LBM-PFM simulation of the effect of non-condensable gas on the directional crystallization of seawater

Abstract

The present study employs the coupled Lattice Boltzmann Method-Phase Field Method (LBM-PFM) to investigate the impact of non-condensable gas bubbles on directional crystallization of seawater at the pore scale. Firstly, the LBM-PFM coupling model is proposed and experimentally validated. Subsequently, this model is applied to numerically simulate the two-phase (bubble -seawater) flow in directional crystallization. Additionally, the influence of factors such as bubble quantity, radius, and arrangement on ice crystal growth and the distribution, quantity, and area of internal brine pockets are discussed. The findings unequivocally demonstrate that the presence of non-condensable gas bubbles significantly enhances the rate of crystallization, resulting in a twofold increase in the area of freshwater ice. Bubbles with different radius, quantities, and spacing exert either promoting or inhibiting effects on the formation of brine pockets. Increasing bubble radius and quantity result in a larger area of freshwater ice crystals and a reduction in the quantity and area of brine pockets, ultimately resulting in an improved desalination efficiency. While changes in bubble spacing have a minimal impact on the generated ice crystal area, they significantly alter the distribution of brine pockets. Smaller spacing between bubbles leads to a lower number of brine pockets formed, thus inhibiting brine pocket generation.