Experimental friction factors on cooling channels made via additive manufacturing at different building orientations

Metal powder Additive Manufacturing (AM) technology is an innovative process that has recently been proposed to improve the efficiency in heat transfer and cooling applications. In cooling channels made via laser powder bed fusion, pressure drop can become a critical issue because of the high surface roughness in as-built objects. In this work, the influence of surface roughness on pressure drops along straight channels, generated by different AM building orientations is studied. Five different sloping angles have been investigated in CuCrZr channels samples with a square cross-section: 0° (horizontal), 45°, 60°, 75° and 90° (vertical). In the same AM process, an inclined wall for each different sample was manufactured. A surface texture analysis was carried out on both sides of each wall. In the meantime, X-ray computed tomography was employed to measure the cross-sections and the hydraulic diameters of each channel. The five channels were experimentally tested, measuring the pressure drops varying water flow at different Reynolds numbers, in the transitional and turbulent flow regimes. As proposed by Favero et al. [1], the experimental friction factor was used to compute a mean absolute roughness for each building orientation channel, by taking Moody’s diagram for rough pipes as reference.