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141.
Natural convection heat transfer in Al2O3/water nanofluid is analyzed using the single-component nonhomogeneous lattice Boltzmann method (SCNHLBM). There exists a contradictory observation between the numerical and experimental works in the literature with respect to the heat transfer of nanofluids in natural convection. Nanofluid is treated as a single component with nonhomogeneous particle distribution introduced by a concentration transport equation of nanoparticles by considering the Brownian and thermophoretic diffusions. The average Nusselt number is found to deteriorate with increasing nanoparticle volume fraction; thus the trend of the experimental results is captured using SCNHLBM. Addition of Brownian and thermophoretic diffusion results in additional thermal diffusion and hence reduces the convective transport of heat. The contribution of Brownian and thermophoretic diffusions in heat transfer deterioration is revealed. 相似文献
142.
Heusler alloy Co2FeAl (CFA) nanoparticles have been synthesized by reducing a mixture of the precursors: CoCl2·6H2O, Fe(NO3)3·9H2O and AlCl3·6H2O under H2 atmosphere. XRD, SEM and TEM techniques have been used for the characterization of the prepared material. XRD and SAED data from TEM show the formation of mixed phases of L21, B2 and A2 type crystal structure of the alloy. The estimated particle size from XRD data and TEM micrograph has been found in the range of 10 nm to 50 nm. The saturation magnetization has been found of 115 emu/g from M-H characteristics which is close to its bulk value of saturation magnetization. Chemical composition of the elements has also been estimated from EDAX, which shows a ratio of Co:Fe:Al as 2.12:1.06:0.81. 相似文献
143.
L.N.S.A. Thummalakunta Chian Haw YongKrishnamoorthy Ananthanarayanan Joachim Luther 《Organic Electronics》2012,13(10):2008-2016
We present a solution-processed pseudo bi-layer organic solar cell with poly(3-hexyl thiophene) (P3HT) as donor and indene-C60 bisadduct (ICBA) as acceptor. The devices were fabricated by sequential processing of the active components followed by a thermal annealing treatment. An efficiency of 5.9% was achieved under AM 1.5G irradiation (1000 W/m2). The obtained efficiency is attributed to an enhanced nanomorphology that arises from the inter-diffusion of the ICBA molecules into a layer of pre-organised polymer (P3HT) and also due to the subsequent crystallisation of the ICBA molecules. These processes facilitate efficient charge generation and extraction. Time of flight-secondary ion mass spectroscopy (TOF-SIMS) depth profiling was carried out for different thermal annealing treatments of these pseudo bi-layer devices, which reveals full inter-diffusion of ICBA into the polymer P3HT. Photo-CELIV (charge extraction by linearly increasing voltage) studies elucidates that the thermal annealing imparts crystallinity to the fullerene phase which results in the improvement of charge carrier mobility. 相似文献
144.
Arvind S. More Sharad K. Pasale Pandurang N. Honkhambe Prakash P. Wadgaonkar 《应用聚合物科学杂志》2011,121(6):3689-3695
Poly(ether ether ketone)s and poly(ether ether ketone ketone)s containing pendant pentadecyl chains were synthesized by polycondensation of each of the two bisphenol monomers viz, 1,1,1‐[bis(4‐hydroxyphenyl)‐4′‐pentadecylphenyl]ethane and 1,1‐bis(4‐hydroxyphenyl)‐3‐pentadecyl cyclohexane with activated aromatic dihalides namely, 4,4′‐difluorobenzophenone, and 1,3‐bis(4‐fluorobenzoyl)benzene in a solvent mixture of N,N‐dimethylacetamide and toluene, in the presence of anhydrous potassium carbonate. Polymers were isolated as white fibrous materials with inherent viscosities and number average molecular weights in the range 0.70–1.27 dL g?1 and 76,620–1,36,720, respectively. Poly(ether ether ketone)s and poly(ether ether ketone ketone)s were found to be soluble at room temperature in organic solvents such as chloroform, dichloromethane, tetrahydrofuran, and pyridine and could be cast into tough, transparent, and flexible films from their solutions in chloroform. Wide angle X‐ray diffraction patterns exhibited a broad halo at around 2θ = ~ 19° indicating that the polymers containing pentadecyl chains were amorphous in nature. In the small‐angle region, diffuse reflections of a typically layered structures resulting from the packing of pentadecyl side chains were observed. The temperature at 10% weight loss, obtained from TG curves, for poly(ether ether ketone)s and poly(ether ether ketone ketone)s were in the range 416–459°C, indicating their good thermal stability. A substantial drop in glass transition temperatures (68–78°C) was observed for poly(ether ether ketone)s and poly(ether ether ketone ketone)s due to “internal plasticization” effect of flexible pendant pentadecyl chains. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011 相似文献
145.
146.
Hyun Tae Hwang Patrick Greenan Seung Jin Kim Arvind Varma 《American Institute of Chemical Engineers》2013,59(9):3359-3364
We have recently demonstrated that boric acid (H3BO3, BA) is a promising additive to decrease onset temperature as well as to enhance hydrogen release kinetics for thermolysis of ammonia borane (NH3BH3, AB). The observations suggest that tetrahydroxyborate ion released by heating BA serves as Lewis acid and catalyzes AB dehydrogenation. Using this approach, we obtained high H2 yield at 85°C, along with rapid kinetics. Various operating conditions were investigated, such as reactor temperature, AB wt %, and particle size of BA. Even in the presence of 10 wt % BA, high H2 yield (13 wt %) and trace amount of ammonia (10–20 ppm) were obtained at 80°C, proton exchange membrane (PEM) fuel cell operating temperature. To our knowledge, such H2 yield value is higher than from any other method using AB with additive or catalyst at PEM fuel cell operating temperatures. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3359–3364, 2013 相似文献
147.
