Faculty Publications
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Item Physico-chemical, acoustic and excess properties of glycylglycine-MnCl2 in aqueous ethanol mixtures at different temperatures(2010) Santosh, M.S.; Bhatt, A.S.; Bhat, D.K.Volumetric, acoustic, refractometric, excess and deviation properties of glycylglycine-MnCl2 in aqueous ethanol mixtures have been reported at T = (288.15 to 318.15) K. Redlich-Kister equation was used to fit the derivate properties. The experimental data of the constituent binaries were analyzed to discuss the nature and strengths of intermolecular interactions. The interdependence of Lf and u has been evolved from Eyring and Kincaid model. The variations in specific acoustic impedance revealed that hydrogen bonding was predominant in the studied binary mixtures. Solvation number indicated structure-breaking tendency of the solute and weakening of local solvent structure. © 2010 Elsevier B.V. All rights reserved.Item Excess molar volumes, viscosity deviations and isentropic compressibility changes in glycylglycine-NiCl2 aqueous ethanol mixtures(2010) Santosh, M.S.; Bhat, D.K.The densities, viscosities and ultrasonic velocities for glycylglycine-NiCl2 in aqueous ethanol mixtures have been studied in the temperature range 288.15-318.15K. The excess molar volumes, viscosity deviations and changes in isentropic compressibility for the binary mixtures have been calculated and discussed in terms of hydrogen bonding and structure-breaking effect. The computed results are fitted to the Redlich-Kister polynomial. The results clearly indicate that there is a strong association in the mixtures studied. © 2010 Elsevier B.V.Item Nucleate pool boiling heat transfer measurement and flow visualization for ammonia-water mixture(2011) Sathyabhama, A.; Ashok Babu, T.P.Visualization of bubble nucleation during nucleate pool boiling outside a vertical cylindrical heated surface was done for ammonia-water binary mixture in order to obtain a descriptive behavior of the boiling, which was directly compared with the measured heat transfer coefficient data at low pressure of 4-8 bar and at low mass fraction of 0 < x < 0.3 and at different heat flux. Still images taken with high speed camera are used to demonstrate the decrease in boiling heat transfer coefficient with increase in ammonia mass fraction. Jensen and Memmel model has better agreement with experimental bubble diameter. Further work is required to obtain quantitative information about bubble nucleation parameters. It is found that both Calus and Rice and Stephan-Koorner correlation can predict the experimental heat transfer coefficient values with a maximum deviation of ±20%. © 2011 American Society of Mechanical Engineers.Item Thermodynamic analysis of window air conditioner using sustainable refrigerant R290/RE170 and R1270/RE170 blends as substitutes to refrigerant R22(International Information and Engineering Technology Association info@iieta.org, 2019) Vali, S.V.; Setty, A.B.T.P.The present work emphasis on theoretical computation of thermodynamic performance of window air conditioner using various sustainable R290/RE170 and R1270/RE170 refrigerant mixtures as substitutes to R22. In this work, apart from R407C, twelve new binary mixtures comprising of R290, R1270 and RE170 at various compositions were developed. And also in this investigation, a MATLAB code was developed to compute the thermodynamic performance characteristics of various considered R22 alternatives at Tk=54.4 0C and Te=7.2 °C. The various performance characteristics computed are mass flow rate, refrigeration effect, compressor work, coefficient of performance (COP), pressure ratio, compressor discharge temperature, power consumed per ton of refrigeration, condenser heat rejection and volumetric cooling capacity. Results showed that the COP of refrigerant mixture RM7 (R1270/RE170 95/5 by mass %) was the highest among twelve refrigerants studied and it was 0.23 % higher than R22. Pressure ratio of RM7 (3.174) was 7.49 % lower than that of R22 (3.431). Compressor discharge temperature of all the twelve investigated refrigerants was lower in the range of 9.35 0C to 17.15 0C when compared with R22. Power consumed per ton of refrigeration of RM7 was 0.27 % lower than that of R22. Volumetric cooling capacity of RM7 (3833 kJ/m3) was very close to that of R22 volumetric capacity (3863 kJ/m3). Heat transfer through condenser of RM7 (6.372 kW) was similar to that of R22 (6.377 kW). Overall, thermodynamic performance of RM7 matches well with the performance of base line refrigerant R22 and hence, refrigerant RM7 can be considered as sustainable alternative to R22 used in air conditioners. © 2019 International Information and Engineering Technology Association. All rights reserved.Item Exploring the synergistic interactions of TiO2, rGO, and g-C3N4 catalyst admixtures in a polystyrene nanocomposite photocatalytic film for wastewater treatment: Unary, binary and ternary systems(Elsevier Ltd, 2019) Das, S.; Mahalingam, H.Reduced graphene oxide (rGO) as well as graphitic carbon nitride (g-C3N4) were synthesised and blended along with TiO2 at specific ratios in polystyrene photocatalytic films to find out the optimum efficiency. The prepared photocatalysts were characterised by scanning electron microscopy (SEM-EDX), X-ray diffraction (XRD), Fourier transform infrared spectra (FTIR) and contact angle analyser. The SEM, XRD, and FTIR analysis indicated that the nanoparticles were evenly distributed on the surface of the polystyrene film. The stability of the polymer film with respect to possible leaching of the embedded catalyst particles was evaluated by ICP-OES analysis. The photocatalytic activity of the admixture was evaluated using remazol turquoise blue dye as a model organic pollutant, and it was found that the photocatalytic ternary admixtures displayed much higher photocatalytic activity (99%) than the unary (89%) or binary (94%) mixtures indicating the synergistic effect of these catalysts. The effect of catalyst ratio, immobilisation, pH, initial dye concentration, irradiated light source, the presence of