基于正交试验的中深层U型地埋管换热器换热性能影响因素分析

Numerical Simulation Analysis of Factors Affecting Heat Transfer Performance of Deep U-Bend Pipe Heat Exchanger

对中深层U型地埋管换热器换热性能影响因素进行了研究,建立了中深层U型地埋管换热器三维全尺寸数值传热模型,通过正交试验极差法,分析了入口温度、岩土热导率、地温梯度、埋深以及支管间距的影响。结果表明,这5项因素对中深层U型地埋管换热器换热性能的影响显著性依次为:埋深、地温梯度、入口温度、岩土热导率、支管间距。埋深、地温梯度对换热性能的影响近似于线性;岩土热导率对换热性能的影响则接近于抛物线变化,随岩土热导率的增加,换热性能快速提升;当入口温度从15℃升高至20℃时,平均进出口温差迅速下降,换热量迅速减少,因此建议U型地埋管的入口温度应小于20℃。

The influencing factors of heat transfer performance of U-shaped buried pipe heat exchanger in middle and deep layers are studied.A three-dimensional full-scale numerical heat transfer model of U-shaped buried pipe heat exchanger in middle and deep layers is established.The influences of inlet temperature,geotechnical thermal conductivity,geothermal gradient,buried depth and branch pipe spacing are analyzed by orthogonal test range method.The results show that the significant effects of these five factors on the heat transfer performance of U-shaped buried pipe heat exchanger in the middle and deep layers are as follows:buried depth,geothermal gradient,inlet temperature,geotechnical thermal conductivity,and branch pipe spacing.The effects of burial depth and geothermal gradient on heat transfer performance are approximately linear.The influence of soil and soil thermal conductivity on heat transfer performance is close to a parabolic variation.With the increase of thermal conductivity,the heat transfer performance increases rapidly.When the inlet temperature rises from 15℃to 20℃,the average temperature difference between inlet and outlet decreases rapidly and the heat transfer decreases rapidly.Therefore,it is suggested that the inlet temperature of U-shaped buried pipe should be less than 20℃.