Conference Papers

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    Inverse modeling of heat transfer with application to solidification and quenching
    (2002) Prabhu, K.N.; Ashish, A.A.
    The inverse modeling of heat transfer involves the estimation of boundary conditions from the knowledge of thermal history inside a heat conducting body. Inverse analysis is extremely useful in modeling of contact heat transfer at interfaces of engineering surface during materials processing. In the present work, the one-dimensional transient heat conduction equation was inversely modeled in both cartesian as well as cylindrical coordinates. The model is capable of estimating heat flux transients, chill surface temperature, and total heat flow from the source to the sink for an input of thermal history inside the sink. The methodology was adopted to solve boundary heat transfer problems inversely during solidification and quenching. The response of the inverse solution to measured sensor data was studied by carrying out numerical experiments involving the use of varying grid size and time steps, future temperatures, and regularization techniques.
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    Experimental models for assessment of interfacial heat transfer in dip soldering
    (2010) Nyamannavar, S.; Prabhu, K.N.
    The success of a numerical simulation for solder solidification during soldering processes depends on an accurate knowledge of heat transfer phenomenon at the solder/substrate interface. Two experimental setups were designed to study the interfacial heat transfer at solder/substrate interface. In the first method, a cylindrical probe of substrate material was dipped in liquid solder and solder was allowed to solidify around the metal probe. In the second method the test probe was dipped in the bulk solder liquid of sufficiently large quantity and allowed to attain the surrounding solder liquid temperature. Temperature at the center of the probe was measured using thermocouple. Heat flux transients at the surface of the probe were estimated by lumped heat capacitance method. SEM study at the solder/substrate interfacial region for experiments of solidifying solder around the test probe revealed the existence of a clear gap with aluminum substrate. A conforming contact was obtained with copper substrate. The nature of heat flux transients was found to be different in two experiments. © (2010) Trans Tech Publications.
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    Assessment of heat transfer during solidification of Al-22% Si alloy by inverse analysis and surface roughness based predictive model
    (Springer India sanjiv.goswami@springer.co.in, 2012) Jayananda; Prabhu, K.N.
    Heat flux transients were estimated during unidirectional downward solidification of Al-22% Si alloy against copper, die steel and stainless steel chills. The chill instrumented with thermocouples was brought into contact with the liquid metal so as to avoid the effect of convection associated with the pouring of liquid metal. Heat flux transients were estimated by solving the inverse heat conduction problem. Higher thermal conductivity of chill material resulted in increased peak heat flux at the metal/ chill interface. Peak heat flux decreased when 100 lm thick alumina coating was applied on the chill surface. The lower thermal conductivity of alumina based coating and the presence of additional thermal resistance decreases the interfacial heat transfer. For uncoated chills, the ratio of the surface roughness (R a) of the casting to chill decreased from 6.5 to 0.5 with decrease in the thermal conductivity of the chill material. However when coating was applied on the chill, the surface roughness ratio was nearly constant at about 0.2 for all chill materials. The measured roughness data was used in a sum surface roughness model to estimate the heat transfer coefficient. The results of the model are in reasonable agreement with experimentally determined heat-transfer coefficients for coated chills.
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    Estimation of interfacial heat transfer coefficient for horizontal directional solidification of Sn-5wt%pb alloy using genetic algorithm as inverse method
    (Springer Verlag, 2019) Vishweshwara, P.S.; Gnanasekaran, N.; Arun, M.
    In the present work, a one-dimensional transient solidification heat transfer problem is solved to determine the unknown interfacial heat transfer coefficient (IHTC) at the mold–metal interface using genetic algorithm (GA), an evolutionary and widely known algorithm, as an inverse method. The forward model is numerically solved to obtain the exact temperatures by incorporating the appropriate correlation for the IHTC that varies with time. In order to mimic experiments, the exact temperatures are then perturbed with the standard deviations of 0.01, 0.02, and 0.03. In the inverse estimation, genetic algorithm is used to minimize the objective function, thereby reducing the error between the measured and the simulated temperatures. The study on the performance parameters of the algorithm is also discussed in detail. © Springer Nature Singapore Pte Ltd. 2019.
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    A novel framework for the estimation of interfacial heat transfer coefficient using Bat algorithm during solidification of metal casting
    (Toronto Metropolitan University, 2019) Vishweshwara, P.S.; Gnanasekaran, N.; Arun, M.
    In the present work, the interfacial heat transfer coefficient (IHTC) at the mold metal interface is estimated during solidification of Al-4.5wt%Cu alloy using ANN-Bat-Bayesian framework. The forward model comprises of a one dimensional transient governing equation for the solidification of metal casting and is solved using explicit finite difference scheme with the available IHTC correlation from the literature. Within the range of values of constants of IHTC correlation, a set of numerical simulation is performed and corresponding temperature output is trained using Artificial Neural Network (ANN). The network created acts a fast forward model replacing the FDM scheme during IHTC estimation thus reducing computational time. Bat algorithm is used as inverse method along with the Bayesian framework, that drives towards the accurate retrieval of unknown parameters. © 2019, Toronto Metropolitan University. All rights reserved.