Heat transfer and flow structure characterization for pin fins produced by cold spray additive manufacturing

Abstract

The focus of this work is the characterization of the thermal and hydraulic performance of pin fin arrays produced using the cold spray additive manufacturing process. The heat transfer and the pressure losses of 1mm high round base, square base and diamond base tapered pin fin arrays were assessed in both the inline and staggered configurations for fin densities of 8fpi and 12fpi. These performances were correlated to the turbulence intensity and the turbulent kinetic energy values at various locations in the flow, measured by micro-particle image velocimetry. It was inferred that the form drag is the main contributor to the pressure loss and was found to correlate with the flow turbulent kinetic energy in the fin wake. In contrast, the convective heat transfer coefficient correlated better with the turbulence intensity, leading to the conclusion that heat transfer is not dictated solely by the turbulent kinetic energy, but by the relative strength of the velocity fluctuations with respect to the average flow velocity at the same location. Furthermore, the flow structures for the different fin array samples were visualized and are discussed. Finally, it was found that although the samples had very varied thermal and hydrodynamic performances as a function of Reynolds number, the different samples at a given fin density had similar thermal conductances at a given pumping power.