Local heat transfer measurements of an orthogonally rotating square duct with angled rib turbulators

Abstract

The effects of angled rib turbulators on the heat transfer of an orthogonally rotating square straight duct were experimentally investigated. The Reynolds number based on mean velocity and hydraulic diameter was varied from 10 000 to 20 000 and the Rotation number from 0 to 0.08. The leading and trailing walls were rib-roughened with angle-of-attack of 90 or 60 degree. The rib height-to-hydraulic diameter ratio was 0.1 and the rib pitch-to-hydraulic diameter ratio was 1. The results showed that the angled rib case gave higher heat transfer than the results of a 90 deg rib duct and a smooth duct. Judging from the local heat transfer variation, the skewed secondary flow induced by the angled rib seemed to give additional contribution to the heat transfer enhancement. The rotation made the heat transfer of the pressure side higher and that of the suction side lower, although the overall Nusselt number stayed almost constant within the present experimental range.