Numerical investigation of coupled natural convection and radiation in a differentially heated cubic cavity filled with humid air. Effects of the cavity size
Résumé
A numerical study of natural convection with surface and air/H 2 O mixture radiation in a differentially heated cubic square cavity is presented. The coupled flow and heat transfers in the cavity are predicted by coupling a finite volume method with a spectral line weighted sum of gray gases model (SLW) to describe gas radiative properties. The radiative transfer equation (RTE) is solved by means of the discrete ordinates method (DOM). Simulations are performed at Ra = 10 6 , considering different combinations of passive wall and/or gas radiation properties and different cavity length. It was found that in presence of a participative medium representative of building, cavity length has a strong influence on temperature and velocity fields which affect the global circulation and the heat transfers in the cavity. For each steady state solution, the convective and radiative contributions to the global heat transfer are discussed. More specifically, boundary layers thickness, thermal stratification parameter and three-dimensional effects are compared to pure convective case results. The results suggest that radiative effects, often considered as negligible in view of the relatively low optical thickness, may not be neglected when trying to predict regime transitions.
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