Faculty Publications
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Item Reprocessed waste sunflower cooking oil as quenchant for heat treatment(Elsevier Ltd, 2020) Prathviraj, M.P.; Samuel, A.; Prabhu, K.N.The growing concern to minimize the use of petroleum derived mineral oil in heat treatment industries has led to the search for alternative eco-friendly quenchants. Although vegetable oils seem to be a viable option, the higher cost and inferior thermal and oxidation stability have limited their application in the heat treatment industry. The reuse of waste cooking oils for industrial heat treatment would not only make quenchants cost-efficient but also environment friendly. In this study, the cooling performance of waste sunflower cooking oil was assessed and compared with that of unused sunflower cooking and mineral oils. The waste sunflower oil was made suitable for quenching by cleaning and chemical treatment. The experiment to assess the suitability of reprocessed oil for quenching was conducted using an Inconel 600 standard probe according to ISO 9950 and ASTM D 6200 standards. The thermal history acquired while quenching of the probe was used to estimate the surface heat flux transients. The results indicated that the chemically treated waste sunflower cooking oil had a higher cooling performance than that of unused sunflower and the mineral oils. A good agreement was found between the heat flux transients and hardness data obtained with the quenched AISI 4140 steel probe. The simulation of temperature and hardness distribution indicated more uniformity along the length of the probe indicating more uniform cooling with chemically treated waste sunflower cooking oil. © 2020 Elsevier LtdItem Experimental investigation of heat transfer characteristics of polyethylene glycol (PEG) based quench media for industrial heat treatment(Elsevier Inc., 2023) Soni, A.; Samuel, A.; Prabhu, K.Aqueous polymer quenchants are now increasingly used in the quench hardening of steels. The inverse solubility property of polymer media leads to polymer film encapsulation of the quenched component, followed by an instantaneous rupture of the polymer film. The film boiling stage is absent, thus improving heat transfer uniformity. In the present investigation, the effect of molecular weight of Polyethylene glycol (PEG) on heat transfer characteristics of PEG/water quenchants with concentrations of 5, 10, and 20 vol% was studied. The cooling curve analysis is performed to assess the cooling characteristics. Spatially dependent surface heat flux transients are estimated using the inverse heat conduction method. The rewetting kinematics is analyzed by videography and acoustic analysis of polymer film rupture during quenching. The results indicated that an increase in the molecular weight of PEG from 200 to 6000 changed the rewetting kinematics from a local wetting front movement to an instantaneous rupture of the polymer film. The change in the rewetting kinematics is reflected in the surface heat flux, indicating an increased uniformity of heat transfer. The film rupture acoustics showed that the polymer film's instantaneous breakup had a higher sound intensity than the one showing wetting front motion. © 2023 Elsevier Inc.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.