单井U型地埋管换热器传热特性与热渗耦合特性分析

Analysis of heat transfer characteristics and thermal-permeability coupling characteristics of single U-tube borehole heat exchangers

在“双碳”目标下,浅层地热能供暖(冷)作为一种新型的清洁能源利用形式得到广泛使用。为提高浅层地热能的利用效率,以我国北方某综合能源供暖(冷)项目土壤源热泵系统为研究对象,构建单井U型地埋管换热器的三维非稳态传热模型,并利用Fluent软件分析其传热特性与热渗耦合特性。选取4.0,4.5,5.0 m等3个不同埋管间距和106.0,113.0,120.0 m等3种不同埋管深度,对地埋管换热器的换热总量及单位井深换热量分别进行对比分析。分析结果表明,埋管间距为4.0 m、埋管深度为106.0 m时,单井地埋管换热器的换热效果最佳。对无渗流和有渗流及不同渗流速度下地埋管换热器温度场进行对比分析,结果表明,地下水渗流会对地埋管换热器换热效率带来正向影响,并且随着渗流速度的增加,换热效果更好。上述分析为实际工程的地埋管方案设计提供参考依据。

To achieve the"dual carbon"target,shallow geothermal energy heating(cooling),a new utilization form of clean energy,has been widely applied.To improve the efficiency of geothermal energy,taking the ground source heat pump of an integrated energy heating(cooling)system in northern China as the research object,a 3D unsteady-state heat transfer model of a single U-tube borehole heat exchanger(BHE)was constructed,and its heat transfer characteristics and coupling characteristics thermal conduction and groundwater seepage were analyzed by the software Fluent.Comparative analyses on the total transfer heat and transfer heat per unit length were made on the BHE with three different spacing distances(4.0,4.5 and 5.0 m)and three different tube lengths(106.0,113.0 and 120.0 m),respectively.The analysis results show that the BHE with 4.0 m spacing distance and 106.0 m tube length demonstrates the optimal performance.Comparing the temperature fields of the BHE with and without seepage flow,the results show that seepage flow exerts positive effect on the BHE heat transfer efficiency,and the faster the seepage flows,the higher the heat transfer efficiency is.The analyses above provide references for the design of practical examples of BHE projects.