Conjugate Heating Inside a Large Aspect Ratio Cavity with Finite Conductive Walls

Abstract

In this work, the transient two-dimensional conjugated (conduction–natural convection) heating of a fluid in a rectangular large aspect ratio cavity (height to length ) is studied, with solid conductive walls of finite thickness. The equations of motion, written in nondimensional form, depending on five nondimensional parameters (the Rayleigh and Prandtl numbers, the ratio of the thermal conductivities and diffusivities of the fluid, the material of the cavity, and the nondimensional width of the walls), are solved numerically by the use of the SIMPLE algorithm. Three different heat transfer regimes were detected. The first one is the diffusive and quasi-diffusive, where heat is rapidly transferred along the cavity walls and then transmitted to the fluid from the internal boundary of the cavity, being almost independent on the Rayleigh number with a symmetrical response of the temperature and velocity fields. The second is diffusive-convective, where convection plays a more important role than in the previous case, symmetry is no longer preserved and different mechanisms of symmetry breakdown are present. The third one is the convective regime, where heat conduction along the walls is negligible and they can be assumed to be perfect insulators. Finally, it was found that the presence of conductive walls helps to stabilize and speed up the heating process, changing not only the magnitude of the heat flux to the system, but the physical response of the fluid inside the cavity.