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Abstract: This paper examines the steady natural convection in a partially opened enclosure filled with porous media using the Brinkman–Forchheimer model. Whilst the part of the left vertical wall of the cavity is heated, the other walls are adiabatic or thermally insulated Based upon numerical predictions, the effects of pertinent parameters such as Grashof number, Darcy number, porosity, length of the heated wall and the location center of the opened cavity are examined. It is found that as the Grashof number increases, due to strengthening buoyancy driven flows, the local Nusselt number from partially heated vertical wall, at a given position on this wall increases. This, in turn, increases the temperature of the heated wall. The results of this study can be used in the design of an effective cooling system for electronic components to help ensure effective and safe operational conditions. [Copyright &y& Elsevier]

Abstract: This paper conveys a numerical simulation of an active enhancement device for natural convection in the interfin spaces of a fin array. A baseline solution for the non-enhanced situation revealed that the confinement created by the walls of adjacent fins and the base surface gave rise to a drastic reduction of the heat transfer coefficient values compared with those for the standard vertical plate. This outcome demonstrated the necessity for enhancement. The enhancement device investigated here communicated with the interfin space via an opening in the base surface. Enhancement was achieved by alternately introducing and extracting air into and from the space. The frequency of the introduction/extraction cycle was varied over values of 0, 10, 50, and 100Hz. For each of these cases, spatially local, cycle-averaged heat transfer coefficients were determined on the bounding surfaces of the interfin space and on the outboard surface of a fin that faced a large ambient space. Results were also obtained for the cycle- and spatially averaged coefficients. Even at a low oscillation frequency of 10Hz, the interfin heat transfer coefficients were significantly enhanced but not sufficiently to overcome the confinement effect. At 100Hz, the enhancement gave rise to coefficient values that are about 64 times greater than the unenhanced values. [Copyright &y& Elsevier]