变温热源内可逆Braysson循环性能分析与优化

Analysis and Optimization for Performance of Endoreversible Braysson Cycle with Heat Reservoirs of Variable Temperature

用有限时间热力学理论建立了变温热源内可逆Braysson循环模型,导出了功率和效率的数学表达式,分析了循环参数对二者的影响,并通过优化热导率分配和热容率匹配来进一步优化循环功率和效率。结果表明:优化高、低温侧换热器热导率分配过程中,存在一个最佳工质对数温比,使得效率达到最大值;存在一组最佳热导率分配和最佳工质对数温比,使得功率和效率达到双重最大值;优化工质与热源间热容率匹配过程中,存在一组最佳热容率匹配、最佳工质对数温比和最佳热导率分配,使得功率达到三重最大值。因此通过同时优化热导率分配和热容率匹配得到的循环性能更接近实际情况,且此时循环功率存在三重最大值。研究成果可为Braysson循环的相关研究提供一定的参考。

By applying the finite-time thermodynamic theory,an endoreversible Braysson cycle model with heat reservoirs of variable temperature was established,and the expressions of power output and efficiency were derived.The influences of cycle parameters on power and efficiency were analyzed,and optimization of the two were carried out by searching the optimal heat conductance distribution and heat capacity rate match.The results showed that during optimizing the heat conductance distribution,there was an optimal logarithmic temperature ratio of working fluid,which resulted in the maximum value of efficiency,and there was a set of optimal heat conductance distribution and heat conductance distribution,which could make the power and efficiency reach double-maximum.When the heat capacity rate match was optimized,there was a set of optimal heat capacity rate match,logarithmic temperature ratio of working fluid and heat conductance distribution,which could get the triple-maximum value of efficiency.Thus,the cycle efficiency obtained by optimizing heat conductance distribution and heat capacity rate match simultaneously could be in more agreement with actual situation,meanwhile,the cycle efficiency could reach triple-maximun.The research result can provide reference for the related study on Braysson cycle.