Editorial to the Special Issue: Adsorption,Absorption and Thermochemical Transport Processes in Complex Porous Structures

Transport in Porous Media - The theme of coupling problems for adsorption, absorption and thermochemical transport in porous media is very important for engineering applications. Based on the...     

Correspondence Between One- and Two-Equation Models for Solute Transport in Two-Region Heterogeneous Porous Media

In this work, we study the transient behavior of homogenized models for solute transport in two-region porous media. We focus on the following three models: (1) a time non-local, two-equation model (2eq-nlt). This model does not rely on time constraints and, therefore, is particularly useful in the short-time regime, when the timescale of interest (t) is smaller than the characteristic time (?? ₁) for the relaxation of the effective macroscale parameters (i.e., when t?????? ₁); (2) a time local, two-equation model (2eq). This model can be adopted when (t) is significantly larger than (?? ₁) (i.e., when ${t\gg\tau_{1}}$ ); and (3) a one-equation, time-asymptotic formulation (1eq ^??). This model can be adopted when (t) is significantly larger than the timescale (?? ₂) associated with exchange processes between the two regions (i.e., when ${t\gg\tau_{2}}$ ). In order to obtain insight into this transient behavior, we combine a theoretical approach based on the analysis of spatial moments with numerical and analytical results in several simple cases. The main result of this paper is to show that there is only a weak asymptotic convergence of the solution of (2eq) towards the solution of (1eq ^??) in terms of standardized moments but, interestingly, not in terms of centered moments. The physical interpretation of this result is that deviations from the Fickian situation persist in the limit of long times but that the spreading of the solute is eventually dominating these higher order effects.     

Smouldering in fixed beds of oil shale grains. A three-dimensional microscale numerical model

A three-dimensional, microscale numerical model for the simulation of smouldering in fixed beds of solid fuels is presented. It solves the local governing equations, and therefore explicitly accounts for the coupling of the transport and reaction mechanisms on the microscopic scale. This article describes the conceptual and numerical apparatus and provides illustrative examples of calculations. Extensive applications will be presented in two companion papers.     

Simultaneous Determinations of Effective Porosity and Dispersion Coefficient from Core Flooding Experiments,Considering Chemical Reactions

Transport in Porous Media - The objective of this work is to develop and apply a numerical workflow for the simultaneous determinations of the effective porosity and the dispersion coefficient from...     

Three-phase free-water flash calculations using a new Modified Rachford–Rice equation

A novel Modified Rachford–Rice equation is developed for three-phase equilibrium calculations in hydrocarbon–water systems, based on the free-water assumption, i.e., the water-rich liquid phase consists of pure water only. In the inner loop of the flash algorithm, the three-phase problem (consisting in a system of two non-linear equations) is replaced by a pseudo-two-phase problem (consisting in a non-linear equation). Unlike previous formulations, the new Modified Rachford–Rice function is guaranteed to monotonically decrease between two adjacent asymptotes. The negative flash concept is used, and a search window is proposed for the vapor fraction. The new free-water flash method proved to be robust, and excellent agreement between full three-phase flash and pseudo-two-phase free-water flash was obtained for various test problems. The proposed method is very useful in compositional reservoir simulation of certain oil recovery methods and in process simulation.