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Self-cleaning porous membrane can serve as condensing surface for its capacity of transporting condensate to the back through the pores thus keeping the surface clean during the whole condensing period. However, the three-dimensional (3D) condensate behaviors including the initial nucleation, growth and permeation in the porous structures have seldom been clarified comprehensively. In this work, the 3D pseudopotential LB model with a phase change model are employed, and the condensation process inside the porous membrane with various porosity, wettability, additional external force and section geometric configurations are investigated. It's found that with the increase of porosity, surface hydrophobicity and additional external force, more rapid penetration of condensate in the porous media and correspondingly faster removal rate of liquid can be obtained, and the subsequent vapor condensation is enhanced. But the nucleation time gets longer with high porosity and surface hydrophobicity. The additional external force has little effect on the nucleation time. Larger porosity and lower flow resistance inside the straight channel lead to higher condensation rate at the initial stage of condensation, while the porous structure with distorted pores with the same porosity contributes to improve the total condensation amount. This work helps to select the porous membranes with different porosity, wettability or pore scale geometric characteristic and external field for different condensation conditions in specific applications. [ABSTRACT FROM AUTHOR]

Fundamental understanding of coupled physicochemical processes is crucial for improving the heat storage/release performance of thermochemical heat storage systems. In this study, for the first time a coupled lattice Boltzmann model is developed to simulate the particle-scale physicochemical processes during Ca(OH) 2 dehydration, including fluid flow, heat transfer, vapor mass transport and chemical reaction. The dehydration processes of a single Ca(OH) 2 particle, a single particle with coated ceramic shell and packed particles are studied, and thorough parametric studies are performed. The results show that the dehydration reaction rate of a single particle is mainly determined by the temperature and Ca(OH) 2 concentration. Introducing more micro-pores or meso-pores into the particle is favorable to achieve quicker heat storage, but at the cost of lower energy density. Increasing the Reynolds number from 0.3 to 3 or increasing the inlet temperature by 50 K can shorten the reaction time t c by at least 33.8%. Dedicate design of the shell coated on the particle can enhance the dehydration process with t c decreased by 3.5%. The underlying heterogenous structures greatly affect the reaction rate of packed particles, and local cracks should be prevented to achieve fast and stable heat storage response. • Reactive transport process of Ca(OH) 2 dehydration at particle scale is simulated. • Temperature and solid concentration determine the dehydration of single particle. • Coating ceramic shell would increase the dehydration reaction rate of particle. • Structural heterogeneity strongly affects the dehydration of packed particles. • Effects of structural and operational parameters on the dehydration are studied. [ABSTRACT FROM AUTHOR]

Three immiscible fluids systems are often encountered in energy and environmental disciplines, especially in the oil exploration field. It is essential to enhance oil recovery (EOR) by identifying the three-phase fluid flow mechanism of oil-gas-water system in complex geological structures. In the present study, a lattice Boltzmann (LB) color gradient model for three immiscible fluid flow in three-dimensional porous media is employed and validated using five benchmarks (i.e., the multiphase spinodal decomposition; the multiphase Young-Laplace test; the liquid lens; contact angles and 3D channel layered three-phase fluid flow). The effects of wettability, viscosity ratio (M) and capillary number (Ca) on the relative permeability curves are analyzed in detail. When the wetting condition is enhanced, the results indicate that the relative permeability of non-wetting phase raises while that for the wetting phase exhibits a decline. When M is not equal 1, the relative permeability of high viscosity phase is significantly increased, while the other two phases are less affected. Meanwhile, the maximal value of relative permeability does not exceed unity because of the low porosity in the porous medium. For the influence of Ca , simulation results indicate the relative permeability shows weak sensitivity to Ca. • A lattice Boltzmann color gradient model for three-phase fluid flow is proposed. • Pore-scale three-phase fluid flow in porous media is studied. • Three-phase relative permeability is predicted. • Effects of wettability, viscosity ratio and capillary number are explored. [ABSTRACT FROM AUTHOR]