Journal Articles
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Item A review on thermal energy storage using composite phase change materials(Bentham Science Publishers, 2018) Chavan, S.; Gumtapure, V.; Arumuga Perumal, D.A.Background: This paper intends to provide the elementary understanding about the development of thermal energy storage systems. Reviews of storage system performance are carried out from various characterization studies, experimental work, numerical investigations and patents. Several techniques employed to enhance the thermal performance have been reviewed and discussed. Composite phase change materials are the best alternative to achieve the cost feasibility in thermal energy storage systems without compromising the storage capacity. Objective: The purpose of this study is to give an outline and history of the thermal energy storage systems and enlighten the techniques used for storage density enhancement without significant modifications in the design. Methods: In this study, three methods such as, characterization studies, experimental work, numerical investigations and patents. It also addresses many research articles and recent patents on the thermal storage systems, various techniques adopted and applications of such systems. Results: Composite phase change materials are the best alternative to achieve the cost feasibility in thermal energy storage systems without compromising the storage capacity. Carbon based nanoparticles show excellent properties in the composite phase change materials. Conclusion: Composite phase change materials have greater potential for thermal energy storage applications and especially carbon-based nanoparticles like graphene, graphene oxide, carbon nanotubes, fullerene, graphite, graphite oxide, extracted graphite etc., are greatly enhancing the thermo-physical properties of composite phase change materials. Combination of paraffin-based phase change materials and carbon-based nanoparticles can be used for the future thermal energy storage applications. © 2018 Bentham Science Publishers.Item Potential of Chitosan and its derivatives for controlled drug release applications – A review(Editions de Sante editions.de.sante@wanadoo.fr, 2019) Safdar, R.; Omar, A.A.; Arunagiri, A.; Iyyaswami, R.; Murugesan, M.Recent research on the drug delivery systems exhibited tremendous improvements for several short life drugs which disappear in few minutes in harsh conditions of the Gastrointestinal tract (GIT). After years of investigations, the current drug delivery system has been improved with new advanced materials with less toxicity and better therapeutic efficiency. In this regard, new formulations consisting of drugs encapsulated with natural biodegradable copolymer, Chitosan, in the form of nanoparticles have been studied, which in turn improved the release profile of drugs. In this review, the Chitosan and its physiochemical properties, nanoparticles and their drug release mechanism and effects of modification of various drugs (anti–cancer, anti–inflammatory, anti–diabetes, anti–infectious drugs etc) with Chitosan and co–materials on their release profiles are briefly reviewed. These biodegradable polymeric nanoparticles improved the in vitro release profile of drugs and provided a way forward for further improvement of the current and conventional drug delivery systems. © 2018 Elsevier B.V.Item Critical heat flux enhancement in pool boiling using alumina nanofluids(2010) Hegde, R.N.; Rao, S.S.; Reddy, R.P.The pool boiling characteristics of dilute dispersions of alumina nanoparticles in water were studied. Consistent with other nanofluid studies, it was found that a significant enhancement in critical heat flux (CHF) can be achieved at modest nanoparticle concentrations (<0.1% by volume). During experimentation and subsequent inspection, formation of a porous layer of nanoparticles on the heater surface occurred during nucleate boiling. This layer significantly changes surface texture of the heater wire surface which could be the reason for improvement in the CHF value. © 2010 Wiley Periodicals, Inc.Item Role of surface roughness in pool boiling with Alumina-water nanofluid on a horizontal wire surface(International Information and Engineering Technology Association, 2011) Hegde, R.N.; Rao, S.S.; Reddy, R.P.Boiling heat transfer is one of the major phenomenon which of late, has drawn the