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Chimney Effect on Natural Convection Cooling of Electronic Components
Keywords: chimney effect, natural convection cooling, dynamic analysis
The thermal impedance Zth(j*omega) has been measured for a transistor fixed on a small cooling fin. We have put the setup inside a cilindrical chimney with an inner diameter around 5cm and various heights H ranging from 20 to 60cm. The enhancement of the natural convection cooling by the chimney is clearly demonstrated by means of Nyquist plots of the thermal impedance. Depending on the insertion distance of the setup into the chimney, the case-to-ambient thermal resistance DeltaRth could be reduced by more than 15%. We also propose a simple hydraulic model for the chimney. The theoretical analysis predicts that 1/DeltaRth is proportional to H^(1/4). The experimental results agree quite well with this tendency.
Bjorn Vermeersch, Ph.D. Student - Research Assistant
Ghent University - Dept. of Electronics & Information Systems
Gent, Eastern Flanders 9000,
Belgium


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