Faculty Publications
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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.Item Assessment of Heat Transfer Characteristics of Transesterified Waste Sunflower Cooking Oil Blends for Quench Hardening(Springer, 2022) Samuel, A.; Prabhu, K.N.Mineral oils used in the heat treatment industry are derivatives of non-renewable petroleum fuel and are toxic and non-biodegradable. Vegetable oils are an ideal substitute for mineral oil due to their superior heat transfer characteristics and eco-friendliness. However, the initial cost of vegetable oils is very high. In addition, the maintenance cost of vegetable oils would be higher due to their poor thermal and oxidative stability than mineral oil. In this context, recycling and reusing waste cooking oil could be a cheaper and eco-friendly alternative. In this study, the fatty acid methyl ester (FAME) produced from the waste sunflower cooking oil through transesterification was blended with sunflower and mineral oils at various proportions. The cooling characteristics of the FAME/oil blends were assessed using the cooling curve analysis according to ASTM D6200 and ISO9950 standards. A solution to the inverse heat conduction problem was used to estimate the spatiotemporal metal/quenchant interfacial heat flux. The uniformity of heat flux was analyzed. The results indicated that blending waste cooking oil-derived FAME in sunflower oil up to 60 vol.% and mineral oil up to 50 vol.% provided comparable cooling characteristics to pure oils. The estimated heat flux transients showed a marginal decrease in peak heat flux for FAME blends in sunflower oil, whereas an increased peak heat flux with mineral oil. The FAME blends less than 60 vol.% in sunflower oil showed higher cooling uniformity. With mineral oil, the blend proportion of up to 50 vol.% increased cooling uniformities compared to pure oil. The characteristic cooling time (t85) increased with the increase in FAME blends in oils. However, the distribution of t85 in the quench probe was uniform for FAME/oil blends. © 2022, ASM International.Item The Effect of Thermal Quench Cycling on the Stability and Heat Transfer Characteristics of Transesterified-Epoxidized Used Cooking Oil Blended Quench Medium(Springer, 2024) Samuel, A.; Prabhu, K.N.Mineral oil is a widely used quench media in the heat treatment industries. They are derived from petroleum crude oil, and are toxic, and non-biodegradable. Therefore, in order to minimize the use of mineral oil, the fatty acid methyl esters (FAME) derived from the used cooking oil through the transesterification process can be blended with mineral oil. However, due to the high amount of unsaturation, blending of FAME in mineral oil would decrease the thermal-oxidative stability of the oil. Therefore, in the present work, to improve the stability of the mineral/FAME blend quenchant, the unsaturation in the FAME is decreased through epoxidation. The stability of epoxidized FAME/mineral blended oil is assessed by thermogravimetric analysis and thermal quench cycling. The quench cycles were performed using an ISO 9950 Inconel 600 standard probe. The viscosity and cooling performance of the oil were assessed periodically after the 1st, 10th, 50th, and 100th quench cycle. Investigation of cooling performance was performed by carrying out cooling curve analysis and estimating metal/quenchant interfacial heat flux tranisents. The results indicated that the thermal stability of the blend quenchant was improved with the epoxidation of FAME. The relative increase in viscosity was lower for blend quenchants than that for the mineral oil. The epoxidized FAME/mineral oil blend showed comparable cooling performance as that of mineral oil as the number of quench cycles were increased. © ASM International 2023.