Abstract:

A three-dimensional investigation of combined conduction, natural convection and radiation in vented enclosures is carried out.A discrete flush type heat source mounted on a vertical substrate is used to simulate an electronic component.A uniform volumetric generation rate is assumed within the heat source.Combined natural convection in the air,conduction in the heat source,the substrate and the enclosure walls and surface radiation are solved for Rayleigh numbers at 2.6 x 10⁶ and 2.0 x 10⁷.Radiation is incorporated based on the radiosity/irradiation approach.The resulting flow and temperature patterns are discussed, focusing on radiation and three-dimensional effects.The relative contributions of natural convection and radiation are investigated for different emissivities of internal surface of the substrate.Heat transfer rates from the substrate and other internal walls are presented to illustrate conjugate heat transfer due to combined modes.The numerical solutions are found in reasonably good agreement with the experimental data.