Differences and relations of objectives, constraints, and decision parameters in the optimization of individual heat exchangers and thermal systems  

作　　者：CHEN Qun WANG YiFei 

机构地区：[1]Key Laboratory for Thermal Science and Power Engineering of Ministry of Education, Department of Engineering Mechanics,Tsinghua University

出　　处：《Science China(Technological Sciences)》2016年第7期1071-1079,共9页中国科学（技术科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.51422603,51356001&51321002);the National Basic Research Program of China("973"Project)(Grant No.2013CB228301)

摘　　要：Performance improvement of heat exchangers and the corresponding thermal systems benefits energy conservation, which is a multi-parameters, multi-objectives and multi-levels optimization problem. However, the optimized results of heat exchangers with improper decision parameters or objectives do not contribute and even against thermal system performance improvement. After deducing the inherent overall relations between the decision parameters and designing requirements for a typical heat exchanger network and by applying the Lagrange multiplier method, several different optimization equation sets are derived, the solutions of which offer the optimal decision parameters corresponding to different specific optimization objectives, respectively. Comparison of the optimized results clarifies that it should take the whole system, rather than individual heat exchangers, into account to optimize the fluid heat capacity rates and the heat transfer areas to minimize the total heat transfer area, the total heat capacity rate or the total entropy generation rate, while increasing the heat transfer coefficients of individual heat exchangers with different given heat capacity rates benefits the system performance. Besides, different objectives result in different optimization results due to their different intentions, and thus the optimization objectives should be chosen reasonably based on practical applications, where the inherent overall physical constraints of decision parameters are necessary and essential to be built in advance.

关 键 词：energy conservation thermal system physical constraint decision parameter optimization objectives 

分 类 号：TK172[动力工程及工程热物理—热能工程]