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First Thermal and Fluids Engineering Summer Conference

ISSN: 2379-1748
ISBN: 978-1-56700-430-4

NUMERICAL STUDY OF THE EFFECT OF VENT SIZE ON NATURAL CONVECTIVE HEAT TRANSFER FROM A SQUARE HORIZONTAL ISOTHERMAL HEATED SURFACE MOUNTED IN A FLAT ADIABATIC BASE AND SURROUNDED BY A PROTECTIVE COVER

DOI: 10.1615/TFESC1.fnd.012865
pages 1117-1127

Patrick H. Oosthuizen
Dept. of Mechanical and Materials Engineering, Queen's University Kingston, Ontario Canada K7L 3N6


KEY WORDS: Natural convection, Numerical, Horizontal surface, Natural ventilation, Covering surface

Abstract

In some applications electronic components are surrounded by a protective surface. This surface is usually vented to allow natural convective cooling flow of air over the . The vents in the protective surface must usually be small to ensure adequate protection. To investigate in a basic way the effect of vent size on the heat transfer rate in such situations heat transfer from a square, isothermal with a vented covering surface has been numerically studied. The covering surface is assumed to have a square crosssectional shape that just covers the heated element. The covering surface has a single inlet vent around the base of the covering surface and a single outlet vent around the top of the covering surface, these two vents having the same size. Conditions under which laminar, transitional, and turbulent flow can exist have been considered. The k-epsilon turbulence model with full account being taken of buoyancy force effects was used. The governing equations have been numerically solved using the commercial CFD solver ANSYS FLUENT©. The solution parameters are the Rayleigh number, the dimensionless size of the vents, the dimensionless height of the cover top above the heated element, and the Prandtl number. Results have only been obtained for a Prandtl number of 0.74. The effects of the dimensionless size of the inlet and outlet vents and of the dimensionless height of the top of the covering surface above the heated element on the mean Nusselt number for a range of Rayleigh numbers has been studied.

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