H2O2 and reusability of the film were also evaluated. The degradation of the dye is confirmed by TOC analysis (40% reduction), and HPLC/MS was used to identify the final degraded compounds. © 2019 Elsevier Ltd.Item Compositional and Bath Temperature Effects on Heat Transfer During Quenching in Molten NaNO3–KNO3 Salt Mixtures(Springer, 2020) Pranesh Rao, K.M.P.; Prabhu, K.N.The present study involved the assessment of cooling severity of molten NaNO3–KNO3 mixtures which are widely used as quench media for austempering and martempering operations. An Inconel probe instrumented with thermocouples was quenched in molten NaNO3–KNO3 binary mixtures of varying concentration maintained at different quench bath temperatures. The temperature data acquired at various locations in the Inconel probe during quenching was used to calculate the spatially dependent transient heat flux at the metal–quenchant interface. Two critical points corresponding to peak heat extraction rates during the nucleate boiling stage and transition from boiling to convection stage were identified for each quench medium. The variation of average heat flux and average surface temperature corresponding to these critical points was mapped with variation in bath temperature and composition of the quench medium. AISI 4140 steel probes were quenched in these quench media maintained at 300 and 350 °C. The average hardness values measured in steel probes agreed with the cooling performance of these quench media determined using Inconel probe. The degree of uniformity in heat transfer as indicated by the spatial variation of normalized heat energy decreased with the increase in the concentration of KNO3 in the quench medium. A mechanism of boiling heat transfer during quenching based on thermochemical decomposition of the salt was proposed. © 2020, ASM International.Item Aspen Plus simulation of NH3-H2O-NaOH and NH3-H2O-KOH ternary cycles(Elsevier Ltd, 2022) Kolapkar, G.; Sathyabhama, A.The NH3-H2O is the most frequently utilized refrigerant-absorbent binary mixture in the vapor absorption refrigeration system (VARS) for low-temperature applications, but this mixture has the disadvantage of rectification requirement. To overcome this disadvantage, the researchers suggested the addition of salt to the binary NH3-H2O mixture. In this paper, a simulation of the ternary NH3-H2O-salt mixtures implemented in the VARS is presented. The NaOH and KOH salts are selected in the mass fraction range of 0 to 30% with 50 and 55% NH3 massconcentrations. The Aspen Plus process tool has been used to perform the simulation study. The addition of NaOH and KOH salts to the binary NH3-H2O mixture leads to an increase in thecoefficient of performance (COP) of the VARS with a simultaneous reduction in the initial generator operating temperature. The decrease in the generator temperature is slightly higher after adding NaOH salt than that by adding the KOH salt. TheCOP of thecycle increases after adding salt up to 20% salt mass fraction and then starts decreasing. The rise in the evaporator temperature leads to a gradual rise in theCOP of the ternary NH3-H2O-saltcycles. TheCOP of the ternary NH3-H2O-NaOHcycle is greater than that of the ternary NH3-H2O-KOHcycle under the same operating conditions. © 2022Item Effect of salt on the performance of ammonia absorption refrigeration cycle: A simulation study(Elsevier Ltd, 2024) Kolapkar, G.; Sathyabhama, A.To overcome the drawbacks associated with conventional binary mixtures (NH3-H2O and H2O-LiBr) in the vapor absorption refrigeration system (VARS), salt is added to the NH3-H2O mixture. The present simulation study analyzes the influence of adding LiBr and LiNO3 salts within a salt mass fraction range of 0 to 35% on the coefficient of performance (COP) of the NH3-H2O cycle. The simulations are conducted using Aspen Plus software. Furthermore, the influence of generator temperature on the COP and evaporator capacity of the ternary NH3-H2O-LiBr and NH3-H2O-LiNO3 cycles are also studied. The simulation results demonstrate that adding LiBr and LiNO3 salts improves the COP and reduces the initial temperature requirement in the generator of the VARS. Specifically, the NH3-H2O-LiBr cycle achieves the highest COP of 0.645 at an NH3 mass fraction of 55% and a LiBr mass fraction of 25%. This represents an 8.81% improvement compared to the COP of the NH3-H2O cycle. Similarly, the NH3-H2O-LiNO3 cycle exhibits the peak COP of 0.603 with the same NH3 mass fraction and LiNO3 mass fraction of 20%, which is 2.2% greater than the COP of the NH3-H2O cycle. Under similar operating conditions, the COP of the NH3-H2O-LiBr cycle is greater than that of the NH3-H2O-LiNO3 cycle. © 2024 Elsevier LtdItem Molecular simulation of fluid adsorption in nanoporous adsorbents: simple descriptors for space decontamination applications(Springer, 2025) Manokaran, R.; Aumond, T.; Eck, J.; Ergincan, O.; Daniel, C.; Farrusseng, D.; Coasne, B.We report a molecular simulation study on the adsorption-based trapping of different gaseous contaminants using nanoporous materials. In more detail, in the context of gas decontamination for space applications, we focus on adsorption from low pressures up to larger pressures of specific molecules ranging from water, hydrocarbons, and siloxanes. As far as the nanoporous adsorbents are concerned, we restrict the present study to a set of prototypical materials: an active carbon, a zeolite and a metal-organic framework. In addition to discussing the ability of each material type to adsorb specific gas molecules, we illustrate how simple descriptors such as Henry’s constant in the low-pressure range and the pressure at which half the nanoporosity gets filled can be used to rationalize and design molecular “getters” for space decontamination. Finally, by considering a specific yet representative binary gas mixture, we show that the adsorption of hydrophilic molecules– water– and hydrophobic molecules– siloxane– occurs without competitive/collective adsorption effect (provided adsorption occurs at low to moderate pressures). © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2025.