Based on the lattice Boltzmann method, the chemical reaction process of CO₂ absorption by tandem porous CaO particles is simulated at the scale of Representative Elementary Volume (REV) scale, and the influences of CaO porosity, particle diameter, and inter-particle arrangement of CaO particles on the conversion efficiency and the average conversion rate of particles are mainly investigated. The results show that the conversion efficiency of CaO particles first decreases and then increases with the increase of the porosity, which is attributed to differences in the initial amount of material and the internal gas-solid reaction rate of the particles due to the different porosities, and the competition between them affected the conversion efficiency. On the other hand, the larger the particle diameter, the lower the conversion efficiency. Specifically, the average conversion efficiency of the particles with 50 μm diameter is 8.4% higher than that of particles with 150 μm diameter, and the average conversion efficiency of particles with 150 μm diameter is 7.2% higher than that of the particles with 250 μm diameter. In addition, this work also investigates effect of the arrangement of particles on the average conversion rate. It is found that when the horizontal angle between particles changed from θ=0° to θ=10°, the average conversion rate can not be improved effectively with the increase of the angle due to the effect of the reflux vortex, and the average conversion rate is not improved with the increase of the angle between θ=10° and θ=40°. The average conversion between θ=0° and θ=10° is found not to be effectively improved due to the influence of the reflux vortex. And the average conversion between θ=10° and θ=40° is found to be significantly improved due to the fact that CaO particles at the rear are gradually moving away from the reflux zone, while the average conversion in the interval where the horizontal angle is larger than 40° is found to be maximized due to the fact that the average conversion is not changed with the angle. The simulation results can provide some theoretical guidance for CO₂ capture.

Natural convection of copper(Cu)-water nanofluids in a circular tube containing heat source with different shape (circular, triangular, and square) is numerically simulated with lattice Boltzmann method. Effects of Rayleigh number, nanoparticle volume fraction, and geometric shape of heat source on flow and heat transfer characteristics of the nanofluid are studied. It shows that heat transfer can be enhanced with increasing volume fraction of nanoparticles. And the increase of average Nusselt number in the case with small Rayleigh numbers is faster than those with large Rayleigh numbers. The largest average Nusselt number could be obtained in the square heat source case for all Rayleigh numbers considered. Finally, empirical prediction functions among average Nusselt number of the heat source surface, volume fraction of nanoparticles, and the Rayleigh number are presented. These relations provide predictions for engineering problems.

With a lattice Boltzmann two-phase flow model with large density ratio, we study dynamic behavior of a bubble as it passes through a porous media. It was found that as the porosity is large, the bubble deforms without breaking, and it passes completely through the porous medium; As the porosity is small, the bubble deforms violently and ruptures, and it takes more time to pass through the porous medium. In addition, as the contact angle of the porous medium is small, the bubble passes completely through the porous medium; As the contact angle increases, the bubble begins to rupture; The larger the contact angle is, the more seriously the bubble ruptures. The residual mass of the bubble decreases with the increasing of the contact angle. Moreover, it shows that as Eotvos number (Eo) increases, the proportion of surface tension decreases; The bubble ruptures more seriously; And the residual mass of the bubble passing through the porous media is smaller. It is found that the influence of wettability on residual mass of the bubble is the most obvious, and the influence of Eo is the minimum.