基于实际工程的地埋管地源热泵回填材料导热性能差异分析

Differential Analysis of Thermal Conductivity of Ground-source Heat Pump Backfill Material of Underground Pipe Based on Actual Engineering

为研究实际工程应用中回填材料导热性能差异,以郑州市浅层地热能示范工程为研究对象,通过现场热响应试验、地温监测、数值模拟对中细砂、中细砂+水泥、中细砂+膨润土、原浆四种常见回填材料导热性能进行分析.研究结果表明:原浆的平均导热率最低为1.83 W/(m·℃),中细砂的平均导热率最大为2.17 W/(m·℃);同时中细砂排热和取热下单位深度换热量也为最大,分别为48.52 W/m和47.38 W/m.夏季制冷时中细砂+水泥材料温度仅升高0.0002℃,远低于中细砂材料温度升高;而冬季供暖时,四种材料的温度下降值相近,最小为4.2842℃.基于数值模拟结果,中细砂放热和吸热工况下热影响半径最小,为分别5.5 m和6 m;同时,岩土体温度增温速度由大到小为中细砂、原浆、中细砂+膨润土、中细砂+水泥.因此,中细砂导热性能最好,可作为研究区域地埋管地源热泵回填材料的首选.研究成果为场地条件相似地区地埋管地源热泵回填材料选择提供依据,并对推进郑州地区能源绿色低碳发展具有一定参考意义.

To investigate the differences in thermal conductivity of backfill materials in actual engineering applications,the shallow geothermal energy demonstration project in Zhengzhou City was selected as the research site.The thermal conductivity of four common backfill materials(medium-fine sand,medium-fine sand mixed with cement,mediumfine sand mixed with bentonite,and slurry)was analyzed using on-site thermal response tests,ground temperature monitoring,and numerical simulation.The results showed that the average thermal conductivity of raw slurry was the lowest at 1.83 W(/m·℃),whereas medium-fine sand exhibited the highest average thermal conductivity at 2.17 W(/m·℃).Additionally,the heat exchange per unit depth for heat dissipation and extraction in medium-fine sand was the highest,measuring 48.52 W/m and 47.38 W/m,respectively.The temperature rise of the medium-fine sand mixed with cement material during summer cooling was only 0.0002℃,significantly lower than that of the medium-fine sand material.Similarly,during winter heating,the temperature decrease of the four materials was similar,with a minimum temperature of 4.2842℃.Based on numerical simulation results,the radius of pore thermal influence under exothermic and heat absorption conditions is smallest for medium-fine sand,measuring 5.5 m and 6 m,respectively.Moreover,the rate of temperature increases in the geotechnical body decreased in the following order:medium-fine sand,raw slurry,medium-fine sand mixed with bentonite,and medium-fine sand mixed with cement.Therefore,with its superior thermal conductivity,medium-fine sand is recommended as the primary choice for backfill material for ground source heat pumps in buried pipe installations within the study area.The research results provide a basis for selecting backfill materials for ground source heat pumps in buried pipe installations under similar site conditions.Furthermore,they have significant implications for promoting green and low-carbon energy development in Zhengzhou.