Lattice Boltzmann modeling of pool boiling with large liquid-gas density ratio

Abstract

In the present paper, a 2D multiple-relaxation-time pseudopotential lattice Boltzmann model combined with the modified thermal lattice Boltzmann method is adopted to simulate the bubble nucleation, growth and departures process on a heated plate. It is a direct numerical simulation of boiling heat transfer determined by the local temperature and thermodynamic relation given by the equation of state. By using a smaller value of a in the P-R equation of state, a thicker liquid-vapor interface is formed and a better numerical stability at a large liquid/vapor density ratio is obtained. Furthermore, the conjugated boundary of heated plate and fluids is specially dealt with to avoid the rapid change of heat flux at the interface. The boiling heat transfer at a density ratio around 200 can be simulated. The results show that: the boiling heat flux decreases during the bubble expansion process while increases during the rewetting process; the average heat flux of boiling at Ts = 0.68Tc is much larger than that at Ts = 0.86Tc; bubble occurs earlier on a hydrophobic surface than a hydrophilic one; there exists a remained vapor on a hydrophobic surface after bubble departure, while it is not observed for hydrophilic surface; for the simulated boiling curve, the maximum (critical) heat flux decreases with the decreasing wettability of surfaces; there exists an optimal width of the rectangular cavity making the best heat transfer performance of surfaces; in this study, the roughness surface with a circle cavity has the best heat transfer performance.