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International Heat Transfer Conference 15

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

Inlet Flow Effects in Microchannels on Single-Phase Heat Transfer Coefficients and Friction Factors

Darshik V. Garach
Department of Mechanical and Aeronautical Engineering, University of Pretoria

Jaco Dirker
Department of Mechanical and Aeronautical Engineering, University of Pretoria

Josua Petrus Meyer
Department of Mechanical and Aeronautical Engineering, University of Pretoria, Pretoria, Private Bag X20, Hatfield, 0028, South Africa

DOI: 10.1615/IHTC15.fcv.009210
pages 3031-3045


KEY WORDS: Convection, Micro, Electronic cooling, Experimental, Laminar, Transitional Flow

Abstract

The influence of different inlet types on the heat transfer and pressure drop in rectangular small-scale channels was investigated experimentally in the laminar, transitional, and turbulent regimes. Three test sections consisting each of a single square channel with hydraulic diameters of 1.05 mm, 0.85 mm and 0.57 mm respectively and of length 200 mm, were used with water and operated at a constant surface heat flux boundary condition. The inlet geometry types under consideration were: sudden contraction, bellmouth and swirl. Results showed that the onset and Reynolds number range of transition were influenced by the flow effect at the inlet. Friction factors and Nusselt numbers were also dependent on the inlet flow effect. The bellmouth inlet type exhibited the longest transitional range, during which the heat transfer coefficient were enhanced by a larger margin than what the friction factor penalty increased by. Flow with the swirl inlet effect exhibited the highest friction factor and Nusselt numbers in all three flow regimes.

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