Heat transfer augmentation using a rib–dimple compound cooling technique

Detailed distributions of the heat transfer coefficients in the channel with both angled ribs and dimples were measured using the transient liquid crystal technique. For comparison, heat transfer coefficients for dimpled and angle ribbed channels were also presented. The channel aspect ratio was designed to be 2 and 4 in order to simulate the internal coolant passage of a gas turbine blade. The rib pitch, rib angle, dimple diameter, and dimple center-to-center distance were 6 mm, 60°, 6 mm, and 7.2 mm, respectively. The Reynolds number based on the channel hydraulic diameter ranged between 30,000 and 50,000. Results show that the distribution of heat transfer coefficient was asymmetric due to the secondary flow induced by the angled ribs. Also, dimples fabricated between the ribs increased the heat coefficient with an acceptable increase in pressure drop. Thus, the compound cooling technique with angled rib sand dimples should be considered as a candidate for improving the heat transfer performance of a gas turbine blade internal cooling technique.