基于火积理论的超临界CO2传热特性及系统的热量输运规律研究

For the development and application of supercritical CO2, the comprehensive and efficient heat transfer characteristic analysis of convective heat transfer, the related heat exchanger and heat transfer system is the significant theory basis. However, the thermal property variation of supercritical CO2 increases the difficulty of heat transfer characteristic and heat exchanger performance predicting and the heat transfer system modeling. This project aims at the key issues on account of the supercritical CO2 property variation, such as the integrated influence law, the performance analysis method and the system transportation law. The project studies the entransy dissipation criterion function which characterizes the convective heat transfer characteristics of supercritical CO2, and clarifies the integrated heat transfer influence law with the extremely property variation of supercritical CO2 according to the irreversible analysis. Based on the power flow method combining with the correction factor, the entransy dissipation-based thermal resistance expression of heat exchanger is deduced and the related power flow model is constructed. An iterative algorithm based on classification and stratification is proposed to validate the power flow method for the performance analysis of supercritical CO2 heat exchanger with thermal property variation. Moreover, the typical supercritical CO2 heat transfer system is studied to construct the corresponding power flow model for revealing the thermal property variation and system typological characteristics simultaneously. The analogical Ohm's law of heat transfer system is put forward expounding the whole heat transport law of the system. Finally, the project realizes the overall modeling and analysis of supercritical CO2 heat transfer system.

超临界CO2传热规律和相关换热器及系统换热特性的全面高效分析是发展应用超临界CO2光热技术的重要理论基础，但物性变化特征增加了传热特性、换热器性能分析及换热系统整体建模的难度。本项目针对超临界CO2物性变化“整体影响规律、性能分析方法、系统输运规律”等关键问题，研究表征变物性超临界CO2对流传热特性的火积耗散准则函数，从不可逆角度阐明变化趋势各异的热物性对超临界CO2传热特性的整体影响规律；基于能量流法结合修正因子推导变物性超临界CO2换热器的火积耗散热阻表达式并构建相关的能量流模型，提出分类分层的迭代算法并验证物性变化工况下超临界CO2换热器性能分析的能量流法；研究典型超临界CO2换热系统，构建兼顾物性变化特性和系统拓扑特征的超临界CO2换热系统能量流模型，提出变物性换热系统的“类欧姆定律”，并阐明系统中热量的整体输运规律，实现变物性超临界CO2在系统中的整体建模和分析。

超临界CO2的传热规律和相关换热器及系统换热特性的全面高效分析是发展和应用超临界CO2光热发电技术的重要理论基础。本项目针对超临界CO2物性变化“整体影响规律、性能分析方法、系统输运规律”等关键问题，围绕超临界CO2热系统中“过程-部件-系统”的三个层次，基于火积理论和热量流法，提出了表征超临界CO2传热过程特性的等效火积耗散热阻，以进口温差为热压，结合修正因子提出了换热器的通用热阻模型，并由此构建了超临界CO2换热器及换热系统的热量流模型，实现了物性参数、结构参数和运行参数的一体化分析；针对超临界CO2冷却过程，当进口压力为11~12 MPa时，换热量将达到最大，此时等效火积耗散热阻将达到最小；针对超临界CO2-冷却水的串联换热系统，结合整体热量流模型和遗传算法，优化发现存在最优的管径分布，使得超临界CO2的出口温度达到最低；基于换热器通用热阻模型，结合传热-流动过程的经验关联式，构建了热系统中兼顾过程/部件特性和系统拓扑特征的整体热量流模型及相关的整体传输矩阵约束，并将其应用于换热器结构优化、传热传质耦合、热电耦合、双回路热管理系统及电热综合能源系统的建模和优化中，从而实现了过程-部件-系统耦合的整体分析。