热力系统整体分析和优化的热量流法

Heat current method for integrated analysis and optimization of thermodynamic systems

热力系统的性能优化对提高能源利用效率具有重要意义,但传统分析方法难以满足复杂系统高效分析的需求.近年来基于理论发展的热量流法及相应的求解算法为热力系统的分析与优化提供了一种新的解决方案.本文首先介绍热力系统热量流模型的规范化构建方法,并以余热回收朗肯循环为例说明了模型构建的具体流程.随后,结合系统中工质的流动约束及物性,提出了热力系统整体数学模型的规范化构建方法,能够分离系统约束中线性、非线性显式和非线性隐式约束,最少化需要迭代求解约束的数量.利用上述约束分离特性提出了热力系统整体数学模型的分层-分治求解算法,能够大幅降低计算复杂度,并显著提高计算鲁棒性.最后,以三压蒸汽发电系统为例,阐明了热量流模型及分层-分治算法与传统求解方法相比在求解时间、所需初值数量等方面的优势.

Performance analysis and optimization of thermodynamic systems are important in increasing the efficiency of energy systems, but traditional approaches cannot meet the demand of high-efficiency performance analysis for complex thermodynamic systems. Based on the entransy theory, the recently developed heat current method, combined with the specialized simulation algorithm, offers a new and attractive solution for performance analysis of thermodynamic systems. This paper first presents the standardized heat current modeling strategy for thermodynamic systems, taking a Rankine cycle power generation system as an example to present the modeling procedure. Combining flow constraints and physical property constraints of working fluids, the framework of construction of a global system mathematical model is then presented. In the proposed framework, linear, nonlinear explicit, and nonlinear implicit system constraints can be separated. Consequently, the number of constraints needing to be solved iteratively is minimized. Based on this separation feature, this paper further proposes and presents a hierarchical and categorized algorithm that could reduce calculation time greatly and improve calculation stability significantly. Finally, a triple-pressure steam power generation system is investigated to demonstrate the advantages of the proposed hierarchical and categorized algorithm compared with conventional methods from the aspects of the time required for calculation and the initial values required.