变温热源Lenoir循环功率和效率优化

Power and Efficiency Optimizations of a Variable-Temperature Heat Reservoir Lenoir Cycle

应用有限时间热力学理论,建立了内可逆变温热源定常流Lenoir热机模型,导出了其功率P和热效率η。通过数值计算,得到了P和η与换热器的热导率分配u_(L)和工质与热源间的热容率匹配C_(wf1)/C_(H)之间的关系。结果表明:当高温侧换热器热导率U_(H)、低温侧换热器热导率u_(L)给定时,P-η为一个“点”;当u_(L)可优化时,P-u_(L)和η-u_(L)呈类抛物线型变化,即存在热导率分配最优值u L P(opt)、u L_(η(opt)),使循环达到最大功率点P_(max)和最大效率点ηmax;随着C_(wf1)/C_(H)的增大,P_(max)-C_(wf1)/C_(H)呈类抛物线型变化,即存在热容率匹配最优值C_(wf1)/C_(H)_(opt),使循环达到二次功率最大值(P_(max))_(max)。

Applying finite-time thermodynamics theory,an endoreversible steady flow Lenoir cycle model with variable-temperature heat reservoirs is established,and the expressions of power P and thermal efficiencyηare derived.By numerical calculations,the characteristic relationship between P,ηand the heat conductance distribution u_(L)of the heat exchangers,and the relationship between P,ηand the thermal capacity rate matching C_(wf1)/C_(H)of working fluid and heat source are studied.The results show that when the heat conductances of the hot-side and cold-side heat exchangers U_(H),u_(L)are constant,P-ηis a certain"point".When u_(L)can be optimized,P-u_(L)andη-u_(L)show parabolic-like change,which means there exist optimal values of heat conductance distributions u_(L P(opt)),u L_(η(opt))to make the cycle reach the maximum power point P_(max)and the maximum efficiency pointηmax.With the increase of C_(wf1)/C_(H),P_(max)-C_(wf1)/C_(H)shows a parabolic-like change,which indicates there exists an optimal value of thermal capacity rate matching(C_(wf1)/C_(H))opt to make the cycle reach the double-maximum power point(P_(max))_(max).