Influence of spacing between heat pipe exchangers on the thermal storage and release performance of phase change backfill body
In order to efficiently utilize the geothermal resources of high-temperature mines and solve the impact of high-temperature environment on the mining process,a three-dimensional unsteady heat transfer numerical model of the heat pipe-phase change backfill body mine geothermal mining system was established.The influences of the arrangement spacing between the heat pipe heat exchanger and the surrounding rock on system temperature distribution,liquid fraction of phase change material,circu-lating cooling water temperature,and heat storage capacity and heat release capacity of system were studied.The results indicate that the closer the heat pipe is to the surrounding rock,the faster the melt-ing of PCM is during the heat storage stage,and the slower the solidification of PCM is during the coex-istence stage of heat storage and release.The outlet temperature and inlet-outlet temperature difference of the circulating cooling water at heat pipe condensation section will increase with the decrease in the distance between heat pipe and surrounding rock.As the spacing between heat pipe and surrounding rock decreases from 95 mm to 20 mm,the inlet-outlet temperature difference of cooling water during the stable operation process increases from 2.50 K to 4.97 K.During the heat storage stage,the system heat storage capacity first increases gradually and then remains constant over time.During the coexis-tence stage of heat storage and release,the system heat release continues to grow at a rate which gradu-ally decreases first and then remains constant.When the layout distance between heat pipe and sur-rounding rock decreases from 95 mm to 20 mm,the system total heat storage capacity increases by 72.89%,the heat release capacity increases by 91.10%,and the system energy efficiency coefficient increases from 81.71%to 90.32%.The research results can provide theoretical basis and technical guidance for the efficient exploitation and utilization of geothermal energy in mines using the heat pipe phase change material coupling system.
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