Dimple enhanced heat transfer in high aspect ratio channels

Detailed heat transfer measurements are presented for a rectangular channel with dimples on one wall. Dimpled surfaces provide high heat transfer enhancement comparable to ribbed surfaces with reduced overall pressure drop. The heat transfer coefficients were measured using a transient liquid crystal technique. The effect of the channel flow Reynolds number was investigated for a wide range from 10,000 to 65,000. The channel is a 25.4 mm x 101.6 mm (1" x 4") rectangular cross-section with dimples on one of the 101.6 mm walls. Heat transfer enhancement around three times that of a smooth channel was achieved for all flow conditions. The overall pressure drop through the dimpled section of the passage was also measured. The resulting thermal performance of the dimpled surfaces is significantly higher than that of channels with protruding ribs.