竖直单U型地埋管传热模拟分析

Simulation Analysis on Heat Transfer of Vertical Single U-pipe Ground Heat Exchanger

针对地源热泵系统中的竖直单U型换热器的传热问题,利用FLUENT软件对其传热特性进行了稳态数值模拟。计算了管内流速,回填物导热系数,支管间距等因素对竖直单U型地埋管换热器换热性能的影响。通过数值模拟发现,管内流速过小时,地埋管换热器会出现严重的热短路现象。对比分析得出管内最佳流速为0.6 m/s～0.8 m/s;进回水支管间距越大,地埋管换热器换热性能越好;回填物的导热系数是影响地埋管换热器换热性能的一个重要因素,其最佳值与管内流速和管间距有关。综合考虑上述3个因素对地埋管换热器换热性能的影响,得出了支管间距为86 mm,管内流速为0.6 m/s～0.8 m/s,回填物导热系数为土壤导热系数的1～2倍时,竖直单U型地埋管的换热性能最好的结论。

Aiming at the heat transfer problem of vertical single U-pipe ground heat exchanger in ground source heat pump system, the numerical simulation of steady heat transfer performance is carried out by using FLUENT software. The influence of flow velocity in the tube, thermal conductivity of backfill and branch spacing on the heat transfer performance of vertical single U-pipe ground heat exchanger is calculated. Through numerical simulation, it is found that there will be a serious thermal short circuit phenomenon in the tube when the velocity is too small, and the best velocity in the tube is 0.6-0.8m/s; The greater the distance between the inlet and outlet branch pipe, the better the heat transfer performance of the buried pipe heat exchanger; And the thermal conductivity of the backfill is an important factor affecting the heat transfer performance of the buried pipe heat exchanger, and the best value is related to the velocity and spacing of pipes. Considering the influence of the above three factors on the heat transfer performance of the buried tube heat exchanger, the conclusion is that the heat transfer performance of the vertical single U-pipe ground heat exchanger is best when the distance of the branch pipe is 86mm, the flow velocity in the tube is 0.6-0.8m/s and the thermal conductivity of the backfill is 1-2 times of the soil thermal conductivity.