套管式和双U型换热器换热性能对比

地埋管换热器广泛应用于各种建筑供暖系统中，提高地埋管换热器的传热效率一直是研究人员关注的热点问题。本文分别在第四系和基岩地层开展了套管式和双 U 型地埋管换热器岩土热响应对比试验。结果表明，套管式换热器增加了循环流体进口流量以及外管壁与岩土体之间的接触面积和热传导能力，换热性能要优于双U型换热器。第四系松散沉积物中，套管式换热器夏季延米换热量约是双Ｕ型的1.76倍。基岩地层条件下，套管式换热器夏季延米换热量约是双Ｕ型的1.37~1.41倍。基岩地层热导率高于第四系松散沉积物，套管式和双U型换热器的换热性能均比第四系地埋管换热器强。研究工作将为地埋管地源热泵系统中套管式换热器的设计及应用提供参考。

Comparison of Heat Transfer Performance between Coaxial Borehole Heat Exchanger and Double U Heat Exchanger

Buried tube heat exchanger is widely used in various building heating systems. Improving the heat transfer efficiency of buried tube heat exchanger has always been a hot issue for researchers. In this paper, rock-soil thermal response tests of coaxial borehole heat exchanger and double U heat exchanger were carried out in quaternary and bedrock strata respectively. The results show that coaxial borehole heat exchanger increases the inlet flow of the circulating fluid, the contact area and the heat conduction capacity between the outer pipe wall and the rock-soil, so the heat transfer performance is better than double U heat exchanger. In the quaternary loose sediments, the heat exchange per meter of the coaxial borehole heat exchanger is about 1.76 times that of the double U heat exchanger in summer. Under the conditions of bedrock strata, the heat transfer per meter of the coaxial borehole heat exchanger is about 1.37~1.41 times that of the double U heat exchanger. The thermal conductivity of bedrock is higher than that of quaternary loose sediments and the heat transfer performance of coaxial borehole heat exchanger and double U heat exchanger is also stronger. The research work will provide reference for the design and application of coaxial borehole heat exchanger in ground source heat pump system.