Department of Mechanical engineering
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Item Thermal conductivity enhancement of magnetic nanofluids for energy applications(Elsevier, 2023) Parameshwaran, R.Nanofluids are a class of fascinating energy transfer fluids that are gaining impetus in many heat transfer applications due to their tremendous potential in augmenting the thermal properties of the base fluids such as water, ethylene glycol, engine oil and so on. From this perspective, this study was aimed at investigating the enhancement of thermal conductivity of distilled water (base fluid) using magnetic nanoparticles. The magnetic nanoparticles were experimented for understanding their surface morphology, crystal structure, chemical stability, thermal conductivity and viscosity using the respective characterization techniques. The scanning electron microscopy results infer that the average size of the agglomerated spherically shaped magnetic nanoparticles was 600.8 nm, however the size of individual particles was observed to be well within 100 nm. The X-ray diffraction pattern showed prominent intense peaks at 29.87°, 35.61° and 63° which have justified the crystalline nature of the nanoparticles. The as-prepared magnetic nanofluids (MNF) when tested for its surface structure has revealed good chemical stability between the base fluid and the magnetic nanoparticles. It is noteworthy that, the thermal conductivity of the MNF was ranging from 0.7666 W/m K to 0.9666 W/m K for the volume fraction of nanoparticles ranging from 0.01 % to 0.1 % and temperature ranging from 35° C to 55 °C. The significance of this work has been justified in terms of achieving enhanced thermal conductivity ranging from 21.3 % to 53.1 % for such low volume fractions of the nanoparticles. Furthermore, the MNF exhibited only marginal variations in viscosity for the specified volume fractions of the nanoparticles. In summary, the as-prepared MNF with these enhanced attributes can be considered to be viable and beneficial for the energy applications.Item Analytical and experimental investigations of nanoparticles embedded phase change materials for cooling application in modern buildings(Elsevier, 2012-03) Parameshwaran, R.his paper presents the analytical and experimental investigations of the phase change heat transfer characteristics and thermodynamic behavior of spherically enclosed phase change material (PCM) with dispersion of nanoparticles for latent thermal energy storage (LTES) system in buildings. In this study, the heat transfer characteristics in terms of the transient temperature variations, moving interface positions, complete rate of solidification and melting were analyzed for the six different PCMs considered in pure form and with dispersed nanoparticles as well. The heat transfer characteristics of the PCMs considered were analytically modeled and experimentally evaluated for the steady state and transient conditions for various heat generation parameters during freezing and melting cycles of the LTES system. The experimental results infer that for the same thermal load conditions the rate of solidification for the PCMs decreased with the increased mass fractions of nanoparticles while compared to the pure PCMs. For the same operating conditions of the LTES system, similar heat transfer characteristics were observed for the six PCMs considered. In this paper, the analytical model solutions and experimental results for the 60% n-tetradecane: 40% n-hexadecane PCM are presented. The solidification time for the 60% n-tetradecane: 40% n-hexadecane PCM embedded with the aluminium and alumina nanoparticles were expected to reduce by 12.97% and 4.97% than at its pure form respectively. Besides, the test results indicate that by increasing the mass fraction of the nanoparticles beyond the limiting value of 0.07 the rate of solidification was not significant further. Furthermore, the rate of melting was improved significantly for the PCMs embedded with the dispersed nanoparticles than the pure PCMs. The analytical solutions obtained for the pure and dispersed nanoparticles based PCMs were validated using the experimental results. The deviations observed between the analytical solutions and the experimental results were in the range of 10%–13%. Based on the analytical and experimental results the present nanoencapsulated LTES system can be regarded as a potential substitute for the conventional LTES system in buildings for achieving enhanced heat transfer characteristics and energy efficiency.Item Experimental investigation on convective heat transfer and rheological characteristics of Cu–TiO2 hybrid nanofluids(Elsevier, 2014-01) Parameshwaran, R.An experimental study has been carried out to investigate the heat transfer potential and rheological characteristics of copper–titania hybrid nanofluids (HyNF) using a tube in the tube type counter flow heat exchanger. The nanofluids were prepared by dispersing the surface functionalized and crystalline copper–titania hybrid nanocomposite (HyNC) in the base fluid, with volume concentrations ranging from 0.1% to 2.0%. The Heat transfer and rheological characteristics of nanofluids containing HyNC of an averaged size of 55 nm were experimentally investigated. The test results reveal that the convective heat transfer coefficient, Nusselt number and overall heat transfer coefficient were increased by 52%, 49% and 68% respectively, up to 1.0% volume concentration of HyNC. Beyond the volume concentration of 1.0% and up to 2.0%, the reduction in the convective heat transfer potential and the Nusselt number were marginal, which signified the effective thermal conductivity enhancement in HyNF. The functionalized structure and crystalline nature of HyNC acted as extended surfaces within the fluid medium, thereby creating more thermal interfaces for achieving improved thermal conductivity and the heat transfer potential of HyNF. The friction factor and pressure drop of HyNF for 2.0% volume concentration were expected to be 1.7% and 14.9% respectively, which implies a penalty in the pumping capacity. However, the enhancement in the heat transfer characteristics and acceptable variations in rheological aspects of HyNF, would help to reduce the consumption of higher volume concentration of metallic or metal oxide nanostructures, to be dispersed in the fluid medium. In order to validate the experimental measurements, a new correlation was developed, which predicted the experimental data with a maximum deviation of +7% and −4% for all the volume concentrations of HyNF. The present correlation was in good agreement with the experiments and can be helpful in predicting the heat transfer potential of HyNF.