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Transport Phenomena in Thermal Engineering. Volume 2

ISBN:
1-56700-015-0 (Print)

NATURAL CONVECTIVE AIR COOLING OF THE PCBs ARRAY IN A CLOSED CASING

Z. G. Wang
Lehrstuhl A für Thermodynamik, TU München, München, Germany

Franz Mayinger
Lehrstuhl A für Thermodynamik, Technische Universität München, München, Germany; Technical University, Hannover, FRG Institut fur Verfahrenstechnik

Abstract

An experimental investigation was carried out to study the natural convective air cooling of the printed-circuit-boards (PCBs) array which was set up vertically in a closed casing. The results show that there exists an unstable thermal boundary layer on the top wall, which brings about vortex flow and temperature oscillation in the casing. Because of the thermal instability the air circulation in the casing is unsteady. Time-varying recirculation presents in the PCBs array. Experimental results were correlated in the form of Nu = f(Ra,r) with Rayleigh-number ranging from 102 to 105 at Pr = 0.71.