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Impacts of injection temperature on the relevant heat transport processes in groundwater heat pump (GWHP) systems

Park, Byeong-Hak
Lee, Kang-Kun

In many hydrogeological applications, the influence of temperature on fluid density and viscosity have often been neglected. However, high contrasts in temperature which occurs in the field applications such as groundwater heat pump (GWHP) systems, can make the effects of variable density and viscosity on flow and transport significant. A theoretical study suggests that free convection occurs in an infinitely extensive horizontal layer when the Rayleigh number exceeds about 40. Experimental investigations are still lacking on the conditions where the influence of temperature can be important.

In this study, a laboratory experimental system was developed to investigate the impacts of injection temperature on the relevant heat transport processes. First of all, the experiments such as sieve analysis and constant-head permeability test were performed to estimate the physical properties of the saturated porous medium. Laboratory tracer tests using a resistor as a heat source were conducted with/without background flow conditions to derive the thermal properties of the medium. Lastly, tracer tests using injected water with different temperatures were performed to identify the certain conditions where the variations in fluid density and viscosity play an important role in the subsurface flow and transport.