Lattice Boltzmann simulation of coupled depressurization and thermal decomposition of carbon dioxide hydrate for cold thermal energy storage

CO₂ hydrate is a potential cold thermal energy storage material with latent heat of 500 kJ/kg, however, the dissociation principle of CO₂ hydrate is different from that of solid-liquid phase change materials and therefore, exploring the dissociation mechanism of CO₂ hydrate is of great significance for efficient cold storage. In this paper, a new lattice Boltzmann model is proposed, considering dissociation kinetics, two phase flow, heat transfer, latent heat, surface reaction, thermal buoyancy and variable parameter depended with temperature. The necessity of the temperature consideration related with latent heat and buoyancy is clarified. For the combined effect of depressurization decomposition and thermal decomposition of CO₂ hydrate dissociation, depressurization decomposition diminishes as time increases and initial pressure increases and thermal decomposition enhances as hot wall temperature increases. The fully dissociated Fo is 0.544, 0.514, 0.604, 0.628, showing a first decreasing and then increasing trend while initial pressure increases from 0 to 0.002, 0.004, 0.006 lu. As hot wall temperature increases from 8, 10, 12–14 °C, the fully dissociated Fo is 0.566, 0.544, 0.473 and 0.419 respectively. This new lattice Boltzmann model is of significance in providing guidance for the future cold thermal energy storage system application by using CO₂ hydrate.