竖直U形地埋管换热器热短路现象及换热性能研究
Thermal interference and heat transfer performance of vertical U-tube ground heat exchangers
摘要：
针对影响地埋管换热器热短路现象及换热性能的主要因素（回填材料导热系数和热泵运行方式），建立了U形地埋管换热器的三维非稳态数值模型，通过热响应实验验证了该模型。采用FLUENT软件进行模拟分析，得到不同导热系数土壤条件下地埋管换热器的热短路损失系数和每延米换热量随回填材料导热系数的变化规律，推荐采用导热系数比周围土壤稍大的回填材料。对比了地源热泵连续与间歇两种运行方式，得出当回填材料导热系数小于或等于周围土壤导热系数时，间歇运行对热短路现象基本无影响；当回填材料导热系数大于周围土壤导热系数时，间歇运行可使热短路损失系数降低51.6%～74.5%，每延米换热量提高32.6%～34.0%。
Abstract：
For analysing the main factors (thermal conductivity of backfill materials and operating modes of heat pump) affecting thermal interference and heat transfer performance of ground heat exchangers, establishes a three-dimensional unsteady numerical model of U-tube ground heat exchanger, and verifies the model by a thermal response test. Based on the simulation and analysis with FLUENT software, obtains the variation laws of the loss coefficient of thermal interference and heat transfer rate per linear meter with the thermal conductivity of backfill materials on the conditions of the soil with different thermal conductivities, and recommends the backfill material whose thermal conductivity is slightly higher than that of surrounding soil. By comparing the continuous operation mode with the intermittent operation mode, concludes that when the thermal conductivity of backfill materials is less than or equal to that of surrounding soil, intermittent operation has almost no effect on thermal interference. When the thermal conductivity of backfill materials is greater than that of surrounding soil, the loss coefficient of thermal interference could be reduced by 51.6 percent to 74.5 percent, and the heat transfer rate per linear meter could be increased by 32.6 percent to 34.0 percent in intermittent operation mode.
Keywords:ground heat exchanger, backfill material, thermal conductivity, loss coefficient of thermal interference, heat transfer rate per linear meter, intermittent operation, continuous operation