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This problem treats about the natural convection, a typical study in enclosed cavities with electronic components, as processors heating or in a simple DVD player, with devices inside generating a constant heat flow.

NATURAL CONVECTION IN CUBIC CAVITY WITH HEAT SPENDTHRIFT IN INFERIOR SURFACE by Rogério Fernandes Brito

ABSTRACT: The heat transfer for laminar natural convection in confined spaces is of great interest in the engineering field. The flow that occurs in a cavity is an important physical phenomenon that it must be investigated, once that can be applied in projects of average electronic components of electrical circuits with installed heat spendthrifts. The objective of the tested numerical model consists of verifying the quantity of heat wasted by fins, besides visualizing the velocity field and the isothermal lines in the fluid (air) and in the solid (aluminum). The surface of the electronic component is kept in the high isothermal temperature. The vertical surfaces are kept in the low isothermal temperatures. The inferior horizontal surface, around of the electronic component, is considered adiabatic. The superior horizontal surface also is considered adiabatic in the present work. In the inferior surface of the electronic component, sixty-four heat spendthrifts of the rectangular type are installed. The solutions for low values of Rayleigh are gotten, keeping the fixed Prandtl's number in 0.70. The Computational Fluid Dynamics is applied (ANSYS CFX-v11.0 SP1), which uses the Finite Volume Method (MVF), with Eulerian scheme, which is used to solve the conservative equations for the unsteady state. It is elaborated a 3D model with enough great width to eliminate the wall effect in calculation and to compare the results with 2D cases from literature. So, this work shows that the increase of the Rayleigh´s number, the heat transfer is increased too. Besides, it is presented that the heat spendthrifts permit to increase the heat transfer.

Keywords: Natural convection, finned cubic cavities, heat spendthrifts, CFD.

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