The geothermal potential available from deep underground mines has yet to be utilized. However, stope coupled heat exchangers (SCHE) are aiming to take advantage of the unused low-grade geothermal energy. Backfilled stopes provide a unique opportunity to install non-linear heat exchangers, as the geometry is not limited to the shape of a borehole. Helical pipes deliver superior fluid mixing and heat exchange compared to straight pipes, due to the effect of the secondary flow within the helical pipe. The helical closed-loop geothermal heat exchanger enables the backfilled stopes of the mine to be repurposed as thermal energy storage units. This paper delves into the experimental results from a laboratory scale helical closed-loop heat exchanger with varying thermo-physical parameters. Additionally, a conjugate numerical model is developed and its results are validated against the base case of the experimental studies. The results of the numerical model suggest that the pumping rate through the SCHE has a significant effect on the heat exchange rate and the overall energy transfer between the SCHE and the backfill. © Published under licence by IOP Publishing Ltd.