Attenuation and Restoration Characteristics of Ground Temperature in a U-type Deep-Buried Pipe Heat Transfer System

By examining an engineering site using a U-type deep-buried pipe as a case study, this study explored the ground temperature attenuation and restoration characteristics of the buried pipe. Based on ground interpretation data, measured core thermophysical parameters, and logging temperature data, a three-dimensional numerical model for the U-type deep-buried pipe at a depth of 2,000 m was built. By adopting a constant flow rate and inlet temperature in the buried pipe as simulation conditions, this study calculated the heat transfer characteristic of the deep-buried pipe for five heat extraction periods and five heat restoration periods. The simulation monitored the changes in ground temperature in various heat extraction periods and heat restoration periods, analyzed the ground temperature attenuation and restoration characteristics, and compared the heat transfer rates of the buried pipe in various heat extraction periods. Based on the research results, although the ground temperature recovers to a certain extent during the heat restoration periods, it is still gradually attenuated with the extension of heat extraction periods. The heat transfer rate of the buried pipe in various heat extraction periods also gradually decreased but at a reduced pace.