Impingement Cooling in Rotating Two-Pass Rectangular Channels with Ribbed Walls

Abstract

Impingementcooling wasstudiedonribbed wallsinrotatingtwo-passrectangularchannelswith asharp 180-deg turn. Two rows of circular jets impinged opposite to the direction of rotation in one channel and in the same direction of rotation in the other channel. Square cross-sectioned ribs were periodically attached to the target walls and inclined at a 45-deg angle to the direction of spent aire ow. Rib pitch to height and rib height to channel hydraulicdiameterratiosweree xed at10 and0.125,respectively. Afterimpingement,spent air (crosseow)traveled radially outward and inward in the e rst and the second impingement channel, respectively. Jet Reynolds numbers and rotation numbers varied from 4 £ 10 3 to 1 £ 10 4 and 0 to 0.0133, respectively. As the jet Reynolds number increased from 4 ££ 10 3 to 1 £ 10 4 , the ratios of channel-averaged ribbed to smooth surface Nusselt numbers increased from 13 to 47% for the nonrotating test. For the rotating test, however, these ratios changed from 9 to 44% as the jet Reynolds number increased. Rotation-induced Coriolis and centrifugal forces altered the pressure distribution, but the jet velocity distribution was not signie cantly affected. However, those rotation-induced forces decreased the Nusselt number values up to 20% in the ribbed impingement channels.