Impacts of Pin Fin Shape and Spacing on Heat Transfer and Pressure Losses

Additive manufacturing (AM) provides designers with the freedom to implement many designs that previously would have been costly or difficult to traditionally manufacture. This experimental study leverages this freedom and evaluates several different pin shapes integrated into pin fin arrays of a variety of spacings. Test coupons were manufactured out of Hastelloy-X using direct metal laser sintering and manufacturer-recommended process parameters. After manufacturing, internal surface roughness and as-built accuracy were quantified using Computed Tomography (CT) scans. Results indicated that pin fins were all moderately undersized, and there was significant surface roughness on all interior surfaces. Experimental data indicated that diamond-shaped pins were found to have the highest heat transfer of the tested shapes, but triangle-shaped pins pointed into the flow incurred the smallest pressure drop. Modifications to the streamwise spacing of the pins had little impact on the friction factor, but did increase heat transfer with increasing pin density. Prior Nusselt number correlations found in literature underestimated heat transfer and pressure loss relative to what was measured resulting from the AM roughness. A new correlation was developed accounting for AM roughness on pin fin arrays.