attention of many researchers and scientists throughout the world. With nanofluids, further boost is given in heat transfer enhancement. This research paper is the study of heat transfer enhancement using Alumina nanofluid in different volume concentrations ranging from 1 to 9%. The role of surface roughness on critical heat flux enhancement (CHF) in pool boiling with nanofluids was experimentally studied using a 36 gauge NiCr wire at atmospheric pressure. Experimentation included i) investigations on boiling heat transfer subjecting the wire surface to Alumina nanofluid at higher volume concentrations and ii) investigations on surface roughness due to surface coating, subjecting the wire surface to a single heating cycle with different volume concentrations of Alumina nanofluid. Boiling of nanofluid resulted in nanoparticle deposition and subsequent roughning of the wire surface. To substantiate the nanoparticle deposition and its effect on critical heat flux, investigation was done by studying the surface roughness and SEM images of the wire surface. The experimental results show the evidence of nanoparticle deposition on the wire surface and its effect on CHF enhancement and deterioration in pool boiling heat transfer.Item Crystallinity, conductivity, and magnetic properties of PVDF-Fe 3O4 composite films(2011) Bhatt, A.S.; Bhat, D.K.; Santosh, M.S.The formation of Fe3O4 nanoparticles by hydrothermal process has been studied. X-ray Diffraction measurements were carried out to distinguish between the phases formed during the synthesis. Using the synthesized Fe3O4 nanoparticles, poly(vinyledene fluoride)-Fe3O4 composite films were prepared by spin coating method. Scanning electron microscopy of the composite films showed the presence of Fe3O4 nanoparticles in the form of aggregates on the surface and inside of the porous polymer matrix. Differential Scanning calorimetry revealed that the crystallinity of PVDF decreased with the addition of Fe3O4. The conductitivity of the composite films was strongly influenced by the Fe3O4 content; conductivity increased with increase in Fe3O4 content. Vibration sample magnetometry results revealed the ferromagnetic behavior of the synthesized iron oxide nanoparticles with a Ms value of 74.50 emu/g. Also the presence of Fe3O4 nanoparticles rendered the composite films magnetic. © 2010 Wiley Periodicals, Inc.Item Enhancement of heat transfer characteristics of transformer oil by addition of aluminium nanoparticles(2011) Rajesh, E.; Prabhu, K.N.A two step approach involving the synthesis of Al nanoparticles by mechanical milling followed by dispersion of the nanoparticles in the base fluid is adopted in the present work to prepare transformer oil based nanofluids. Stainless steel (AISI 304) probes of diameter 15 mm and height 70 mm were used to determine the cooling rate intensities of nanofluids. Heat transfer coefficients were determined using Kobasko's method. A dynamic contact angle analyzer was used to determine the contact angle of the droplet on the substrate. The addition of Al nanoparticles to the base fluid decreases the wettability and improves its heat transfer capability. The vapour phase stage existed for a longer period of time for transformer oil than for Al-transformer oil based nanofluids. The dispersion of nanoparticles in the base fluid is believed to disrupt the vapour blanket stage in the early stage of the cooling process. The peak heat transfer coefficient increases with an increase in the Al nanoparticle content in the oil. The addition of 0.5 vol % nanoparticles enhances the peak heat transfer coefficient by about 70 %. Copyright © 2011 by ASTM International.Item Microwave-assisted synthesis and magnetic studies of cobalt oxide nanoparticles(2011) Bhatt, A.S.; Bhat, D.K.; Tai, C.