中深层套管式地埋管换热器取热性能研究及经济性分析

The paper, FLUENT software is used to establish a three-dimensional numerical heat transfer model of deep coaxial borehole heat exchanger, and based on the orthogonal test range method, the effects of inlet temperature, buried depth, inner diameter, geotechnical thermal conductivity and geothermal gradient on the heat transfer performance of deep borehole heat exchanger are analyzed. The results show that the significant effects of these five factors on the heat transfer performance of deep coaxial borehole heat exchanger are as follows: buried depth, geothermal gradient, inlet temperature, geotechnical thermal conductivity and inner diameter. Then, based on the average energy cost method, the economic evaluation method for deep coaxial borehole heat exchanger is established. It is found that the average energy cost decreases first and then increases with the increment of buried depth. With the given parameters in this paper, the deep coaxial borehole heat exchanger with 2 500 m buried depth has the lowest average energy cost and the best economy. The methods and conclusions can provide reference for the optimization research and engineering application of the deep coaxial borehole heat exchanger.