Heat-Transfer Coefficients for Staggered Arrays of Short Pin Fins

Abstract

Short pin fins are often used to increase the heat transfer to the coolant in the trailing edge of a turbine blade. Due primarily to limits of casting technology, it is not possible to manufacture pins of optimum length for heat-transfer purposes in the trailing edge region. In many cases the pins are so short that they actually decrease the total heat-transfer surface area compared to a plain wall. A heat-transfer data base for these short pins is not available in the literature. Heat-transfer coefficients on pin and endwall surfaces were measured for several staggered arrays of short pin fins. The measured Nusselt numbers when plotted versus Reynolds numbers were found to fall on a single curve for all surfaces tested. The heat-transfer coefficients for the short pin fins (length to diameter ratios of 1/2 and 2) were found to be about a factor of two lower than data from the literature for longer pin arrays (length to diameter ratios of about 8).