Pore-Scale Simulations Of Flow And Heat Transport In Saturated Permeable Media

Abstract:

The study of heat transport in porous media is important for applications such as the use of temperature as environmental tracer, geothermal energy, fuel cells, etc. In recent years, there have been several advances in computational techniques that have allowed to investigate different processes in porous media at the pore-scale through detailed numerical simulations that considered synthetic porous media formed by regular grains and pore bodies arranged in different geometrical configurations. The main objective of this research is to investigate the influence of pore configurations on flow velocity and heat transport in 2D saturated porous media. We use OpenFOAM to solve flow and heat transport equations at the pore-scale. We performed detailed pore-scale numerical simulations in synthetic 2D porous media generated from regularly placed and randomly distributed circular solid grains. For each geometrical configuration we performed numerical simulations to compute the flow field in order to calculate properties such as as tortuosity, mean velocity and hydraulic conductivity, and to identify Lagrangian coherent structures to charaterize the velocity fields. We then perform heat transport simulations to relate the properties of the velocity fields and the main heat transport mechanisms. The analysis of the simulations results showed that in all the simulated configurations effective flow properties become valid at scales of 10 to 15 pore bodies. For the same porosity and boundary conditions we obtained that as expected tortuosity in the random structure is higher than in the regular configurations, while hydraulic conductivity is smaller for the random case. The results of heat transport simulations show significant differences in temperature distribution for the regular and random pore structures. For the simulated boundary and initial conditions, heat transport is more efficient in the random structure than in the regular geometry. This result indicates that the simulated pore-geometry can have a large influence on effective parameters such as torutosity and heat transport parameters derived from results of pore-scale simulations, hence the generalization of those results to general pore geometries may be difficult or impossible.