Working Fluid Distribution and Charge Regulation Control in Organic Rankine Cycle

doi:10.1007/s12204-022-2538-y

Abstract

Abstract: Charge-based studies, in particular investigations of mass distribution, are still almost absent, although the efficiency of the organic Rankine cycle (ORC) has attracted a great deal of scholarly attention. This paper aims to provide a new perspective on the intrinsic relationship among the mass distribution, phase-zone distribution in the heat exchanger (HEX), charge of working fluid (WF), rotation speed of the pump (RSP), and system performance. A comprehensive ORC simulation model is presented by linking each component’s sub-models, including the independent models for HEX, pump, and expander in an object-oriented fashion. The visualization study of mass distribution of the WF in the system is investigated under different working conditions. Furthermore, the volume and mass of the gas phase, two-phase and liquid phase of WF in the HEX and their variation rules are analyzed in-depth. Finally, the strategies of charge reduction considering HEX areas and pipe sizes are investigated. The results show that the model based on the interior-point method provides high levels of accuracy and robustness. The mass ratio of the WF is concentrated in the liquid receiver, especially in the regenerator, which is 32.9% and 21.9% of the total mass, respectively. Furthermore, 2.4 kg (6.9%) WF in the system gradually migrates to the hightemperature side as the RSP increases while 6.1 kg (17.4%) WF migrates to the low-temperature side, especially to the condenser, as the charge in the system increases. Output power and efficiency both decrease gradually after the peak due to changes in RSP and charge. Last, reducing heat transfer areas of the condenser and regenerator is the most effective way to reduce WF charge.

Key words: simulation, organic Rankine cycle (ORC), working fluid charge, mass distribution

摘要： 尽管有机朗肯循环的效率已经引起了大量的学术关注，但基于电荷的研究，特别是对质量分布的研究仍然几乎缺乏。本文旨在对换热器的质量分布、相区分布、工质电荷、泵转速与系统性能之间的内在关系提供一个新的视角。通过以面向对象的方式链接每个组件的子模型，包括换热器、泵和扩展器的独立模型，给出了一个全面的有机朗肯循环仿真模型。对不同工况下系统中工质的质量分布进行了可视化研究。深入分析了换热器中工质气相、两相和液相的体积和质量及其变化规律。最后，研究了考虑换热器面积和管道尺寸的减荷策略。结果表明，基于内点法的模型具有较高的精度和鲁棒性。工质的质量比集中在液筒中，尤其在再生器中，分别占总质量的32.9%和21.9%。此外，随着泵速的增加，系统中的2.4 kg (6.9%) 的工质逐渐向高温侧迁移，而随着系统中电荷的增加，6.1 kg (17.4%) 的工质向低温侧迁移，特别是向冷凝器迁移。由于泵速和电荷的变化，输出功率和效率在峰值后逐渐下降。最后，减小冷凝器和蓄热器的换热面积是减少工质负荷的最有效途径。

关键词: 模拟，有机朗肯循环，工质电荷，质量分布

CLC Number:

YE Zhenhong(叶振鸿), WANG Wei(王炜), LI Xinhua(李新华), CHEN Jiangping(陈江平). Working Fluid Distribution and Charge Regulation Control in Organic Rankine Cycle[J]. J Shanghai Jiaotong Univ Sci, 2024, 29(2): 188-201.

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