This experimental study investigates the heat transfer in a narrow, rib-roughened, rectangular channel with the width-to-height ratio of 10 for its cross-sectional shape. Two flow entrances with equal areas are respectively opened at the upper and side ends of this channel that allows for increasing the coolant-flow fed into the enhanced channel without increasing the height of cooling device. At a fixed total coolant mass flow rate, three test scenarios, namely the single-blow from the side or upper entrance and the twin-blow with the coolant mass flow ratio of 2:1 between the side and upper blows are performed. A selection of detailed heat transfer measurements, evaluated from infrared thermal images over the rib-roughened surface, illustrates the manner by which the flow entry direction and the twin-blow condition affect the local and spatially averaged heat transfers. Relative to the heat transfer results acquired from the single-blow tests, the present twin-blow entry condition could augment the spatially averaged heat transfers to the levels of 150–180% of the single-blow reference levels. A regression-type analysis is subsequently performed to develop the correlation of spatially-averaged Nusselt numbers over rib-roughened surface, which permits the effect of Reynolds number, evaluated from the total amount of coolant consumption, on heat transfer to be determined for three test scenarios.

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