Faculty Publications
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Publications by NITK Faculty
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Item Wetting Behavior and Heat Transfer of Aqueous Graphene Nanofluids(Springer New York LLC barbara.b.bertram@gsk.com, 2016) Nayak, U.V.; Prabhu, K.N.Aqueous graphene nanofluids having concentrations 0.01, 0.1, and 0.3 vol.% were used as heat transfer media during quenching of ISO 9950 inconel alloy probe. Contact angle measurements were carried out to assess the wettability of graphene nanofluids. Nanofluids showed better wettability compared to base water with over 16% reduction in their contact angles. The cooling performance of the quench media was assessed by cooling curve analysis during quenching of an instrumented inconel probe from 860 °C into the quench medium. Recorded temperature readings showed longer vapor phase stage during quenching with nanofluids. The severity of nanofluids was found to be lower relative to water. During quenching with nanofluids, the estimated spatiotemporal heat flux transients at the metal/quenchant interface showed that more heat was removed during the vapor phase stage of cooling. The present study brings out the possibility of using stable water-graphene nanoplatelet suspensions for quench heat treatment of steel components requiring cooling severity between water and oil/polymer quenchants. © 2016, ASM International.Item Assessment of spatiotemporal heat flux during quenching in TiO2 and AlN nanofluids(ASTM International, 2017) Nayak, U.V.; Ramesh, G.; Prabhu, K.N.In the present work, spatiotemporal heat flux transients were estimated during quenching of an Inconel 600 alloy probe in water-based titanium dioxide (TiO2) and aluminum nitride (AlN) nanofluids that have nanoparticle concentrations varying from 0.001 to 0.5 vol. %. The results showed reduced peak heat flux and a longer vapor phase stage during quenching with nanofluids compared to quenching with water. The peak heat flux for quenching in nanofluids was lowered with increase in the nanoparticle concentration. Quenching with TiO2 nanofluids resulted in slower heat extraction compared to quenching in AlN nanofluids at higher concentrations. Quenching with nanofluids resulted in a more uniform quench compared to quenching with water because of the reduction in the rewetting period. © © 2017 by ASTM International.Item Quench cooling performance-hardness correlation for AISI 1045 and 1090 steels(ASTM International, 2019) Nayak, U.V.; Prabhu, N.Heat transfer and microstructure evolution during quenching of AISI 1045 and 1090 steels in vegetable oils was investigated. To simulate the industrial quench heat treatment, reference probes made of medium and high carbon steels were quenched, and heat flux transients were estimated by taking into account the phase transformation. The cooling curves obtained with reference probes made from AISI 1045 and AISI 1090 steels showed kinks indicating enthalpy change accompanied with phase transformations during continuous cooling. This was reflected in the estimated heat flux curves. The section thickness effect on heat flux transients was examined by using probes of diameters 25 mm and 50 mm. The cooling rates measured at various locations across the section diameter of reference probes were related to the hardness using the quench factor technique. The heat transfer characteristics of the quench media, the evolved microstructure, and the resulting hardness were in complete agreement. © 2019 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959.