Nanofluids are nanosize-powder suspensions that are of interest for their enhanced thermal transport properties.They are studied as\npromising alternatives to ordinary cooling fluids, but the tribiological effects of nanofluids on cooling-system materials are largely\nunknown. The authors have developed methodology that uses jet impingement on typical cooling-system materials to test such\neffects.Thework is presented of the authors� research on the interactions of a typical nanofluid (2% volume of alumina nanopowders\nin a solution of ethylene glycol in water) which is impinged on aluminum and copper specimens for tests as long as 112 hours. The\nsurface changes were assessed by roughness measurements and optical-microscope studies. Comparative roughness indicate that\nboth the reference cooling fluid of ethylene glycol and water and its nanofluid with 2% alumina produce roughness changes in\naluminum (even for the shortest 3-hour test), but no significant roughness differences were observed between them. No significant\nroughness changes were observed for copper. Microscopy observations, however, show different surface modifications in both\naluminum and copper by both the nanofluid and its base fluid. The possible mechanisms of early erosion are discussed. These\ninvestigations demonstrate suitable methods for the testing of nanofluid effects on cooling system-materials.
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