Numerical prediction of critical heat flux in pool boiling with the two-fluid model

Abstract

Three-dimensional numerical simulations of the atmospheric saturated pool boiling are performed with the aim of predicting the critical heat flux. The two-phase mixture in pool boiling is described with the transient two-fluid model. The transient heat conduction in the horizontal heated wall is also solved. Dynamics of vapor generation on the heated wall is modeled through the density of nucleation sites and the bubble residence time on the wall. The heater's surface is divided into zones, which number per unit area equals the density of nucleation sites, while the location of nucleation site within each zone is determined by a random function. The results show a replenishment of the heater's surface with water and surface wetting for lower heat fluxes, while heater's surface dry-out is predicted at critical heat flux values. Also, it is shown that the decrease of nucleation site density leads to the reduction of critical heat flux values. Obtained results of critical heat flux are in good agreement with available measured data. The presented approach is original regarding both the application of the two-fluid two-phase model for the prediction of boiling crisis in pool boiling and the defined boundary conditions at the heated wall surface.