Heat/mass transfer and pressure drop in a square duct with V-shaped ribs

The present study investigates the convective heat/mass transfer characteristics and pressure drop inside the rib-roughened cooling passage of gas turbine blades. The internal cooling passage is simulated using a square duct with Λ -and V-shaped rectangular ribs which have a 60 .deg. attack angle. A naphthalene sublimation technique is employed to determine the detailed local heat/mass transfer coefficients using the heat and mass transfer analogy. The ribs disturb the main flow resulting in the recirculation and secondary flows near the ribbed wall. The secondary flow patterns and the local heat transfer in the duct are changed significantly according to the rib orientation. A square duct with Λ -and V-shaped ribs have two pairs of secondary flow due to the rib arrangement. Therefore, the average heat/mass transfer coefficients and pressure drop of Λ -and V-shaped ribs are higher than those of the continuous ribs with 90 deg. and 60 .deg. attack angles. The Λ -shaped ribs have higher heat/mass transfer coefficients than the V-shaped ribs, and the uniformity of heat/mass transfer coefficient are increased with the discrete ribs due to the flow leakage and acceleration near the surface