土壤热渗耦合作用下U型埋管换热器换热特性数值模拟

Numerical simulation of U-type underground heat exchangers under condition of coupled thermal conduction and groundwater seepage

建立了管内流体流动及周围土壤热渗耦合传热的垂直U型地埋管换热数理模型,采用数值方法对有渗流和无渗流工况下的土壤温度场分布、埋管出口温度、不同渗流速度下的单位井深换热量进行了模拟计算分析。结果表明,地下水渗流作用能减小埋管出口升温幅度,在埋管入口平均温度为33℃时,有渗流工况下的埋管出口平均温度为29.91℃,无渗流工况下的埋管出口平均温度为30.85℃。单位井深换热量随渗流速度的增大而增加,当地下水渗流速度为10 m/a和400 m/a时,与无渗流工况相比,单位井深换热量分别增大了约6.33%和71.33%。

A mathematical physical model of vertical U-type underground pipe is established, which considers fluid flowing in the tube and surrounding soil with coupled thermal conduction and ground- water seepage condition,the numerical method is used for simulation. Under a condition with seepage and another condition without seepage, the parameters such as soil temperature field distribution, buried tube＇s outlet temperature, and heat transferred per unit depth of borehole are analyzed and cal- culated respectively. The results show that groundwater seepage can slow down the buried tube^s outlet temperature rise. When the average temperature at the inlet is 33 ℃ ,the average temperature at the outlet with seepage is 29.91 ℃ and is 30.85℃ without seepage. The heat transferred per unit depth of borehole increases along with the increase of seepage velocity. When the flow rate is 10 m/y and 400 m/ y, comparing to no seepage condition, the heat transferred per unit depth of borehole will be increased by about 6.33% and 71.33%.