Numerical research on geothermal energy extraction in backfilled mines by using the excellent heat transfer performance of loop heat pipe

Deep mine harbor substantial geothermal energy. Integrating a heat exchanger within the backfill body mitigates thermal hazards and facilitates the concurrent extraction of mineral and geothermal resources. Inspired by the capabilities of superior thermal conductivity, high heat transfer limit without additional energy consumption of loop heat pipe (LHP), a novel cemented paste backfill system coupled with an LHP heat exchanger (LHPHE-CPB) was developed to effectively improve the thermal conductivity of backfill body and enhance the extraction performance of geothermal energy in backfilled mines. The temperature evolutions of LHPHE-CPB system and the mechanisms of vapor-liquid phase transition and two-phase flow within LHP were numerically analyzed during the stages of heat storage and simultaneous heat storage/heat release. Orthogonal tests meticulously examined the effects of surrounding rock temperature, and the inlet temperature and flow rate of cooling water on the system's heat transfer performance. Optimal operating conditions for the system, in terms of reducing backfill body temperature, achieving favorable temperature differentials between the inlet and outlet cooling water, and enhancing the heat extraction capacity of system, were determined through range and variance analyses. This research establishes a theoretical foundation for the application of LHP in efficiently extracting geothermal energy from backfilled mines.