Improved boundary conditions for lattice Boltzmann modeling of pool boiling at low temperature

The pseudopotential lattice Boltzmann method (LBM) becomes popular in simulating the boiling heat transfer problems. By using the interaction force determined from an equation of state, the boiling phenomenon can occur spontaneously according to the thermodynamics, which avoids using empirical models for boiling. However, this pseudopotential interaction model also brings additional cause of instability, which becomes severe at high density ratios. Therefore, most of its previous boiling simulations are conducted at high saturated temperatures with low density ratios. Since the instability usually stems from the disturbance at the interfaces, we investigated the scheme of computing the solid pseudopotential for the solid-fluid interaction and proposed using the average surrounding fluid properties as the virtual solid temperature in addition to density. Droplet evaporation and film boiling problems at high saturated temperatures are simulated, and very good agreement is obtained when compared with the available numerical and analytical solutions, respectively. We then applied the pseudopotential LBM model to simulate droplet evaporation and pool boiling at a low reduced temperature of T r = 0.592 with a density ratio of 1000, as demonstrations of the improved numerical stability. Different boiling regimes are observed by varying the superheat imposed at the bottom wall.