A 3-DIMENSIONAL INVESTIGATION OF TURBULENT-FLOW AND HEAT-TRANSFER AROUND SHARP 180-DEG TURNS IN 2-PASS RIB-ROUGHENED CHANNELS

The characteristics of the turbulent flow and heat transfer around sha rp 180 deg turns in relatively short two-pass rib-roughened channels w ere investigated numerically for the Reynolds number varying from 1.0x 10(4)-9.0(x)10(4) by using the standard K-epsilon model in conjunction with the wall function method. The rib height-to-hydraulic diameter r atio (e/D) is 0.05, and the rib pitch-to-height ratio is 10. The attac k angle (alpha) is 90 deg in inlet and outlet straight duct. In additi on, there are also oblique ribs (alpha=45) in the turn region. To veri fy the numerical results, experiments for the resistance coefficient a nd heat/mass transfer were conducted, and reasonably good agreement be tween numerical and experimental results was achieved. (C) 1997 Elsevi er Science Ltd.