CIESC Journal ›› 2014, Vol. 65 ›› Issue (12): 4655-4663.DOI: 10.3969/j.issn.0438-1157.2014.12.002

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Influence of pinch point temperature difference and fluid properties on trans-critical organic Rankine cycle

YU Chao, XU Jinliang, MIAO Zheng, YANG Xufei   

  1. Beijing Key Laboratory of Multi-phase Flow and Heat Transfer of Low-Grade Energy, North China Electric Power University, Beijing 102206, China
  • Received:2014-04-17 Revised:2014-09-24 Online:2014-12-05 Published:2014-12-05
  • Supported by:

    supported by the National Basic Research Program of China (2011CB710703) and the National Natural Science Foundation of China (51306048).

窄点温差及工质物性对跨临界有机朗肯循环性能的影响

于超, 徐进良, 苗政, 杨绪飞   

  1. 华北电力大学低品位能源多相流与传热北京市重点实验室, 北京 102206
  • 通讯作者: 徐进良
  • 基金资助:

    国家重点基础研究发展计划项目(2011CB710703);国家自然科学基金青年基金项目(51306048).

Abstract: Thermal performance values of 41 working fluids in a trans-critical organic Rankine cycle (ORC) driven by waste heat flue gas of 473.15 K were calculated by means of a theoretical model in which the inlet and outlet temperatures of flue gas were fixed and therefore the thermal efficiency and net work output were unified into one parameter as long as the heat absorbed was given. The influences of pinch point temperature difference (PPTD) in the evaporator and working fluid properties on cycle performance were analyzed. Calculation results showed that for fluids with critical temperature Tc<Tgas,out, and fluids with Tc>0.88Tgas,in, Tc had dominant influence on thermal efficiency. For fluids with Tc between Tgas,out and 0.88Tgas,in, fluid dryness had significant influence on cycle performance, and wet fluids outperformed dry fluids apparently. Wet fluids with Tc between Tgas,out and 0.88Tgas,in exhibited the highest thermal efficiency. For fluids with Tc>0.88Tgas,in, PPTD might lie either inside the evaporator or at the outlet. Thermal performance values of the cycle with PPTD inside the evaporator outperformed that with PPTD at the outlet. Application of such conclusions was confirmed through sensitivity analysis for flue gas inlet and outlet temperatures.

Key words: organic Rankine cycle, trans-critical cycle, critical temperature, pinch point temperature, thermal dynamic, thermal process, thermal property

摘要: 利用约束热源入口及出口温度的热力学模型,将循环热效率及净输出功统一为一个参数,计算41种工质在473.15K废热烟气驱动的跨临界有机朗肯循环中的热力学表现,分析蒸发器内窄点温差及工质物性对循环性能的影响.结果表明,临界温度低于烟气出口温度的工质,及高于0.88倍烟气入口温度的工质,临界温度是循环效率的主要影响因素;临界温度在上述范围之间的工质,干湿性对循环效率影响显著,湿工质效率明显高于干工质.所有循环中,该临界温度范围内的湿工质热效率最高.临界温度高于0.88倍烟气入口温度的工质,窄点温差可能出现在蒸发过程中或蒸发器出口,从热力性能角度看,窄点出现在蒸发过程中的循环明显优于窄点出现在蒸发器出口的循环.改变热源入口及出口温度不会影响上述结论.

关键词: 有机朗肯循环, 跨临界循环, 临界温度, 窄点温差, 热力学, 热力学过程, 热力学性质

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