medium-deep geothermal energy, ground heat exchanger, heat transfer, heat extraction, thermal influence radius, circulating fluid, underground rock and soil

 Presents the structure and working principle of medium-deep geothermal energy double tube heat exchangers, and establishes the energy control equations for the circulating fluid in the heat exchange tubes and the rock and soil media around the borehole. Taking a ground source heat pump project as an example, analyses the effects of drilling depth, circulating fluid flow and geothermal flow on the nominal heat extraction of ground heat exchangers, as well as the changes of both the inlet and outlet temperatures of the circulating fluid, the thermal influence radius of ground heat exchangers, and the temperature distribution of the borehole wall. Reveals the changes of the heat extraction and the relevant parameters of circulating fluid and underground rock and soil during project operation.