Predicting critical heat flux in slug flow regime of uniformly heated vertical channel using coolant and geometric parameters

Numerical computation code (PWR-DNBP) has been developed to predict Critical Heat Flux (CHF) of forced convective flow of water in a vertical heated channel. The code was based on the liquid sub-layer model, with the assumption that CHF occurred when the liquid film thickness between the heated surface and vapour in the slug flow regime attained critical film thickness of infinitesimally small value at positive liquid velocities for which the value of critical heat flux ratio (CHFR) ~ 1. The numerical simulations predicted trends that CHF decreased with increasing flow quality, increased with increasing coolant mass flux, and increased with channel diameter. The predicted CHF were validated with data obtained by Tong’s correlation, and the computational errors indicated deviations of 5 -10 % uncertainty levels.