Publication de 8 numéros par an
ISSN Imprimer: 1065-5131
ISSN En ligne: 1563-5074
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NUMERICAL INVESTIGATION ON EFFECTS OF SECONDARY FLOW INTO DUCT FOR COOLING OF THE RIBS BY PASSIVE ENHANCEMENT METHOD
RÉSUMÉ
A numerical investigation of hydrodynamic and forced convection heat transfer in a three-dimensional rectangular horizontal duct was conducted. Heat sources were cross-rectangular ribs with small aspect ratio and uniform heat flux a under turbulent regime. The purpose of this study is application of a passive enhancement method to increase the rate of heat transfer from the ribs. The geometry and physics of the problem are similar to cooling of electronic boards. Therefore three rectangular ribs were established along the width of the channel with specified distance from each other. Between ribs some vortexes appeared, which generally acted as heat traps and thus reduced the heat-transfer rate. These thermal resistances should be neutralized by applying heat-transfer enhancement methods. Due to the low pressure of these areas in comparison with their surrounding environment, establishing holes between the ribs is an appropriate method for vanishing the heat traps. Actually, by applying holes between the ribs, some distortions in the vortex patterns are made and an enhancement in the heat transfer due to the existence of secondary flows are made subsequently. These phenomena occurred without any outsource energies. This method is classified as a passive method. Numerical simulation for the assumed geometry is performed by solving the governing equations infinite volume with PHOENICS software. The obtained simulated results indicate good agreement with experimental investigations reported by other researchers. In this work, the main airflow was produced in two cases of suction and blowing from a fan inside of the channel. A comparison between two cases of suction and blowing is different for pressure gradients. Different pressure gradients have been affected on heat transfer phenomenon. Comparisons between the plain and passive cases show that the performance evaluation criterion is highly dependant on the holes' geometric parameters, especially their numbers and arrangements. Nine different arrangements for holes with the same number of holes were studied comprehensively in this research.
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Alami nia Amin, Campo Antonio, Experimental study on EHD heat transfer enhancement from flush-mounted ribbons with different arrangements of wire electrodes in a channel, Heat and Mass Transfer, 52, 12, 2016. Crossref