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Experimental Evaluation of the Heat Transfer Coefficient in Electronic Air-Cooling
Mourad Rebay, Sadık Kakaç, Rejeb Ben-Maad and Jacques Padet

As a contribution to the development of the thermal management of the cooling of electronics, a measurement technique of the convective heat transfer coefficient on the electronic wiring boards is presented here. The technique consists of measuring, by the infrared thermography, the temporal evolution of the thermal field on the electronic board during its normal functioning and after supplying of additive luminous energy. The technique was tested on the mainboard of a personal commercialised computer. Whereas, it may be used in characterization of the heat transfer on the electronic cards that are included in desktops and laptops computers, telecommunications servers, automotive and aerospace engines. The convective heat transfer coefficient was evaluated between the main microprocessor and the air-flow in the direction parallel to the printed board. The evaluation method consists of analysing the transient temperature of the microprocessor after a sudden energy pulse with a fixed duration given by two lamps. For the validation of the method, two cooling configurations were tested and evaluated. The first one considers the air-flow in the lengthwise of the main wiring board, and the second one concerns the case where the flow is along the widthways. In each configuration, the heat transfer coefficient was evaluated for three flow velocities.

Keywords: Electronic cooling, Infrared Thermography, forced convection, photothermal, pulsed method, Microprocessor

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