ABSTRACT
The present work investigates experimentally the heat transfer and flow
characteristics for an electronic module mounted on a simulated printed circuit
board placed downstream of a fence on the bottom wall of a duct with an aspect
ratio of 4. The module height (B) to channel height (H) ratio is fixed at B/H=0.317.
Three different values for the fence height (b) and four values for the spacing
between the fence and the module (S) were investigated in such a manner that the
ratio b/B=1, 1.5 and 2, and the ratio S/B=1, 2, 3, and 4. Reynolds number, based
on the streamwise length of the module (L), was ranged from 8000 to 40000. The
results for the module without fence displayed some noticeable differences as
compared to the smooth duct flow due to the existence of the separationreattachment
flow patterns. Secondary vortex tubes were existed at the module
sides due to the presence of the fence and these vortices have significant effects
on both the heat transfer and flow friction. Both Nusselt number and Fanning
friction factor are strongly dependent on Reynolds number while they are critically
dependent on both the fence height and spacing. A maximum Nusselt number
enhancement ratio (Nu/NuN-F) of about 1.94 was obtained corresponding to a
friction factor ratio (F/FN-F) of about 6.62. It was fount that the fence with b/B=1
provides the best performance based on the criterion of equal mass flow rate. New
correlations were obtained for the average Nusselt number and the Fanning friction
factor utilizing the present measurements within the investigated range of the
different parameters. |
