基于“分子特征-工质物性-循环评价”耦合建模机制的ORC热力学研究

Organic Rankine cycle (ORC) is one of the effective technical approaches to achieve the efficient utilization of medium and low temperature heat energy. As the foundation of all thermal power cycles, the thermophysical properties of the working fluid have an important influence on the ORC. This project aims to solve the research separation between the thermophysical properties of working fluid and the evaluation of ORC performance. In this project, a scientific conception, the coupling mechanism of molecular characteristic, thermophysical properties and cycle evaluation, is proposed, to provide theoretical guidance for the active design of the working fluid on the molecular structure level which aims at the optimization of the thermodynamic performances of ORC. By building the ORC thermodynamic model which couples the universal equation of state, the influence of sensitivity of thermophysical constants is clarified. The quantitative structure activity relationship is used to reveal the correlation mechanism between the molecular structure characteristics of the working fluid and its macroscopic thermophysical properties, and to obtain the coupled modeling mechanism for the bottom-up three-stage process, that is, from the molecular characteristics, thermophysical properties to cycle evaluation. Finally, the factors that affect the actual efficiency limit of ORC and the energy loss mechanism of each key component are clarified at the molecular structure level. The research work involved in this project can provide new ideas for improving the heat–to–power efficiency of ORC.

有机朗肯循环（ORC）是实现中低温热能高效利用的有效技术途径之一。而工质作为一切热力循环构建的基础，其热物理性质对ORC有着重要影响。本项目致力于解决当前工质热物理性质和ORC循环评价分立研究的现状，提出“分子特征-工质物性-循环评价”耦合建模机制的科学构想，以期实现对ORC热力学性能优化为导向的工质分子结构层面的主动设计提供理论指导。通过构建耦合通用型工质状态方程的ORC热力学模型，阐明现有工质体系中物性常数敏感性的影响规律；采用定量构效关系方法，揭示由工质分子结构特征到其宏观热物理性质的关联机理；获得由分子特征、工质物性到循环评价自下而上的三阶递进且相互耦合的建模机制；最终在工质分子结构层面阐明ORC实际效率极限的影响因素及各关键部件的能量损失机理。通过本项目的研究，可以为提高ORC的热功转换效率提供新思路。

有机朗肯循环（ORC）是中低温热能高效热功转换研究的理想载体循环，在余热回收、可再生能源利用等领域具有较大的应用潜力。本项目针对当前工质热物理性质和ORC性能评价分立研究的现状，提出了“分子特征-工质物性-循环评价”耦合建模机制的科学构想，构建了耦合通用型工质状态方程的ORC热力学模型；采用定量构效关系方法，揭示了由工质分子结构特征到其宏观热物理性质的关联机理；获得了由分子特征、工质物性到循环评价自下而上的三阶递进且相互耦合的建模机制；探究了现有工质体系下相较于卡诺循环效率更具有指导意义的ORC热力学性能极限研究方法，阐明了临界性质、偏心因子和定压比热等工质特征参数对ORC实际效率极限的影响规律及各关键部件的能量损失机理。基于本项目的研究成果，可以为面向中低温热能高效利用的热力循环工质优选及主动设计提供理论支撑。