Design and Testing of a Jet-Impingement Instrument to Study Surface-Modification Effects by Nanofluids

The growing research interest on nanofluids, the suspensions of nano-size powders in ordinary fluids with enhanced cooling properties, has led the authors to study surface modifications (i.e., possible erosion-corrosion effects) from nanofluid interactions with typical heat-exchanger materials. This article discusses existing instruments and the rationale for designing a new ad-hoc test rig using jet-impingement at speeds from 3.5 m/s to 35 m/s. Preliminary tests used typical nanofluids—2% volume alumina-nanopowder in water—which were jet-impinged at 15.5 m/s speed on aluminum and copper specimens. The instrument, methodologies and assessment tools proved to be appropriate to test for the nanofluid interactions with material surfaces. The studied surface modifications, which were assessed by roughness measurements, weighing for removed-material, and optical-microscopy, suggest that addition of nano-powders can lead to patterns of erosion-corrosion that are substantially different than those typically obtained from base fluids.