Analytical Model for Heat Transfer Accounting for Both Conduction and Dispersion in Aquifers With a Robin-Type Boundary Condition at the Injection Well

In the past, the analytical model developed for a radially divergent heat flow in an aquifer thermal energy storage (ATES) system considers only the process of either thermal conduction or thermal dispersion. In addition, the existing models commonly regarded the inner boundary at the injection well as the constant-temperature condition, which does not meet the continuity condition of heat flux at the wellbore. We herein propose an analytical model for a realistic representation of heat flow in an ATES system by considering the effects of both thermal conduction and thermal dispersion in the heat transfer equation and a Robin-type boundary condition at the injection well. The model consists of three heat flow equations depicting the temperature distributions in the confined aquifer and its underlying and overlying rocks. The Laplace transform method is applied to solve the proposed model. The solutions for the cases of dispersion- and conduction-dominant flow fields are also developed and discussed. Comparisons between the present solutions with five existing solutions developed for similar heated water injection problems are made. A global sensitivity method is also performed to analyze the thermal response to the change in each of the aquifer parameters. Finally, our solution is validated through the comparison with the finite difference solution and observed data from an ATES experiment site in Mobile, Alabama.