Faculty Publications
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Item Assessment of wetting kinematics and cooling performance of select vegetable oils and mineral-vegetable oil blend quench media(Trans Tech Publications Ltd ttp@transtec.ch, 2015) Pranesh Rao, K.M.; Prabhu, K.Quench hardening is a process where an alloy is heated to solutionizing temperature and held for a definite period, and then rapidly cooled in a quenching medium. Selection of quenchant that can yield desired properties is essential as it governs heat extraction process during quenching. In the present work, the cooling performance of vegetable oil and mineral-vegetable oil blend quench media was assessed. The vegetable oils used in this work were olive oil, canola oil and rice bran oil. The mineral-vegetable oil blends were prepared by blending 10 and 20 vol. % of rice bran and canola oil in mineral oil. Inconel probe of 12.5mm diameter and 60mm height, instrumented with thermocouples were used to characterize quenchants. The probe was heated to 850°C and quenched in the oil medium. The cooling curves at different locations in the probe were used to study wetting kinematics. Inverse modelling technique was used to estimate spatially dependent metal-quenchant interfacial heat flux. It was found that the vegetable oils exhibited very short vapour blanket stage compared to mineral oil and blends. Faster wetting kinematics obtained with blends resulted in uniform heat transfer compared to that of mineral oil. The temperature distribution in the probe quenched in vegetable oils and blends was more uniform compared to that in mineral oil. It is expected that the parts quenched in vegetable oils and blends would lead to better hardness distribution compared to mineral oils. © (2015) Trans Tech Publications, Switzerland.Item Heat transfer during immersion quenching in MWCNT nanofluids(Trans Tech Publications Ltd ttp@transtec.ch, 2015) Nayak, U.; Prabhu, K.Quench heat treatment consists of rapid cooling of steel alloys after austenetization by subjecting them to cooling in a suitable cooling medium. At the heart of quench treatment is the transient heat transfer that occurs between the metal surface and the quenchant at their interface. This governs the quality of the component as it influences phase transformation, residual quench stresses and mechanical properties developed. In the present research work, spatially dependent transient heat flux in the axial direction was estimated using cooling curve analyses coupled with inverse heat conduction technique. A standard Inconel 600 probe instrumented with multiple thermocouples and heated to 865°C was quenched in distilled water (DW) and DW based multi walled carbon nanotubes (MWCNT) quench media. For evaluating the cooling performance, nanoquenchants with concentrations of 0.01, 0.1 and 1.0g/lt. were prepared. The cooling rate curve calculated from the measured temperature at the geometric center of the probe and the estimation of spatially dependent heat fluxes showed that the heat extraction during quenching with MWCNT nanoquenchant (0.1g/lt.) was higher than the other quenchants. The measured values of thermal conductivity and viscosities of quenchants did not show any significant variation. © (2015) Trans Tech Publications, Switzerland.Item Synergestic approach for the simultaneous estimation of heat transfer coefficient and heat flux using fin from steady state heat transfer experiments(Begell House Inc., 2015) Kumar, H.; Kumar, S.; Srinivasa Sagar, K.; Gnanasekaran, N.This paper reports simultaneous estimation of heat transfer coefficient and heat flux from natural convection fin heat transfer. The experimental setup contains rectangular mild steel fin of dimensions (250×154×6 mm) and an aluminium base plate of dimensions (250×150×8 mm). A slot of 4mm depth is created at the center of aluminium plate along its length (250mm) and mild steel fin is press fitted into this slot. Eighteen calibrated K-type thermocouples are used to record the temperature of the base plate and the fin. Beneath the base plate, a heater is placed with the dimensions of the base plate. To restrict the heat loss, bottom and sides of the heater are insulated with glass wool. Steady state experiments are carried out for different heat input. The problem considered is an inverse problem where in heat transfer coefficient and heat flux can be estimated simultaneously for the given temperature data from experiments/surrogate data. The forward model uses Asymptotic Computational Fluid Dynamics (ACFD) to obtain temperature distribution for the assumed inputs (heat transfer coefficient and heat flux). A powerful Markov Chain Monte Carlo method along with Metropolis-Hastings algorithm is used to minimize the objective function. Finally, the estimated values of heat transfer coefficient and heat flux are reported in terms of mean. © 2021, Begell House Inc. All rights reserved.Item Effect of thermal response on physical properties during drilling operations-A case study(Elsevier Ltd, 2018) Vijay Kumar, S.; Murthy, Ch.S.N.; Kunar, B.M.The temperature induced or generated during deep hole drilling operations is due to the heat generated between the interface of work piece surface and the tool surface. Several research study have been conducted to predict the temperature involved while drilling process as a predominant functions of many parameters like feed rate, torque, depth of cut etc. Similarly many experimental procedures have been conducted by several researchers to measure temperature directly by using thermocouples, infrared measurement, pyrometer, and thermisters etc. There is no precise experimental method is available to measure analytical value of energy, power, heat flux etc, while drilling process. The temperature rigma depends on material compositions and physical properties. This paper presents the influence of temperature on physical properties of some study samples during drilling operations. © 2017 