Effects of Varying Streamwise and Spanwise Spacing in Pin-Fin Arrays

Pin-fin channels are commonly used for cooling the trailing edges in turbine blades and vanes. While many studies have investigated heat transfer performance of pin-fin channels, few studies have investigated pin-fin flowfields. The present study compares the time-dependent near wake flow and the time-mean surface heat transfer for varying pin-fin configurations at a Reynolds number of 2.0e4. Pin-fin aspect ratio showed little influence on pin-surface heat transfer coefficients when increasing H/D from 1.0 to 2.0. Changes in streamwise and spanwise spacing, however, were found to significantly impact the behavior of the near wake flow and local heat transfer coefficients. Decreasing spanwise spacing from S/D = 3.0 to 1.5 in a single pin-fin row was found to suppress downstream vortex shedding and create biased, asymmetric wakes. Local heat transfer coefficients on the trailing side of the pin-fin reflected that vortex shedding, observed for spanwise spacings S/D ≥ 2.0, was beneficial for heat transfer on the pin-surface. Similarly, decreasing streamwise spacing from X/D = 3.03 to 2.16 was found to suppress vortex shedding in the first row of a seven row array. For those cases that support vortex shedding, X/D ≥ 2.60, pin-fin heat transfer increased on the trailing side but array heat transfer in downstream rows decreased.