基于田口方法的垂直单U地埋管钻孔热阻优化分析

ANALYSIS AND OPTIMIZATION OF BOREHOLE THERMAL RESISTANCE OF VERTICAL SINGLE U-TUBE GROUND HEAT EXCHANGER USING TAGUCHI METHOD

基于Comsol有限元软件建立垂直地埋管二维导热数值模型,在综合考虑支管半径、钻孔半径、两支管间距、土壤导热系数和回填材料导热系数的基础上进行仿真实验,得出不同热物性参数值下的钻孔热阻并验证模型的可靠性。基于田口方法,建立L27(35)正交表,利用信噪比得出最优热物性参数组合,进而对各参数进行方差分析,得出各参数对钻孔热阻值的关联度及贡献率,最终求解出最优钻孔热阻值。研究结果表明:钻孔半径、回填导热系数和支管半径具有较高的贡献率;最优参数组合为rp=0.020 m,r_(b)=0.06 m,x_(c)=0.07 m,λ_(s)=0.90 W/(m·K),λg=2.00 W/(m·K);优化后的钻孔热阻值较原阻值最大可减少约81.67%,为0.033 m·K/W,埋管深度最大可减少约35.79%,为56.93 m。

In this study,the effects of five parameters including the pipe radius,the borehole radius,the pipe-pipe distance,soil thermal conductivity and grout thermal conductivity on the value of borehole thermal resistance are investigated.A 2D heat conduction numerical model is established using Comsol finite element software and its accuracy is verified.In order to implement the analysis,L27(35)orthogonal array is established and the values of borehole thermal resistance in different parameter combination are obtained.The optimal parameter set are attained by applying the Taguchi method.The optimal parameters combination is shown as follows:rp=0.020 m,r_(b)=0.06 m,x_(c)=0.07 m,λ_(s)=0.90 W/(m·K),λg=2.00 W/(m·K).Results using above optimal parameter set reveals 81.67%decrement in the borehole thermal resistance and 35.79%decrement in the borehole length.The analysis of variance technique is carried out lastly to figure out the relative importance of tested parameters.The pipe radius,grout thermal conductivity and borehole radius play vital roles in optimizing the value of borehole thermal resistance whereas the pipe-pipe distance and soil thermal conductivity’s impact can be nearly neglected.