THERMAL DISPERSION BEHAVIOR UNDER THE INDUCED FLOW FIELD BY THE GWHP SYSTEM

In the field-scale, the thermal dispersion is known to occur due to the heterogeneity of aquifer properties. This can be the reason why the macroscopic thermal dispersion has a wide range of values in the literature. The recent studies on the scaling behavior indicates that the macrodispersivity increases with travel distance to their asymptotic values. Therefore, the thermal dispersivity in the field-scale can be higher by several orders of magnitude than in the lab-scale.

In addition, pumping and injection in field applications can further increase the magnitude of thermal dispersion. Because the GWHP utilizes a great deal of groundwater as a heat source (or a heat sink), the great perturbation can occur in natural flow system. Under such condition, the influence of the thermal dispersion on the relevant transport processes can be increased.

In this study, lab-scale thermal tracer tests were performed to investigate the thermal dispersion behavior under forced flow field by injection. In the experiments, a resistor and warm water were used as point heat sources with various background flow velocities. The observed thermal breakthrough curves were analyzed by analytical and numerical models. The results suggest that the importance of thermal dispersion can vary with injection rates as well as background flow velocities

Acknowledgements

This work was supported by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (No. 2017R1A2B3002119). This study was also supported by the X-project of the NRF and the Geowater+ project in “Water Resources Management Program” of the MOLIT and the KAIA of Korea. Thermal monitoring was partly supported by the R&D project on Environmental Management of Geologic CO2 Storage from the KETTI (# 201400180003). The BK 21 PLUS project of the Korean government also supported this study.