Improvement of Physical Modeling for Coupled Heat and Mass Transfer in a Square Cavity with Condensation in the Presence of Non-Condensable Gas
Résumé
During accident scenarios, pressure increase in the containment building caused by steam release is significantly limited by condensation on the wall. The comprehension of this mechanism requires a reliable physical model of the coupled heat and mass transfer inside a binary gas mixture involving a noncondensable species. In this paper, we develop such a model for natural convection of a mixture of airand vapor in a two-dimensional square cavity.
The flow velocity being small enough compared to sound speed, the low Mach approximation is taken to filter acoustic waves. The specificity of our model compared to the classical double diffusive approach, is to take into account the species interdiffusion phenomenon of a mixture of two gases with eventually different specific heat ratios. A Pressure-Implicit algorithm with Splitting Operators (PISO) is implemented with OpenFOAM to solve the model with a special treatment of the boundary conditions based on the partial velocity of air. Mesh convergence is established and comparisons with the double diffusive model are made.
Our analysis shows that species interdiffusion represents an important amount of the heat transfer and that
without its presence, the balance of heat fluxes cannot be ensured at steady state. The existence of interdiffusion also modifies the diffusive heat flux. Influence on the convective heat transfer. These two corrections need to be taken into account in further research.