Heat transfer performance of buried extremely long ground-coupled heat exchangers with concentric pipes

This study focuses on the heat transfer between the vertical concentric tubes buried underground and the medium-deep rock-soil geothermal energy. The numerical simulation based on an in-house FORTRAN computation program was performed to analyze the mechanism of heat exchange underground. The program was shown to predict the test results of outlet water temperature and heat gain very well under the corresponding operating conditions when engineering data of an actual geothermal well were obtained to validate the numerical scheme. The effects of inlet water temperature and flow rate on the heat exchanger performance were also analyzed in detail. The comparison indicated that the present numerical scheme is able to predict the heat transfer performance of extremely long ground-coupled heat exchanger subject to various geothermal conditions.