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ISSN Online: 2377-424X

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

Buoyant Plume Heat Transfer Impinging on Horizontal Downward-facing Surface

Get access (open in a dialog) DOI: 10.1615/IHTC12.2950
6 pages

Abstract

This paper presents an experimental study on impingement heat transfer from a buoyant plume to a horizontal downward-facing surface. Experiments are carried out for a plume produced by heating up a round stainless steel foil heater pasted on the center of the bottom upward-facing surface settled in parallel to the upper surface. The working fluid of this experiment is air. The diameter of the foil heater is selected as D = 100 and 300 mm, and the heat flux of the heater is changed from qb = 140 to 320 W/m2. Again a thin stainless steel square foil heater is pasted on the downward-facing surface of the top wall, and it can be heated electrically. The distance between the two surfaces is changed from H = 100 to 500 mm. Firstly the temperature at the stagnation point of the plume colliding on the top surface which is settled as an adiabatic condition is measured and defined as the adiabatic wall temperature of the top surface. Then the top wall is heated and the surface temperature at the stagnation point is measured again under the same plume impingement condition. The heat transfer coefficient is defined as the difference of these two surface temperatures. The obtained results are summarized as that the Nusselt number based on H is proportional to the power of 1/3 of the Rayleigh number based on H, which means that the heat transfer coefficient remains constant with the change of H. The reason of this result is considered to be the velocity of the impinging plume remains almost constant after the initial acceleration. The measurements of the flow velocity along the center axis of the buoyant plume confirm this hypothesis.