WIT Press

Investigation On Mixed Convection In A Horizontal Channel Heated From Below


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O. Manca, S. Nardini & V. Naso


In this work mixed convection in a horizontal channel with the lower wall heated at a uniform heat flux is studied experimentally. The experiments are performed in air. The analysis is accomplished for several heat fluxes and forced air velocities. The Reynolds numbers investigated are between 10 and 500, these being in the laminar regime. The Richardson number Ri=Gr/Re2 holds values in the range 0.1–100. Flow visualization is performed to detect the flow patterns into the channel. The wall temperature distribution is given as a function of the Gr/Re2 values. Keywords: mixed convection, electronic cooling, material processing, thermal control. 1 Introduction Mixed convection in channels has received great interest for its engineering applications such as thermal control of electronic equipments and chemical vapor deposition (CVD). In horizontal channels heated from below, the buoyancy force can induce secondary flow that can lead to enhance the local heat transfer. The onset point of the secondary flow is important because it delineates the region after which the two-dimensional laminar flow becomes three-dimensional [1,2]. The unstable and stable vortex flow associated to the secondary flow is advantageous for some application such as cooling of electronic equipments [3]. In other technological applications such as in the CVD processes used to grow thin crystal films on silicon substrates, the presence of the vortex flow will result in a non-uniform deposition on the substrates [4]. Both the stable and unstable vortex flows should be avoided in the CVD processes. It has been found [1,2,5,6] that onset of the secondary flow and the enhancement of the heat transfer


mixed convection, electronic cooling, material processing, thermal control.