竖直双U型地埋管传热特性研究

STUDY ON HEAT TRANSFER CHARACTERISTICS OF VERTICAL DOUBLE U-SHAPED BURIED PIPE

为探究U型地源热泵系统运行过程中土壤温度变化特性,以竖直U型地埋管周围土壤为研究对象,基于有限元分析法建立三维非稳态传热物理模型。研究表明,地埋管周围土壤温度和单位井深换热量均随热泵运行时间增加而增加且趋于稳定;在其他条件不变的情况下双U型地埋管换热量为28.26 W/m,单U型地埋管换热量为26.38 W/m;流体进口流速和土壤温度梯度对单位井深换热量影响很小;流体进口温度和回填材料对土壤温度和单位井深换热量的影响较大;热泵蓄热–恢复和取热–恢复工况下,土壤温度恢复效果随径向距离及恢复时间增加而增加,土壤导热系数越大恢复的程度越接近土壤初始温度值。

In order to investigate the soil temperature variation characteristics during operation of U-type ground source heat pump system,a three-dimensional unsteady heat transfer physical model was established by using the finite element analysis method and taking the soil around the vertical U-type buried pipe as the research object.The results showed that both the soil temperature around the buried pipe and the heat transfer per unit well depth increase with the increase of heat and tend to be stable with the increase of heat pump operating time.When other conditions remain unchanged,the heat transfer of double U-type buried pipe is 28.26W/m,and that of single U-type buried pipe is 26.38W/m.Fluid inlet velocity and soil temperature gradient have little effect on heat transfer per unit well depth.The fluid inlet temperature and backfill material have great influence on soil temperature and heat transfer per well depth.The recovery effect of soil temperature increases with the increase of radial distance and recovery time,and the greater the soil thermal conductivity is,the closer the recovery degree is to the initial soil temperature value.