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Corresponding Author

El-Kady, M.

Subject Area

Mechanical Power Engineering

Article Type

Original Study

Abstract

Laminar mixed convection in a porous channel with two discrete heat sources on the bottom wall was performed experimentally. The main object is to show the effect of using the porous medium in the channel on the heat transfer characteristics. Therefore, three cases were presented; non-porous channel, fully filled porous channel, and partially porous channel, in which the passages above the heat sources are filled with porous layers. A channel of 120x120mm cross section and length of 200mm is fitted in a low turbulence wind channel. The air flow velocity was varied up to 5 m/s which gives a variation of Reynolds number up to 104, heat flux was varied up to 7017W/m2. Aluminum porous filtration screen sheets of 3mm thickness, with porosity of 0.95, permeability of 1.28x10-8m2, density of 122.85 kg/m3 and Darcy number = 8x10-6 were used as porous layers to form the porous medium. The results show great effect of using the porous layers on both the temperature and heat transfer. The presence of the porous matrix causes a high resistance to the flow and slows it down and increases the pressure drop along the test seetion. It also, decreases the local and maximum temperatures along the heat sources to about one third of that for the non-porous channel. It increases the average heat transfer coefficient and average Nusselt number of both beaters by about 253 and 296 percent at Re = 1723 and 5531 respectively. The results for the partially porous channel indicate that almost the same increase in heat transfer, the same decrease in the temperatures and a significant reduction in pressure drop can be obtained compared with the fully porous channel. Therefore, the technique of using partially porous channel appears to be promising for application to electronics cooling.

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