Condensation heat fluxes from mixed convection flows of steam and air mixtures on a vertical flat plate

Condensation heat transfer with mixed convection flows of steam and air mixtures, where the flow changes from forced convection to natural convection, was evaluated by using the CFD (computational fluid dynamics) code FLUENT to present a suitable correlation for condensation heat fluxes as one of the boundary conditions in CFD analysis for thermal hydraulics in the containment vessel of a nuclear reactor under accident conditions. Two-dimensional computations made for condensation experiments of steam and air mixtures on a vertical flat plate in the SETCOM facility with the cooling height of 6 m were in good agreement with the computed and measured heat fluxes, qCFD and qexp, in forced convection flows with the mixture velocities of 2.98–4.68 m/s (the average values of 1−qCFD/qexp were about 0.01 except the case with small qexp values). Computations changing the mixture velocities from 5.33 m/s to 0.27 m/s confirmed the change from forced convection flow to natural convection flow via mixed convection flow, and the computed heat fluxes were well expressed by the existing correlations for the forced convection and natural convection flows (the standard deviations of the qCFD values to the q values computed with the existing correlation were s = 2.2 and 6.6% for the forced and natural convection flows, respectively).