不同排列方式下多孔套管式换热器传热分析

Heat Transfer Analysis of Multi-borehole Double-pipe Heat Exchangers in Different Arrangement Methods

中深层套管式换热器由于占地面积小、取热量高等优点被广泛使用。描述了中深层套管式换热器的结构特点与工作原理,建立了单孔、双孔及四孔地埋管换热器的传热模型,揭示了多孔地埋管传热研究中叠加降维方法的应用,基于相应的工程项目分析了模拟数据的变化情况。当多孔地埋管以对称方式分布时,对比了单孔、双孔和四孔之间取热量的变化,并分析比较了各自的钻孔间距、大地热流、循环液流量、岩土导热系数、回填材料导热系数及内管导热系数对套管式换热器名义取热量的影响和不同间距对进出口温度的影响。此外,对比了四孔非对称分布时不同排列方式对名义取热量的影响以及进出口水温的变化。其研究结果为多孔中深层地埋管换热器的工程项目提供理论依据和技术指导,进一步促进中深层地热能的推广应用。

The medium-deep double-pipe heat exchangers are widely used because of the advantages of both covering small area and extracting high heat.The structure characteristics and working principle of medium-deep double-pipe heat exchanger are described;the heat transfer models are established for single borehole,double boreholes and four boreholes heat exchanger,revealing the dimension reduction algorithm of superposition principle for the multi-borehole heat exchangers,and analyzing the changes of the simulated data based on the corresponding engineering projects.With regard to single borehole,double boreholes and four boreholes,the heat extractions and other parameters are compared when the multi-borehole heat exchangers are distributed symmetrically;the influences of borehole spacing,geothermal flow,circulating fluid flow,rock and soil thermal conductivity,backfill material thermal conductivity and inner pipe's thermal conductivity on the nominal heat extraction are investigated and compared,and then the influence of different spacing on both inlet and outlet temperatures are discussed.In addition,four boreholes are employed when asymmetrical distribution is set,the influence of different arrangement on the nominal heat extraction and both inlet and outlet water temperatures are compared.Accordingly,the research results can provide theoretical basis and technical guidance for the engineering project of multi-borehole double-pipe heat exchangers,and therefore promote the popularization and application of mdium-deep geothermal energy.