Faculty Publications
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Item Effect of addition of aluminum nanoparticles on cooling performance and quench severity of water during immersion quenching(2012) Ramesh, G.; Prabhu, K.N.In the present work, the effect of the addition of aluminum nanoparticles in concentrations varying from 0.001 to 0.5 vol. % on the cooling performance and quench severity of water during immersion quenching is investigated. The results of cooling curve analyses show that an increase in nanoparticle concentration increased the cooling rates at critical temperatures up to 0.05 vol. % and decreased them thereafter. The transition from the vapor blanket stage to the nucleate boiling stage was also altered by quenching in nanofluids. A finite difference heat transfer program was employed to generate cooling curves at different values of heat transfer coefficient from thermo-physical properties of the quench probe material. A Grossmann H quench severity versus cooling rate curve was established, and from this curve, the H factors of prepared nanofluids were estimated. An increase in nanoparticle concentration up to 0.05 vol. %resulted in an increase of the H value of water from 63 m 1 to 93 m 1, and any further increase in the concentration of nanoparticles resulted in a decrease in H. The results suggest both the enhancement and the deterioration of the cooling performance of water by the addition of aluminum nanoparticles. Copyright © 2012 by ASTM International.Item Dimensionless cooling performance parameter for characterization of quench media(2013) Ramesh, G.; Prabhu, K.The effect of varying thermal properties and boundary heat transfer coefficients on temperature profiles inside cylindrical quench probes was simulated during immersion cooling. The results of simulation indicated that, for assessment of the cooling performance of the quench media, the ratio of the quench probe diameter to its thermal conductivity should be less than 0.0005 m2K/W. A simple dimensionless cooling parameter (D 2CR/??T) was proposed to assess the cooling performance of quench media. © 2013 The Minerals, Metals & Materials Society and ASM International.Item Effect of thermal conductivity and viscosity on cooling performance of liquid quench media(Maney Publishing Suite 1C, Joseph's Well, Hanover Walk Leeds LS3 1AB, 2014) Ramesh, G.; Prabhu, K.In this present work, the effect of the thermophysical properties of quenchants on its cooling performance was investigated. Water, brine solutions, polymer solutions and mineral oils were chosen to have quench media with varying thermophysical properties. Cooling curve analyses were carried out by using standard ISO/DIS 9950 quench probe. Grossmann H quench severity of the quench media was determined from the relation of H and cooling rate. Cooling curve analysis results showed that the change in thermophysical properties of the quench media had significant effect on the cooling history of the quench probe. The viscosity of the quenchant used for immersion quenching is the most important factor that controls the cooling performance of the quenchant compared to thermal conductivity of the quench medium. © 2014 IHTSE Partnership.Item Wetting and cooling performance of mineral oils for quench heat treatment of steels(Iron and Steel Institute of Japan, 2014) Ramesh, G.; Prabhu, K.In the present work, wetting kinetics, kinematics and heat transfer characteristics of mineral oils having varying thermo-physical properties sourced from different suppliers were investigated using contact angle, online video imaging and cooling curve analysis techniques. The relaxation behavior of mineral oils of low viscosity and surface tension on Inconel substrate indicated improved wettability and fast spreading kinetics while mineral oils of high viscosity and surface tension showed reduced wettability and slower spreading kinetics. Further, the spreading behavior of mineral oils of lower viscosity and density showed the absence of viscous regime. During rewetting, formation of double wetting fronts and more uniform nature of wetting front were observed with mineral oils of high viscosity and flash point whereas no additional wetting front was observed for mineral oils of low viscosity and flash point. Among the convectional/fast/hot mineral oils, higher wetting front velocity and cooling rate were obtained for low viscosity mineral oil. The heat extracting capability of high viscosity mineral oils was higher during vapour and nucleate boiling and lower during liquid cooling stage. Further, highly viscous mineral oils showed uniform heat transfer compared to mineral oils having low viscosity. © 2014 ISIJ.Item A dimensional parameter for prediction of cooling performance of quenchants(ASTM International, 2014) Prabhu, K.; Ramesh, G.Computer aided cooling curve analysis