为了探讨土壤源热泵地下埋管传热强化及其控制的有效措施,基于相似理论搭建了垂直U型地下埋管换热模型试验台,进行了不同回填材料、不同间歇运行控制模式及不同进口温度对埋管周围土壤温度场及换热性能影响的试验测试；建立了垂直U型埋管准三维非稳态数值传热模型,分析了间歇运行与进口温度对土壤温度分布与埋管换热性能的影响.研究结果表明:导热性能好的回填材料能有效提高地埋管的换热能力,但考虑到两支管间热短路的增加,回填材料导热系数并非越大越好.同时,埋管换热量随运停时间比的减小和进口温度的增加而增大；此外,垂直地埋管可利用传热温差上层高于下层,因此,地埋管换热主要集中在中上层土壤.试验验证表明,所建数值模型能较好地模拟地下换热过程,其预测精度在5％以内.%In order to investigate the effective measures of heat transfer enhancement of ground heat exchanger(GHE) and its operation control used in ground coupled heat pump(GCHP) , a model experimental apparatus for the heat transfer performance test of GHE was set up based on similarity theory. The influences of different backfill materials, different intermittent operation modes and different inlet fluid temperatures on the heat transfer performance of GHE and its surrounding soil temperature field were tested based on the experimental apparatus. A quasi three-dimensional heat transfer model was developed for the vertical U-bend GHE. The effects of intermittent operation mode and inlet fluid temperatures on the heat transfer performance of GHE and its surrounding soil temperature distribution were also analyzed based on the model. The results indicate that a backfill with high thermal conductivity can improve the thermal performance of U-tube GHE, but the thermal conductivity should not be increased unlimitely considering the thermal interference of two adjacent legs of U-tube. At the same time, the heat exchange rate of GHE will increase with the decrease of the ratio of on-time to off-time and the increase of inlet temperature. Additionally, the heat transfer temperature difference between the fluid and surrounding soil at the up-layer is usually larger than that at the down-layer, and thus the heat transfer at the upper part is predominate in the borehole. The experimental validations show that the developed mathematical model can be used to simulate effectively the heat transfer of vertical U-tube GHE, and the predicted error is less than 5%.
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