Heat transfer and pressure drop for short pin-fin arrays with pin-endwall fillet

Abstract

The effects of array configuration and pin-endwall fillet on the heat transfer and pressure drop of short pin-fin arrays are investigated experimentally. The pin-fm element with endwall-fillet, typical in actual turbine cooling applications is modeled by a spool-like cylinder. The arrays studied include an in-line and a staggered array, each having 7 rows of 5 pins. These arrays have the same geometric parameters, i.e. H/D = 1, S/D = X/D = 2.5, and the Reynolds number ranging from 5 × 10 3 to 3 × 10 4 One of the present results shows that the staggered array always has a higher array-averaged mass transfer coefficient than its in-line counterpart. However, the pressure drop for the staggered array is higher compared to the in-line configuration. These trends are unaffected by the existence of the pin-endwall fillet. Another significant finding is that an array with pin-endwall fillet generally produces lower heat transfer coefficient and higher pressure drop than that without endwall-fillet. This leads to the conclusion that pin-endwall fillet is undesirable for heat transfer augmentation. In addition, naive use of the heat transfer results obtained with perfectly circular cylinders tends to overestimate the pin-fin cooling capability in the actual turbine. The effects of endwall-fillet on the array heat transfer and pressure drop are much more pronounced for the staggered array than for the in-line array; however, they diminish as the Reynolds number increases.