An improved three-dimensional thermal multiple-relaxation-time lattice Boltzmann model for liquid-vapor phase change

In this paper, an improved three-dimensional (3D) thermal multiple-relaxation-time (MRT) lattice Boltzmann (LB) model is proposed for the temperature field and coupled with a 3D central-moment pseudopotential LB model for the flow field to simulate liquid-vapor phase change, with the temperature field solved on the D3Q7 lattice. In contrast to previous models, the present model decouples the latent heat from the equation of state (EOS) through a reformulated source term, so that the latent heat becomes an independent parameter. This flexibility enables control of the vaporization rate and helps match dimensionless numbers such as the Jakob number. A Chapman-Enskog analysis confirms that the improved thermal LB equation correctly recovers the target macroscopic temperature equation without requiring an additional correction term. In addition, a non-orthogonal transformation matrix with more zero entries is constructed to simplify the collision step on the D3Q7 lattice. The model is validated through five benchmark cases of increasing physical complexity, ranging from heat transfer across a static liquid-vapor interface to pool boiling over a wide range of wall superheats. The numerical results agree well with reference solutions and experimental data, reproduce the expected power-law dependence of the bubble departure diameter on gravitational acceleration, and capture the boiling curve with nucleate, transition, and film boiling regimes. The simulated critical heat flux (CHF) agrees well with the Zuber correlation, with a relative deviation of 2.33%. The present model provides an accurate, flexible, and efficient tool for evaporation and boiling simulations, with potential for engineering applications.