-W.; Santosh, M.S.An efficient microwave-assisted route has been used to synthesize nanoparticles of cobalt oxide. The particles were well characterized by transmission electron microscopy (TEM) which showed that the average diameter of the particles is around 6 nm. X-ray diffraction (XRD) studies further confirmed the formation of the spinel Co3O4. Purity of the products was detected by Fourier transform infrared spectroscopy (FTIR) combined with thermal gravimetric analysis (TG/DTG). The magnetic measurements revealed a small hysteresis loop at room temperature indicating a weak ferromagnetic nature of the synthesized Co3O4 nanoparticles. The magnetic moment of the particles was measured to be 4.27 ?eff. © 2010 Elsevier B.V. All rights reserved.Item Behavioral study of alumina nanoparticles in pool boiling heat transfer on a vertical surface(2011) Hegde, R.N.; Reddy, R.P.; Rao, S.S.Experiments were carried out to investigate the pool boiling of alumina-water nanofluid at 0.1 g/l to 0.5 g/l of distilled water, and the nucleate pool boiling heat transfer of pure water and nanofluid at different mass concentrations were compared at and above the atmospheric pressure. At atmospheric pressure, different concentrations of nanofluids display different degrees of deterioration in boiling heat transfer. The effect of pressure and concentration of nanoparticles revealed significant enhancement in heat flux and deterioration in pool boiling. The heat transfer coefficient of 0.5 g/l alumina-water nanofluid was compared with pure water and clearly indicates deterioration. At all pressures the heat transfer coefficients of the nanofluid were lower than those of pure water. Experimental observation revealed particles coating over the heater surface and subsequent SEM inspection of the heater surface showed nanoparticles coating on the surface forming a porous layer. To substantiate the nanoparticle deposition and its effect on heat flux, investigation was done by measuring the surface roughness of the heater surface before and after the experiment. While SEM images of the heater surface revealed nanoparticle deposition, surface roughness of the heater surface confirmed it. Based on the experimental investigations it can be concluded that an optimum thickness of nanoparticles coating favors an increase in heat flux. Higher surface temperature due to the presence of nanoparticles coating results in the deterioration of boiling heat transfer. © 2011 Wiley Periodicals, Inc.Item The fabrication, characterization and electrochemical corrosion behavior of Zn-TiO2 composite coatings(2011) Punith Kumar, M.K.; Venkatesha, T.V.; Pavithra, M.K.; Nithyananda Shetty, A.Metal-nanoparticle composite coatings improve the hardness, wear resistance and corrosion resistance properties of metal coatings. In this work, TiO 2 nanoparticles were chosen as second-phase particles to generate anticorrosive Zn composite coatings. The TiO2 nanoparticles were dispersed in a Zn plating solution to co-deposit them with Zn. The Zn-TiO 2 composite coatings were then characterized by scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS) and x-ray diffraction methods. The presence of TiO2 particles in the composite was confirmed by SEM images and EDS spectra. The Zn-TiO2 composite coatings incorporated with different amounts of TiO2 particles were tested for corrosion performance by polarization and electrochemical impedance spectroscopy, and the dissolution behavior of the coatings that had been immersed in corrosive media for a long time was studied. Improved corrosion resistance properties of the Zn-TiO2 composite coatings were confirmed by polarization studies, fitted Nyquist plots, an increase in phase angle and a shift in the Rct characteristic peak of the Bode plot. © 2011 The Royal Swedish Academy of Sciences.Item Chitosan/NiO nanocomposites: A potential new dielectric material(2011) Bhatt, A.S.; Bhat, D.K.; Santosh, M.S.; Tai, C.-W.The study of electrochemical behavior of organic-inorganic nanocomposite materials remains a major challenge for application in energy storage devices. Here, new composite materials of chitosan and NiO nanoparticles have been fabricated. The NiO nanoparticles are well characterized by infrared spectroscopy, X-ray diffraction and transmission electron microscopy. The electrical properties of the films are studied by impedance spectroscopy at different temperatures; and thereby permittivity, electric modulus and conductivity data are obtained. By studying the variations in permittivity and electric modulus spectra with respect to applied frequency signal and temperature, the ionic conductivity of the material is investigated. The Correlated Barrier Hopping model is employed to understand the conduction mechanism. An admirable conductivity of 1.4 × 10-2 S cm -1 is obtained for a nanocomposite with 4 wt% NiO content. The activation energies of the composite films decrease with increase in NiO content, from 16.5 to 4.8 kJ mol-1. © 2011 The Royal Society of Chemistry.