竖直埋管地热换热器钻孔内的传热分析

准三维模型为竖直埋管地热换热器的结构优化提供了较为精确的理论基础。利用准三维模型对竖直埋管地热换热器进行分析与研究得出，不同的行程布置对双U型埋管地热换热器的传热性能有较大影响。就钻孔内热阻的对比，双U型埋管比单U型埋管钻孔内的热阻低，因而双U型埋管地热换热器较单U型埋管地热换热器更为合理。

ANALYSIS OF THE HEAT TRANSFER INSIDE A BOREHOLE OF VERTICAL GROUND HEAT EXCHANGERS

The ground source heat pump (GSHP) is interested in all over the world. The GSHP features in its ground heat exchanger (GHE), which is quite different to conventional heat exchangers and contributes to a substantial portion of the initial cost of GSHP systems. As the thermal resistance of GHE has great impact on sizing GHE, it is crucial to determine the thermal resistance with higher accuracy for the cost-effective applications of GSHP. The previous models of GHE, based on numerical methods or over-simplified assumptions, are either inconvenient for the direct applications or inaccurate in practical engineering.A solid theoretical foundation to optimize GHE was provided using the quasi-3-dimensional model, the different circulating layouts of a borehole with two U-tubes have great impact on the performance of the ground heat exchangers. Analysis and calculations showed that the double U-tube vertical GHE was superior to the single U-tube geothermal heat exchanger as thermal resistance in regards, thus the double U-tube vertical geothermal heat exchangers were recommended to the priority choice of GHE in GHSP systems.