DEVELOPMENT OF A PHENOMENOLOGICAL MODEL FOR THE PREDICTION OF DRYOUT LOCATIONS UNDER FLOODING-LIMITED CRITICAL HEAT-FLUX CONDITIONS

Abstract

A physical model for the prediction of dryout locations in a boiling channel with a closed bottom end is developed on the basis of the liquid film dryout model and the two-phase mixture level theory. It is assumed that the first dryout occurs at the boundary between the two-phase mixture region and the countercurrent annular flow region in the present boiling system. The mass and energy conservation equations are applied to the liquid film assuming no entrainment from the film region. A drift flux formulation is used for the calculation of the void fraction in the two-phase mixture region. In view of the results compared with Katto's experimental data, the present model is found to predict the upper and lower bounds of the dryout locations measured in the boiling system with a closed bottom end. The model accuracy improves as the length-to-diameter ratio increases.