3D dynamic numerical programming and calculation of vertical buried tube heat exchanger performance of ground-source heat pumps under coupled heat transfer inside and outside of tube

Targeting the underground vertical buried tube heat exchangers (BTHEs) of ground-source heat pumps, a physicomathematical model of heat and mass transfer that couples the turbulent flow field in the tube with the groundwater seepage in the surrounding soil was established in this study. FORTRAN language was used to design a 3D dynamic numerical calculation program for this model, and the geotechnical thermal response test data was used to verify the reliability of this program. It also used the program to comparatively analyze the error influence of the assumption of uniform velocity flow field in the tube on heat transfer performance analysis. Considering the turbulent flow field in the tube, the influence of groundwater seepage and inlet flow velocity in buried tube on the heat transfer performance of BTHEs was further explored. The results show that the assumption of uniform velocity flow field in the tube caused a relatively significant error with the heat transfer performance analysis on buried tube, and both the soil seepage velocity and flow velocity in the tube influenced the heat transfer performance of buried tube. This study aimed to provide a programming method for the in-depth study of buried tube heat transfer performance.