Transient combined natural convection and radiation in a double space cavity with conducting walls

Two-dimensional numerical analysis of transient conjugate heat transfer in a double space gas filled enclosure with conducting solid walls has been carried out. This configuration can be found in cooling process of some electronic equipment in which the generated heat must be removed to avoid failure. Natural convection equations in the enclosures are solved in terms of the dimensionless stream function and vorticity using finite-difference technique. The discrete ordinates method (DOM) is used to solve the radiative transfer equation (RTE) in the filling gases which are considered to be absorbing, emitting and scattering. The effects of Rayleigh number and optical thickness of two radiating media in transient cooling process from the hot surface toward the cold one are investigated. The transient results show that when the optical thickness of the gas layer closed to the heat source is lower than the second layer, more heat penetrates into the enclosure which consequently leads to higher cooling performance and lower rates of thermal failure.