U型埋管换热器及其周围土壤非稳态传热的数值分析

针对地源热泵U型换热器埋管、周围回填材料及土壤传热过程，建立了将U型管壁的边界换热取为第三类对流换热条件的二维非稳态传热模型，并对其温度分布进行了数值模拟分析．分析结果表明：U型埋管换热器管壁内对流换热热阻和管壁导热热阻对U型埋管换热器及其周围土壤非稳态传热过程的影响较小，但相互热干扰造成进、出水管壁自身各角度的温度存在明显差异．各处土壤温度达到准稳定阶段所需要的时间随其与U型埋管的距离增加而增加．

Numerical Analysis of Unsteady Heat Conduction to U-tube Heat Exchangers and Surrounding Soil

A two dimensional transient heat transfer model based on convection boundary condition is established accord- ing to the heat transfer process in the U-tube heat exchanger,backfill material and soil layer ,and numerical analysis of the temperature distribution is also simulated on the base of the established model. Analysis result shows that the convective resistance in the U-tube heat exchanger and the conductive resistance of the U-tube exchanger pipe have a relatively lower inflection to the whole unsteady heat transfer process. The notable temperature difference in the soil layer on the different angles is mainly resulted by the interaction of the two pipes of the under ground heat exchanger,and the time needed to get to steady state is parallel to the distance to the underground heat exchanger.