Heat Fluxes for Natural Convection Condensation on a Vertical Flat Plate from Steam and Air Mixtures

In this study, numerical computations of condensation heat fluxes along a vertical flat plate from steam and air mixtures in a rectangular flow channel with a condensation height of 6 m were carried out using the computational fluid dynamics (CFD) code FLUENT to evaluate condensation heat fluxes qc on the containment wall under accident conditions. The distributions of the computed heat flux qx,CFD values along the flow direction x agreed relatively well with those of the qx,exp values measured with the COPAIN facility with a condensation height of 2 m at a steam mass fraction of Ys,in = 0.133–0.233, and the standard deviation of the qx,CFD values to the qx,exp values was s = 13%. The qx,CFD values were numerically obtained with a mixture velocity range of uin = 0.27–3.2 m/s at Ys,in = 0.453, and they were compared with the qc,NC values computed by existing correlations for natural convection (NC) condensation. A combination of a qc correlation and a correlation for the Sherwood number Shx,NC in the qc correlation was evaluated, the coefficient for Shx,NC was optimized, and the standard deviation of the qx,NC values to the qx,exp or qx,CFD values was s = 16%.