Experiments have been performed to assess the effect of four different longitudinal and offset strip fin arrangements on heat transfer from a small (12.7 mm #xD7; 12.7 mm), liquid-cooled heat source mounted flush with one wall of a rectangular duct. In terms strictly of thermal performance, the largest heat transfer enhancement is clearly associated with an offset arrangement and amounts to factors of more than 9 and 20 in water and a dielectric fluorocarbon (3M FC-77), respectively. However, on the basis of a fixed pressure drop, the preferred offset strip fin is only marginally superior to the other fins and there is, in fact, little difference between the four arrangements. On the basis of equal pumping power, one of the offset strip fins is clearly superior, but either of the offset fins would be preferred to the longitudinal fins in order to minimize the flow rate and overall pressure drop/pumping power. Standard Nusselt number correlations do not well predict the present data.
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