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ISSN Online: 2377-424X

International Heat Transfer Conference 12
August, 18-23, 2002, Grenoble, France

Enhanced natural convection in a narrow channel between two vertical conducting plates with discrete strip heaters

Get access (open in a dialog) DOI: 10.1615/IHTC12.1910
6 pages

要約

Experiments are conducted to investigate natural convection of air in a vertical channel between two thin, vertical metal plates, 1.2 mm wide and 0.86 m high. One plate is made of aluminum (0.475 mm thick) and insulated on the outside and the other is made of stainless steel (0.318 mm thick) and has discrete horizontal heating elements mounted on its outer surface, simulating heat dissipated by electronic components that are vertically separated in tall cabinets. The heating elements are insulated on the outside to minimize conduction losses. The separation-to-height ratio of the plates varies from 0.044 to 0.35, and the vertical separation distanceto-width ratio of the heating elements is 3, 7, and 15. The experimental local Nusselt number is correlated in terms of Rayleigh number, Raq. Both Nusselt number and Raq are based on the average heat flux at the inner surface of the heated stainless steel plate, after subtracting radiation losses to the adiabatic aluminum plate and to the ambient. Results showed up to 50% enhancement in the cooling rate by natural convection, over that of an isoflux vertical plate in an infinite medium, when Raq ~ 2.3×1011. The heat transfer enhancement decreases as Raq decreases, becoming nil at Raq ~ 3×107, and drops below that for an isoflux vertical plate in an infinite medium at lower Raq, due to the deceleration of airflow in the unheated vertical spaces between the heating elements. Measurements of the temperature distribution in the boundary layer next to the heated plate, at different elevations, confirmed that in the experiments the airflow in the channel is in the laminar regime.