Effect of nonuniform pin size on heat transfer in a rotating rectangular channel with pin-fin arrays

Internal channels to cool the trailing edges of gas turbine blades were typically installed with pin-fin arrays for higher heat transfer enhancement. In this study, the heat transfer characteristics in a rotating rectangular channel (aspect ratio = 4:1) with differently sized pin-fin arrays were experimentally investigated. Liquid crystal thermography was used to measure heat transfer on the endwall in a staggered pin-fin array at a channel orientation of 135 degrees. The staggered array was composed of four or three pins in a row. Pins of varying diameters were inserted in every row exhibiting four pins; either two or four pins were replaced. The rotation numbers ranged from 0 to 0.33, and the Reynolds numbers ranged from 10,000 to 20,000. The results revealed that flow acceleration, separation, and wake flow contributed to various heat transfer contours. Larger pins contributed to higher local flow velocities through fin spacing and produced higher heat transfer distributions. The effect of rotation improved heat transfer enhancement on both trailing and leading surfaces. The friction factor ratio increased when more large-sized pins were installed in the array.