was carried out during immersion quenching of ISO/DIS 9950 quench probe. Water, brine solutions, polymer solutions, mineral oils, and vegetable oils were used as quench media. The results showed that the quench medium used had a significant effect on the quench probe cooling curve parameters. An empirical correlation was proposed to predict the average cooling rate from surface tension, wetting angle, thermal conductivity, and kinematic viscosity of the quench medium. © 2014 by ASTM International.Item Comparative study of wetting and cooling performance of polymer-salt hybrid quench medium with conventional quench media(Taylor and Francis Ltd., 2015) Ramesh, G.; Prabhu, K.Wetting kinetics, kinematics, and cooling performance of a polymer-salt hybrid quenchant were investigated. The rewetting phenomenon for brine, water, polymer, and polymer-salt hybrid solutions was characterized as rapid uniform, fast non-uniform, slow uniform, and fast uniform processes, respectively. A dimensionless rewetting time was proposed to assess the nature of the wetting front. The hybrid quenchant showed higher heat transfer during vapor and transition boiling and lower heat transfer during nucleate boiling and convective cooling. The presence of salt in the hybrid solution resulted in early destabilization of the vapor film and an increase in wetting front velocity and rewetting temperature. The polymer constituent delayed the rewetting phenomenon. © 2015 Taylor & Francis Group, LLC.Item Effect of Polymer Concentration on Wetting and Cooling Performance During Immersion Quenching(Springer Boston, 2016) Ramesh, G.; Prabhu, K.N.The effect of varying concentrations (0 to 100 vol pct) of glycol polymer solution on wetting kinetics, kinematics, and cooling performance during immersion quenching was studied by using goniometry, online video imaging, and cooling curve analysis techniques. An increase in concentration of the polymer solution resulted in improved wettability and accelerated spreading kinetics of the quench medium. The quench medium showed medium-fast-nonuniform, fast-uniform, slow-uniform, explosive/rapid, repeated, and slow-nonuniform rewetting phenomena depending on the concentration of the polymer solution. The collapse of the vapor film was by an instantaneous rupture process in the quench medium containing more water and by nucleation of bubbles caused by the selective rupture process in the quench medium enriched with polymer. The quench medium consisting of an equal amount of water and polymer showed an explosive collapse of the vapor film on the quench probe surface. The nature of the wetting front was uniform with polymer quench media except at 100 vol pct concentration of polymer quenchant. There was enhancement in the cooling performance of the quench medium, which was enhanced for a lower volume concentration of the polymer solution. However, an increase in the concentration of the polymer resulted in a decreased cooling performance. The cooling of the probe was more uniform with polymer quenchants (5 to 25 vol pct), which exhibited fast and uniform rewetting. Polymer quenchants (75 to 100 vol pct) that exhibited repeated and slow-nonuniform rewetting showed large variation in heat transfer over the quench probe surface. © 2015, The Minerals, Metals & Materials Society and ASM International.Item Wetting and Cooling Performance of Vegetable Oils during Quench Hardening(John Wiley and Sons Inc. P.O.Box 18667 Newark NJ 07191-8667, 2016) Ramesh, G.; Prabhu, K.N.Wetting kinetics, kinematics, and cooling performance of vegetable oils (sunflower, gingelly, palm, and coconut oils) during quenching of Inconel 600 probe were studied using goniometry, online video imaging, and cooling curve analysis. The results were compared with a conventional mineral oil quench medium. Improved wettability was obtained for vegetable oils with lower viscosity. Cooling curve analyses showed three stages of cooling for both mineral and vegetable oils. Video imaging of the quenching process and differential scanning calorimetry analysis confirmed that the first stage of cooling was caused by the formation of vapor film in mineral oil and due to the occurrence of a heated liquid layer around the quench probe surface in vegetable oils. Vegetable oils showed continuous boiling phenomenon during the convective cooling stage of quenching. The cooling performance of vegetable oils was found to depend on the concentration of mono-unsaturated fatty acid. The heat extracting capability of vegetable oils with lower mono-unsaturated fatty acid oils was found to be higher. However, no correlation was observed between fatty acid composition and uniformity of heat transfer. When compared to mineral oil quenching, vegetable oil quenching produced faster wetting kinematics and better cooling performance. © 2016 Wiley Periodicals, Inc.