Faculty Publications
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Item Wetting kinematics and spreading behaviour of water based aluminium nanofluids during immersion quenching(2013) Ramesh, G.; Prabhu, K.In the present work, wetting kinematics of water based aluminium nanofluids having nanoparticle concentrations varying from 0.001 to 0.5 vol.-% during immersion quenching of Inconel 600 probe was investigated by measuring the contact resistance. The contact resistance between the quench probe and counter electrode during quenching indicated that the duration of the film of water vapour decreased with increasing nanoparticle concentration as well as absence of stable vapour film formation with 0.05, 0.1 and 0.5 vol.-% of nanoparticles. The phenomenon of a repeated wetting process was observed during quenching in nanofluids. Further, quenching in 0.1 and 0.5 vol.-% nanofluids indicated the formation of a nanoparticle porous layer and its deposition on the quench probe. The spreading behaviour was studied by measuring the dynamic contact angle of nanofluids droplets on Inconel 600 substrate. Contact angle measurement showed that the addition of aluminium nanoparticles did not have a significant effect on the relaxation of contact angle of water droplet. However, lower static contact angles were obtained for nanofluids indicating improved wetting. © 2013 IHTSE Partnership.Item The effect of addition of copper nanoparticles on wetting behaviour of water during immersion quenching(2013) Ramesh, G.; Prabhu, K.In the present work, the effect of addition of copper nanoparticles to water, in concentrations varying from 0.001-0.1 vol%, on wetting behaviour during immersion quenching of Inconel 600 probe was assessed using near surface temperature probe and contact resistance methods. Quenching in nanofluids resulted in decreased duration of vapour blanket stage and rapid wetting. The wetting front velocity increases with increase in nanoparticle concentration. A stable vapour film was not formed during quenching in nanofluids of 0.05 and 0.1 vol%. Quenching in 0.01, 0.05 and 0.1 vol% nanofluids showed characteristics of repeated wetting process. Quenching in 0.1 vol% nanofluid resulted in the formation of porous layer of nanoparticles. © 2013 Indian Institute of Metals.Item The effect of load and addition of MWCNTs on silicone based TIMs on thermal contact heat transfer across Cu/Cu interface(Institute of Physics Publishing helen.craven@iop.org, 2019) Pathumudy, R.; Narayanprabhu, K.In the present work, the effect of thermal interface material (TIM) and load on contact heat transfer between hot and cold cylindrical copper specimens was assessed. Pristine silicone grease and multi walled carbon nanotubes (MWCNT) impregnated silicone grease was used as TIM. Copper specimens with L/D ratios of 1 and 5 were used. For copper specimens with L/D ratio of 1, the interfacial heat transfer was quantified by estimating the peak heat flux and integral heat flow using a lumped heat capacitance approach. An inverse solution to heat conduction equation was adopted for estimating heat flux transients for copper specimens with L/D ratio of 5. As the applied load increased from a no load condition to 5 kg, the peak heat flux and the corresponding integral flow increased significantly. Increasing the load above 5 kg did not result in any significant changes in the peak heat flux and integral heat flow for both sets of specimens. The effect of load on the contact heat transfer was significant in the absence of TIM. The use of 0.1 wt% MWCNT- silicone grease as TIM significantly increased the heat flow for no load condition. At higher loads, the effect of MWCNT was insignificant and caused deterioration in the heat flow parameters. Further, increasing the MWCNT content to 1 wt% in silicone grease decreased the heat flux transients at all loading conditions. The thermal contact resistance (RT) was calculated and it increased exponentially with the peak temperature difference (?Tmax) between hot and cold specimens irrespective of the L/D ratio. © 2019 IOP Publishing Ltd.Item Numerical investigation on the sensitivity of endplate design and gas diffusion material models in quantifying localized interface and bulk electrical resistance(Elsevier Ltd, 2021) Shinde, U.; Koorata, P.K.A localized non-intuitive relationship between electrical interface contact resistance and bulk properties such as bulk electrical resistance and permeability in the fuel cell gas diffusion layer (GDL) is reported. A numerical method is adopted to investigate contact pressure and hence the interface contact resistance at the interfaces of bipolar plate (BPP)|GDL and GDL|Polymer electrolyte membrane (PEM). The results are observed to be sensitive to GDL material models as well as endplate designs. This means, endplates designed to improve the electrical contact resistance or contact pressure at the BPP|GDL interface may not necessarily assure an improvement in bulk properties, in fact, it is observed in this study that these properties are inversely related. Further, a differential deformation in GDL along with consolidation effect is predicted with compressible version of hyperelastic material model. More importantly, it is revealed that the selection of material models plays a significant role in the deformation behaviour of the GDLs irrespective of the clamping design adopted. © 2021 Hydrogen Energy Publications LLCItem Numerical investigation on the effects of inhomogeneous gas diffusion layer and impact of interfacial contact resistance on the performance of polymer electrolyte fuel cells(Elsevier Ltd, 2024) Shinde, U.; Koorata, P.K.; Padavu, P.In this study, a three-dimensional single channel is numerically modeled to simulate the polymer electrolyte fuel cell (PEFC) with a homogeneous and inhomogeneous gas diffusion layer (GDL). The influence of interfacial contact resistance (ICR) between GDL and current collector ribs (GDL|CC) is also studied. In the present study, GDL is considered as a single component (homogeneous) in one case and inhomogeneous with varying electrical and flow properties to illustrate the inhomogeneity in another case. The inhomogeneity in GDL is primarily caused by localized deformation due to non-uniform contact pressure during fuel cell assemblies. The consideration of ICR is observed to have a significant effect on both the ohmic and mass transport regions of the polarization curve. Inhomogeneous GDL with ICR, considered close to a practical scenario, shows a ∼7% drop in performance evaluation at 0.3V. The study reveals increased consumption of reactants at higher current loads when ICR is assumed negligible. This study examines the effects of homogeneous GDL, inhomogeneous GDL, and the impact of ICR on the distributions of reactant concentration, water concentration, temperature, current density, and polarization curve in PEFC. This study presents the practical aspects of PEFC considering inhomogeneous GDL electrical and flow properties. © 2023 Hydrogen Energy Publications LLC