竖直串联地埋管蓄热的传热分析

为解决大温差地下蓄热的传热分析及其工程应用,基于传统的并联地热换热器地下温度场分布,围绕地埋管大温差蓄热的地源热泵复合系统,针对竖直多级串联地埋管蓄热方法,建立了其物理与数学模型,进行了多级串联地埋管换热器传热分析,得了适宜工程应用的三级串联地埋管换热器目标函数的最优解.结果表明：三级串联地埋管换热器逐级换热量比的最优解为β1 =0.357800、β2 =0.332749、β3=0.309451;定期改变循环液流动方向,能够使各级地埋管换热效率趋于均匀,提高串联地埋管换热器的总换热强度;大温差蓄热应考虑地埋管换热器的承受能力,一般PE管材换热器承受温度不宜超过80℃.

Thermal investigation of in-series vertical ground heat exchangers for seasonal heat storage

A novel borehole configuration of multistage-series circuits is proposed to not only satisfy the requirement of the large temperature drop by the industrial process but also provide a supplemental heat source for conventional ground coupled heat pump systems which have a serious cold accumulation during a year.Based on the heat transfer model of conventional ground heat exchanger （GHE）,a mathematical simulation model of multistage series circuits is developed to illustrate the heat transfer process of the underground thermal storage.The optimum recharging heat fractions for the three-level series circuits,which are suitable for the engineering application,are simulated and discussed by means of the heat transfer model.The results demonstrate：the optimum objective functions of recharging heat fraction for each circuit are β1 =0.357800,β2 =0.332749,β3 =0.309451; In order to equilibrate the ground temperature for multistage circuits,it is recommended to reverse the flow direction at regular time intervals to enhance the total heat transfer efficiency of the GHE system; further studies should be conducted on the pipe material which is suitable for the thermal storage with high temperature as the PE pipes currently used cannot withstand higher temperatures,such as over 80℃.