Assessment of the Wear Effects of Alumina-Nanofluids on Heat-Exchanger Materials

Nanofluids are nano-size-powder suspensions in liquids that are mainly studied for their abnormal thermal transport properties, and hence as enhanced alternatives to ordinary cooling fluids. The tribological effects of nanofluids are, however, largely unknown, in particular their likely wear and/or erosion effects, because of their interaction with cooling-system (heat-exchanger) materials. The thesis presents research to establish methodologies for testing and evaluating surface-change by nanofluid impact. The work is presented on development of novel test rigs and testing methodologies, and on the use of typical surface analysis tools for assessment of wear and erosion that may be produced by nanofluids; prediction of such effects in cooling systems is discussed. Two new tests rigs were designed and developed: a multiple nozzle test rig and a parallel flow test rig. A main purpose of this research work was to assess the use of these new test rigs to evaluate nanofluid wear, and the ad-hoc newly proposed testing methodologies are discussed. Experimental results are presented on typical nanofluids (as 2%-volume of alumina nanopowders in 50/50 water/ethylene glycol solution, and in distilled water) which are jet-impinged (on aluminum and copper specimens) with 3.5 m/s to 15.5 m/s jet-speeds and in a 1 m/s parallel-flow (along the test specimen surface) during long test periods. The obtained surface modifications were assessed by roughness measurements, by weighing of removed-material, and by optical-microscopy. The results are presented on the observed substantially different surface modifications when same tests are conducted in aluminum and copper, and by both the base fluids and its alumina-nanofluids. The likely mechanisms of early erosion and abrasion, and the possibility of extrapolating the test-rig results and methodologies to typical cooling systems are discussed

Jet-Impingement Effects of Alumina-Nanofluid on Aluminum and Copper

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

Erosion-Corrosion Wear of Heat-Exchanger Materials by Water/ethylene-Glycol/alumina Nanofluids

Nanofluids are suspensions of nanoparticles in ordinary coolants, but their tribological effects on heat-exchanger materials are unknown. Previous research has explored wear from distilled-water-base nanofluids only, while most engine-coolants are alcohol solutions in water. This article presents testing of aluminum and copper by jet impingement of 50%-ethylene-glycol in water solution and of its 2%-alumina nanofluid. The effects are investigated of nanoparticle addition on the anticorrosion protection provided by ethylene glycol. The observed modifications showed that ethylene-glycol in water nanofluid led to wear patterns that were different than those obtained with the base-fluid; nanoalumina addition enhanced erosion and corrosion on aluminum and copper. Comparing the effects of ethylene glycol and its nanofluid solutions to those from same tests performed with distilled-water and its nanofluid suggests that nanopowders can substantially enhance wear by decreasing the anticorrosion action of ethylene glycol by a synergetic mechanism of erosion-corrosion

Testing of Wear and Erosion Effects of Nanofluids on Metals: New Instruments and Assessment Methodologies

This paper was published in the STLE Annual Meeting and Conference 2018

Assessment of Surface Modifications from Interactions of Alumina-Nanofluids on Heat-Exchanger Materials

This paper was published in the STLE-Tribology Frontiers Conference

Design and Development of Novel Test Instruments to Assess Tribological Effects of Nanofluids

This paper was published in the STLE Annual Meeting and Conference 2016

Effect of Ply Stacking Sequence on Structural Response of Symmetric Composite Laminates

In this work, the effect of ply stacking sequence on the structural response of multi-ply unidirectional fiber-reinforced composite laminates was evaluated using finite element analysis. The objective of this study was to develop a computational model to analyze the stress response of individual plies in a composite laminate for a given stacking sequence. A laminated composite plate structure under tensile loading was modeled in ANSYS. Stress profiles of the individual plies were obtained for each lamina. An Epoxy matrix with both unidirectional Graphite and Kevlar fibers was considered for the model. Three dimensional sectioned shell elements (SHELL181) were used for meshing the model. Several sets of stacking sequences were implemented, symmetrical to the mid-plane of the laminate. Symmetric stacking configurations of 6 layers stacked in ply angles of [0/45/-45]s, [0/60/-60]s, [0/45/90]s, and an 8-layered arrangement of [0/45/60/90]s were modeled for the analysis. The layer thickness was maintained at 0.1 mm. The results were compared against an analytical model based on the generalized Hooke’s law for orthotropic materials and classical laminate theory. A numerical formulation of the analytical model was implemented in MATLAB to evaluate the constitutive equations for each lamina. The stress distributions obtained using finite element analysis have shown good agreement with the analytical models in some of the cases

Wear Effects Assessment of Alumina Nanofluids in a Through-Flow Test-Rig

This paper was published in the STLE Annual Meeting and Conference 2017