Direct numerical simulations of film boiling heat transfer by a phase-change lattice Boltzmann method

摘要

Numerical simulations of film boiling heat transfer on a horizontal surface are conducted in this paper using a modified pseudo-potential liquid-vapor phase change lattice Boltzmann model. A conjugate heat transfer problem, including heat conduction in the heater and its thermal responses during the film boiling process, is investigated. Unlike previous numerical studies which needed to initialize the shape of the liquid-vapor interface wave at the beginning of the computation, the computation domain for fluid region is occupied initially by saturated liquid in this paper. Taylor instability at the liquid-vapor interface is triggered by small temperature perturbations imposed at the bottom of the heater during a short initial period. Consequently, this paper represents a more direct and complete numerical simulation for film boiling heat transfer on a horizontal heater. The simulated time- and space-averaged Nusselt number is found in good agreement with a previous correlation equation. Temporal and spatial variations of the vapor film thickness are also investigated numerically and compared with existing correlation equations. It is demonstrated that the temperature at the top surface of the heart changes with position and time during the film boiling process. Although the transient film boiling patterns may depend on temperature perturbations imposed on he bottom of the heater during an initial period, the time- and space-averaged film boiling heat flux is independent of initial temperature perturbations.