Reza Haghpanah Ricky Nilam Arvind Rajendran Shamsuzzaman Farooq Iftekhar A. Karimi 《American Institute of Chemical Engineers》2013,59(12):4735-4748
A systematic analysis of several vacuum swing adsorption (VSA) cycles with Zeochem zeolite 13X as the adsorbent to capture CO2 from dry, flue gas containing 15% CO2 in N2 is reported. Full optimization of the analyzed VSA cycles using genetic algorithm has been performed to obtain purity‐recovery and energy‐productivity Pareto fronts. These cycles are assessed for their ability to produce high‐purity CO2 at high recovery. Configurations satisfying 90% purity‐recovery constraints are ranked according to their energy‐productivity Pareto fronts. It is shown that a 4‐step VSA cycle with light product pressurization gives the minimum energy penalty of 131 kWh/tonne CO2 captured at a productivity of 0.57 mol CO2/m3 adsorbent/s. The minimum energy consumption required to achieve 95 and 97% purities, both at 90% recoveries, are 154 and 186 kWh/tonne CO2 captured, respectively. For the proposed cycle, it is shown that significant increase in productivity can be achieved with a marginal increase in energy consumption. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4735–4748, 2013 相似文献
148.
Arvind Pattamatta 《International Journal of Thermal Sciences》2010,49(9):1485-1492
Carbon nanotube (CNT) contacts play a promising role in thermal management devices due to their high thermal conductivity. However, at the CNT–substrate contacts, interfacial thermal resistance (ITR) may significantly reduce the heat transfer ability of carbon nanotube interconnects. An in depth understanding of the thermal transport in CNT–substrate contacts is therefore essential, considering the fact that very few experimental results for these contacts are available. In this computational study, the heat transport in 3-D hollow CNT/SiO2 and CNT/Si contacts at room temperature are modeled using the Boltzmann transport equation for phonons. An isotropic assumption for the dispersion relations of graphite has been used to calculate the material properties of CNT. The present simulation for the CNT/SiO2 contact predict the ITR to be of the same order as that of the theory. However, the computed ITR is two orders of magnitude smaller than that of the experimental value. The discrepancy between the measured and predicted values of thermal contact resistances may be attributed to the imperfect contact and the presence of catalyst particles in between the CNT and SiO2 substrate in the experiment, the assumption of isotropic phonon dispersion and the use of Debye model to calculate the material properties. For the CNT/Si contact, the value of ITR obtained using the phonon sine function dispersion model is an order of magnitude higher than that of the Debye Model. It is determined that the length of the CNT and substrate do not have a significant effect on the thermal contact resistance. The thermal contact resistances are found to decrease with increasing values of the CNT diameter and thickness and are relatively independent of substrate diameter. 相似文献
149.
Rakesh Kumar A. Arvind M. Goswami S. Bhattacharya V. K. Shrikhande G. P. Kothiyal 《Journal of Materials Science》2009,44(13):3349-3355
We have prepared lithium zinc silicate (LZS) glasses of compositions (mol%) 17.83Li2O–17.73ZnO–(53.52 − x)SiO2–5.25Na2O–1.25P2O5–4.31B2O3–x-NiO, where 0.5 ≤ x ≤ 2.0, by the melt quench technique. The effect of NiO on the phase formation, thermo-physical properties and sealing behaviour
of LZS glass–ceramics was studied using X-Ray diffraction (XRD), thermo-mechanical analysis (TMA) and microhardness (MH) measurements.
It is found that NiO incorporation leads to a change in the role of ZnO from network modifier to intermediate oxide. The intermediate
network forming Zn2+ ions would find it more difficult to diffuse and initiate the transformation of Li3Zn0.5SiO4 to Li2ZnSiO4. Thus Li3Zn0.5SiO4 is formed instead of Li2ZnSiO4 on addition of 2 mol% NiO. Scanning electron microscopy (SEM) and energy dispersive analysis of X-rays (EDAX) measurements
at the glass–ceramic-to-metal interface reveal a change in the microstructure commensurate with the changing role of ZnO.
Addition of NiO favoured interdiffusion of species at the interface leading to better sealing. 相似文献
150.
In this communication, an analytical expression for the water temperature of an integrated photovoltaic thermal solar (IPVTS) water heater under constant flow rate hot water withdrawal has been obtained. Analysis is based on basic energy balance for hybrid flat plate collector and storage tank, respectively, in the terms of design and climatic parameters. Further, an analysis has also been extended for hot water withdrawal at constant collection temperature. Numerical computations have been carried out for the design and climatic parameters of the system used by Huang et al. [Huang BJ, Lin TH, Hung WC, Sun FS. Performance evaluation of solar photovoltaic/thermal systems. Sol Energy 2001; 70(5): 443–8]. It is observed that the daily overall thermal efficiency of IPVTS system increases with increase constant flow rate and decrease with increase of constant collection temperature. The exergy analysis of IPVTS system has also been carried out. It is further to be noted that the overall exergy and thermal efficiency of an integrated photovoltaic thermal solar system (IPVTS) is maximum at the hot water withdrawal flow rate of 0.006 kg/s. The hourly net electrical power available from the system has also been evaluated. 相似文献