Steady, laminar flow and heat transfer, inside a rectangular microchannel with a dimpled bottom surface, are numerically studied using FLUENT 5.5. The microchannel is 50 μm deep and 200 μm wide. The dimples are placed in a single row of along the bottom wall with a pitch of 150 μm. The dimple depth is 20 μm, and the dimple print diameter is 98 μm. Fully developed periodic velocity and temperature boundary conditions are used at the inlet and outlet of one unit cell of the dimpled micro-channel. The numerically predicted, laminar, micro-scale flow characteristics are compared to results from macro-scale studies with turbulent flow. Some of the secondary flows into and out of the dimple, and the recirculating flow within the dimple are similar for both situations. However, the type and number of vortex structures shed from the dimples are significantly different for the laminar-micro-scale flow and turbulent-macro-scale flow. Heat transfer enhancements are present for both situations, but they are somewhat smaller in the laminar-micro-scale flow. In the latter case, these augmentations (relative to a channel with smooth walls) are present both on the bottom-dimpled surface, and on the sidewalls of the channel, and are mostly due to shear layer reattachment, secondary flows produced near the edges of the dimples, and thermal boundary layer thinning. The pressure drop penalties in the laminar-micro-scale flow are either equivalent to, or less than values produced in smooth channels with no dimples.
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