Steady, laminar flow and heat transfer, inside a rectangular microchannel with a dimpled bottom surface, are numerically studied. The microchannel is $50×10−6m$$(50μm)$ deep and $200×10−6m$$(200μm)$ wide. The dimples are placed in a single row along the bottom wall with a pitch of $150×10−6m$$(150μm)$. The dimple depth is $20×10−6m$$(20μm)$, and the dimple footprint diameter is $98×10−6m$$(98μm)$. Fully developed periodic velocity and temperature boundary conditions are used at the inlet and outlet of one unit cell of the dimpled microchannel. Key flow structures such as recirculating flow and secondary flow patterns and their development along the flow directions are identified. The impact of these flow structures on the heat transfer is described. Heat transfer augmentations (relative to a channel with smooth walls) are present both on the bottom-dimpled surface, and on the sidewalls of the channel. The pressure drops in the laminar-microscale flow are either equivalent to, or less than, values produced in smooth channels with no dimples. It is concluded that dimples, proven to be an effective passive heat transfer augmentation for macroscale channels, can also be used to enhance heat transfer inside microchannels.

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