A three dimensional investigation of turbulent flow and heat transfer around sharp 180-deg turns in two-pass rib-roughened channels

The characteristics of the turbulent flow and heat transfer around sharp 180 deg turns in relatively short two-pass rib-roughened channels were investigated numerically for the Reynolds number varying from 1.0x10⁴-9.0x10⁴ by using the standard K-ε model in conjunction with the wall function method. The rib height-to-hydraulic diameter ratio (e/D) is 0.05, and the rib pitch-to-height ratio is 10. The attack angle (α) is 90 deg in inlet and outlet straight duct. In addition, there are also oblique ribs (α=45) in the turn region. To verify the numerical results, experiments for the resistance coefficient and heat/mass transfer were conducted, and reasonably good agreement between numerical and experimental results was achieved.