基于分段法的同轴套管换热器解析模型研究

ANALYTICAL MODEL OF COAXIAL BOREHOLE HEAT EXCHANGER BASED ON SEGMENTATION METHOD

为方便同轴套管换热器的优化设计,提出一种基于分段法的同轴套管换热器解析模型。在解析模型中,根据“热阻理论”和“线热源理论”分别构建钻孔内与钻孔外换热模型,并基于“分段法”和“时间迭加理论”组合构建准三维同轴套管换热器瞬态解析模型。将解析模型计算结果与试验结果、数值分析结果进行对比,验证解析模型的合理性。采用解析模型,研究土体导热系数非均匀分布对同轴套管换热效果的影响,结果表明:“均匀化”土体导热系数的同轴套管换热效率高于“梯度化”土体导热系数的同轴套管,且这种影响随单位深度上土体导热系数变化幅值的增加而增大;在同轴套管换热效率评估过程中应重视土体导热系数的非均匀特性。

In order to optimize the design of Coaxial Borehole Heat Exchanger(CBHE),based on the segmentation method,an analytical model of the CBHE was proposed.In the analytical model,according to the"thermal resistance theory"and"line-source theory",the internal and external heat transfer models of the borehole were constructed respectively,and the 3D CBHE analytical model was constructed based on the"segmentation method"and"time superposition theory".The calculation results of the analytical model were compared with the numerical analysis results and test resnlts,which verified the rationality of the analytical model.Based on the analytical model,the influence of the non-uniform distribution of soil thermal conductivity on the heat transfer effect of CBHE is studied.The results show that the heat transfer efficiency for soil with homogenization thermal conductivity is higher than that of soil with gradient thermal conductivity,and this tendency increases with the increase of the thermal conductivity change amplitude;which means that the non-uniformity of soil thermal conductivity should be considered when evaluating the heat transfer efficiency of CBHE.