相变回填材料地埋管的传热特性与运行分析

Numerical Simulation of Ground Source Heat Pump with Phase Change Backfills Materials

在所建立的三维非稳态数值模型上,定量分析了传统回填土和相变回填材料地埋管系统的换热特性、间歇运行工况、相变恢复过程以及周围土壤温升情况。通过液相分数的变化趋势与变化云图,探讨了相变过程对地埋管系统换热规律的影响。研究表明相变回填材料可以有效地减缓钻井内热量堆积对埋管周围土壤的热影响幅度,有利于系统的长期稳定运行。在传统的间歇运行模式下,相变回填材料能够得到较好的恢复,为下一个周期的运行提前蓄能。且PCM地埋管系统不能通过提高管内流体流速来增强换热,换热效率最高时流速为0.3 m/s。

Based on the established three-dimensional unsteady-state numerical model,the heat transfer characteristics,intermittent operation conditions,phase change recovery process and soil temperature rise around the traditional backfill and phase change backfill material buried pipe system were analyzed quantitatively.The influence of phase change process on heat transfer law of buried pipe system was discussed by the variation trend and cloud diagram of liquid fraction.The study shows that PCM can effectively alleviate the heat effect of heat accumulation in drilling on the soil around buried pipe.That is conducive to the long-term stable operation of the system.Under the traditional intermittent operation mode,the same backfilling material can be restored well,so that the energy can be stored in advance for the next cycle.In addition,the PCM buried pipe system cannot enhance the heat transfer by increasing the flow rate in the pipe when the maximum flow rate reaches 0.3 m/s.