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.

Development and Assessment of a New Flow-Through Test Instrument to Study Wear and Erosion Effects of Nanofluids

Nanofluids, the suspensions of nano-size powders in ordinary fluids, are of technical interest for their enhanced cooling properties, but their possible erosion-corrosion effects on cooling-system materials are mostly unknown. This paper discusses the rationale for designing and developing a new test-rig with flow-through parallel to the tested surfaces. The instrument conduct-chamber accommodates multiple specimens for simultaneous testing, and controlled fluid speed and temperature. This study shows that the new rig yields measurable surface-modifications from nanofluid action in reasonable test-times. Results are presented for a nanofluid (of 2%-alumina-nanopowder in water) that is recirculated in parallel-flow contact with polished aluminum and copper. Surface modifications are assessed by roughness, weighing of removed-material, and optical-microscopy, and results indicate that nanopowders can lead to patterns of wear, erosion and corrosion that are substantially different than those typically obtained from the base-fluids.