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 qc and the wall functions of dimensionless profiles for temperature of steam and air mixture Tg and steam mass fraction Xs. 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 Tg and qc values with measured values, and evaluated the profiles of dimensionless mixture temperature T + and steam mass fraction Ys + which are used for wall functions in turbulent analyses with coarse computation cells. We determined the simulated Tg and qc values agreed with the measured values within uncertainties, but the decrease of qc 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 Ys + values agreed well with the measured values obtained from the assumption of the saturated conditions (i.e. Ts = Tg). These results confirmed that our previously proposed correlations for the qc and wall functions can be used in a CFD analysis with coarse computation cells.