Consistent phase-change modeling for CO2-based heat mining operation

The accuracy of mathematical modeling of phase-change phenomena is limited if a simple, less accurate equation of state completes the governing partial differential equation. However, fluid properties (such as density, dynamic viscosity and compressibility) and saturation state are calculated using a highly accurate, complex equation of state. This leads to unstable and inaccurate simulation as the equation of state and governing partial differential equations are mutually inconsistent. In this study, the volume translated Peng-Robinson equation of state was used with emphasis to model the liquid-gas phase transition with more accuracy and consistency. Calculation of fluid properties and saturation state were based on the volume translated Peng-Robinson equation of state and results verified. The present model has been applied to a scenario to simulate a CO2-based heat mining process. In this paper, using temporal and spatial variations in pressure and fluid phase temperature, the energy capacity and how it is affected by fluid compression (Joule-Thomson effect) and convection was predicted. Results suggest that superheated vapor can be produced at a higher rate with elevated heat content as convection heat transfer is strongest in heat mines with smaller particle diameter, in which the Joule-Thomson effect may further enhance the energy content. (C) 2016 Elsevier B.V. All rights reserved.