Elsevier Ltd.Item MCMC and approximation error model for the simultaneous estimation of heat flux and heat transfer coefficient using heat transfer experiments(Begell House Inc., 2018) Gnanasekaran, N.; Kumar, M.K.; Balaji, C.This work deals with the simultaneous estimation of the heat flux and the heat transfer coefficient from a mild steel fin losing heat to the ambient by natural convection. Steady state heat transfer experiments are performed on a mild steel fin of dimension 150x250x6 (all dimensions are in mm) placed on to an aluminum base plate of dimension 150x250x8 (all dimensions are in mm). The experimental set up is placed inside a large enclosure to avoid natural disturbances. Nine calibrated K-type thermocouples are used to measure the temperatures of the fin and the base plate. The forward solution of a three dimensional conjugate heat transfer fin model is solved using commercially available ANSYS software in order to obtain the temperature distribution of the fin. An inverse problem is proposed for the estimation of unknown parameters within the Bayesian framework of statistics. Furthermore, a model reduction in the form of Approximation Error Model (AEM) is considered for the inverse conjugate natural convection heat transfer problem. Such an approach not only mitigates the complexity of the inverse problem but also compensates the model reduction with all necessary statistical parameters. Additionally, the sample space within the Bayesian framework is explored with the help of Markov Chain Monte Carlo Method (MCMC) along with the Metropolis-Hastings algorithm. The results of the inverse estimation using Approximation Error Model based on the experimental temperature prove to be a promising alternative in inverse conjugate heat transfer problems. © 2018 International Heat Transfer Conference. All rights reserved.Item LBM combined with LM algorithm to estimate the unknown heat flux - A new inverse approach(Elsevier Ltd, 2019) Kumar, D.; Arumuga Perumal, D.A.; Gnanasekaran, N.; Kumar, M.K.The objective of the present work is the application of the Levenberg-Marquardt method as an inverse method for the estimation of the heat flux. In this paper inverse estimation of heat flux for a two-dimensional heat conduction problem is carried out. As a direct method, in the first attempt the solution of two-dimensional inverse heat conduction problem is formulated by using Lattice Boltzmann Method as a forward model. Later the solution to the problem is also obtained by using Finite Difference Method (FDM) as the forward model for the purpose of validation. Once the forward model is established, Levenberg-Marquardt Method is used as an inverse model to estimate the input parameter i.e. heat flux which is reported. A complete error analysis of inverse model with known values is performed. As the Lattice Boltzmann Method (LBM) is acclimatizing to parallel computation, its use is recommended in Levenberg-Marquardt method for the solution of inverse heat conduction problem which is evident from the results. © 2019 Elsevier Ltd.Item Estimation of Heat Flux Transient During Quench Hardening of Varying Diameter Steel Probes Using IHCP-Phase Transformation Coupled Model(ASM International, 2023) Samuel, A.; Nayak, U.V.; Pranesh Rao, K.M.P.; Prabhu, K.N.The phase transformation model is coupled with the inverse heat conduction problem (IHCP) to estimate the steel/quenchant interfacial heat flux. Cylindrical steel probes having section thicknesses 25 and 50mm, respectively, and lengths 30mm were made from medium and high carbon steels (AISI 1045 and 52100). The probes were quenched in mineral, neem, and sunflower oils. The cooling curves at the centre and near the surface of steel probes were recorded. The near-surface cooling curve was used as a reference temperature data in the IHCP algorithm for the estimation of surface heat flux, whereas the cooling curve at the centre was used as the boundary condition of the axisymmetric model of the probe. The effect of phase transformation on the metal/quenchant interfacial heat flux was indicated by a kink and rise of heat flux. The increase in the section thickness of the probe from 25 to 50mm decreased the magnitude of the heat flux. Increasing section thickness increases the phase transformation, increasing the resistance to heat flow at the metal/quenchant interface. © © 2023 ASM International®Item Item Heat transfer at the metal/chill interface during solidification of commercially pure aluminium square bar castings with cast iron chill at one end was investigated. Experiments were carried out for different chill thicknesses and superheats. The inner surface temperature of the chill initially was found to increase at a faster rate for higher superheats. The effect of chill thickness on the inner surface temperature of the chill was observed only after the heat from the solidifying casting had sufficient time to diffuse to the interior of the chill material. Inverse analysis of the non-linear one-dimensional Fourier heat conduction equation indicated the occurrence of peak heat flux at the end of filling of the mould. The effect of superheat on heat flux was minimal after filling. However, the effect of chill thickness had a significant effect on the heat flux after the occurrence of peak heat flux. Higher heat flux transients were estimated for castings poured at higher superheats. The corresponding heat transfer coefficients were also estimated and reported. The heat flux model presented in this work can be used for determination of casting/chill interfacial heat flux as a function of chill thickness and superheat. These heat flux transients could be used as boundary conditions during numerical simulation of solidification of the casting. © 2002 Elsevier Science B.V. All rights reserved.(Effect of chill thickness and superheat on casting/chill interfacial heat transfer during solidification of commercially pure aluminium) Gafur, M.A.; Haque, M.N.; Prabhu, K.2003