysis of three ejector based organic flash cycles for low grade waste heat recovery
Thermodynamic analysis of three ejector based organic flash cycles for low grade waste heat recovery
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用于低品位余热回收的基于三种喷射器的有机闪蒸循环的热力学分析
DOI：
10.1016/j.enconman.2019.02.016
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发表时间：
2019-04
影响因子：
10.4
通讯作者：
Wang Feng Xiang
中科院分区：
文献类型：
--
作者：
Chen Long Xiang;Hu Peng;Sheng Chun Chen;Zhang Nan;Xie Mei Na;Wang Feng Xiang
基于有机闪蒸循环（OFC）的系统由于冷热传热曲线的更好匹配而在废热回收应用中是有前途的技术。然而，节流过程中大量的火用损失，导致OFC的热效率较低。本文在基本型OFC中引入喷射器，分别取代低压节流阀、高压节流阀和两个节流阀，即单喷射器单闪蒸OFC（SESF-OFC）、单喷射器双闪蒸OFC（SEDF-OFC）和双喷射器双闪蒸OFC（DEDF-OFC）。利用稳态数学模型和热力学定律，进行了热力学分析，包括能量分析、火用分析、参数分析和比较分析。喷射器允许高压流体夹带低压流体并将低压流体压缩到中压。因此，可以提高涡轮机的质量流率或膨胀比，从而使得三种基于喷射器的OFC都比基本OFC更高效。当以453.15 K高温流体为热源时，DEDF-OFC的第二定律效率（ηII，G）最大，为38.95%，其次是SEDF-OFC（37.92%）、SESF-OFC（33.68%）和基本OFC（31.43%）。SEDF-OFC的效率高于SESF-OFC，表明用喷射器代替高压节流阀比低压节流阀更有效。与传统有机朗肯循环（ORC）进行了比较，结果表明：基本OFC和SESF-OFC的ηII、G均低于ORC，而SEDF-OFC和DEDF-OFC的效率高于ORC，SEDF-OFC和DEDF-OFC的平均增量分别为10.37%和15.01%。因此，基于喷射器的OFC是用于具有高效率的废热回收应用的替代方法。
Systems based on Organic Flash Cycle (OFC) are promising technologies for waste heat recovery application due to a better match of the hot and cold heat transfer curves. However, the large amount of exergy lost during the throttling process, results in a low thermal efficiency for OFC. In this work, ejectors are introduced in basic OFC to replace the low pressure throttle valve, high pressure throttle valve and both two throttle valves, which namely Single Ejector and Single Flash evaporator based OFC (SESF-OFC), Single Ejector and Double Flash evaporators based OFC (SEDF-OFC) and Double Ejectors and Double Flash evaporators based OFC (DEDF-OFC), respectively. The thermodynamic analysis including energy analysis, exergy analysis, the parametric analysis and comparison analysis are evaluated by using steady-state mathematical model and thermodynamic laws. The ejector allows a high pressure fluid to entrain and compress a low pressure fluid to a medium pressure. Hence, the mass flow rate or expansion ratio of turbine can be enhanced, results in all of three ejector based OFCs are more efficient than the basic OFC. When the high temperature fluid with temperature of 453.15 K is set as heat source, the maximum global second law efficiency (ηII,G) of 38.95% belongs to DEDF-OFC followed SEDF-OFC (37.92%), SESF-OFC (33.68%) and basic OFC (31.43%). The SEDF-OFC is more efficient than SESF-OFC, which indicates that the high pressure throttle valve replaced by ejector is a more effective method than the low pressure throttle valve done. Moreover, the four OFCs have been compared with conventional Organic Rankine Cycle (ORC), and the comparison results show that theηII,Gof basic OFC and SESF-OFC are lower than that of ORC, while SEDF-OFC and DEDF-OFC are more efficient than ORC, and the average increment of SEDF-OFC and DEDF-OFC are 10.37% and 15.01%, respectively. Hence, the ejector based OFCs are alternative methods for waste heat recovery application with a high efficiency.
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