Heat and Solute as Tracers for Designing the Sustainable Groundwater Heat Pump (GWHP) Systems

Abstract

Higher efficiency and smaller space requirements make groundwater heat pump (GWHP) systems more preferable, especially for large heating and cooling plants. The design of GWHP systems is, however, highly dependent on the aquifer properties mainly due to the direct use of groundwater. Therefore, the aquifer characterization has a great importance in assessing the temperature anomalies and designing the efficient and sustainable GWHP systems. In this study, a total of 81 transport experiments on sub-meter scale using both heat and solute as tracers were performed at various background flow velocities (Re less than 0.32) to characterize the physical properties of fully saturated porous media (d50 less than 0.76 and U less than 1.50). Since heat and solute have different transport regimes at the same Darcy fluxes, this can enhance the characterization of the flow and transport processes and the prediction of the thermal plume propagation. Fluid EC and temperature time series data were analyzed by analytical and statistical models to derive the velocities and the dispersion coefficients of tracers. The estimated properties from solute transport experiments were compared with those from heat transport experiments. The results of this work can deepen our understanding of flow and transport processes in porous media, and improve the aquifer characterization and the design of the GWHP systems. [Acknowledgements] This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2017R1A2B3002119). This subject was also supported by National Research Foundation of Korea(NRF) grant funded by the Korea government(MIST)(0409-20190119).