Numerical simulation of experiments for wall condensation from mixtures of saturated steam and air in a vertical tube

Abstract

This study evaluates our previously proposed correlations for the wall condensation heat flux q_c and the wall functions of dimensionless profiles for temperature of steam and air mixture T_g and steam mass fraction X_s. These correlations are expected to be used in computational fluid dynamics (CFD) analysis with coarse computation cells to evaluate thermal hydraulic behavior in containment vessels (CVs) of nuclear power plants under accident conditions. We carried out numerical simulations of experiments for wall condensation from mixtures of saturated steam and air in a vertical tube (diameter, 49.5 mm) by using the CFD code FLUENT, compared the simulated T_g and q_c values with measured values, and evaluated the profiles of dimensionless mixture temperature T⁺ and steam mass fraction Y_s⁺ which are used for wall functions in turbulent analyses with coarse computation cells. We determined the simulated T_g and q_c values agreed with the measured values within uncertainties, but the decrease of q_c in the flow direction was not well simulated. The computed T⁺ values were smaller than the measured values but almost within the uncertainty, and the computed Y_s⁺ values agreed well with the measured values obtained from the assumption of the saturated conditions (i.e. T_s = T_g). These results confirmed that our previously proposed correlations for the q_c and wall functions can be used in a CFD analysis with coarse computation cells.