排序方式: 共有21条查询结果,搜索用时 15 毫秒
1.
S. Zeinali Heris F. Ahmadi Omid Mahian 《Journal of Dispersion Science and Technology》2013,34(10):1368-1375
An experimental study is performed to determine the pressure drop and performance characteristics of Al2O3/water and CuO/water nanofluids in a triangular duct under constant heat flux where the flow is laminar. The effects of adding nanoparticles to the base fluid on the pressure drop and friction factor are investigated at different Reynolds numbers. The results show that at a specified Reynolds number, using the nanofluids can lead to an increase in the pressure drop by 35%. It is also found that with increases in the Reynolds number, the rate of increase in the friction factor with the volume fraction of nanoparticles is reduced. Finally, the performance characteristics of the two nanofluids are investigated using the data of pressure drop and convective heat transfer coefficient. The results show that the use of Al2O3/water nanofluid with volume fractions of 1.5% and 2% is not helpful in the triangular duct. It is also concluded that at the same volume fraction of nanoparticles, using Al2O3 nanoparticles is more beneficial than CuO nanoparticles based on the performance index. 相似文献
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Amir Beheshti Mehdi Shanbedi Saeed Zeinali Heris 《Journal of Thermal Analysis and Calorimetry》2014,118(3):1451-1460
Power transformers play a key role in power and electrical industries and thus boosting their efficiency is necessary. In this study, the effect of oxidized multi-walled carbon nanotubes on transformer oil thermophysical properties was experimentally investigated. The maximum amount of carbon nanotubes was chosen up to 0.01 mass% to assure the maximum purity of transformer oil. Heat transfer characteristics of transformer oil and nanofluids in two cases of free and forced convection were studied. Breakdown voltage, flash point, pour point, density, electrical and thermal conductivities, viscosity and shear stress, as eight important quality parameters, were determined. According to the experimental results, the Breakdown voltage decreased through concentration increasing. Electrical conductivity is not changed considerable with increasing concentration and temperature. Thermal conductivity of nanofluids and transformer oil changed with increasing temperature and concentration. Furthermore, at all concentrations and temperatures, the viscosity of the nanofluids was lower than that of transformer oil. 相似文献
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Nanocomposite hydrogels are one of the most important types of biomaterials which can be used in many different applications such as drug delivery and tissue engineering.Incorporation of nanoparticles within a hydrogel matrix can provide unique characteristics like remote stimulate and improved mechanical strength.In this study,the synthesis of graphene oxide and graphene oxide nanocomposite hydrogel has been studied.Nanocomposite hydrogel was synthesized using carboxymethyl cellulose as a natural base,acrylic acid as a comonomer,graphene oxide as a filler,ammonium persulfate as an initiator,and iron nanoparticles as a crosslinking agent.The effect of reaction variables such as the iron nanoparticles,graphene oxide,ammonium persulfate,and acrylic acid were examined to achieve a hydrogel with maximum absorbency.Doxorubicin,an anti-cancer chemotherapy drug,was loaded into this hydrogel and its release behaviors were examined in the phosphate buffer solutions with different pH values.The structure of the graphene oxide and the optimized hydrogel were confirmed by Fourier-transform infrared spectroscopy,Raman spectroscopy,X-ray diffraction,scanning electron microscopy,and atomic force microscopy. 相似文献
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Mahdi?Saedshoar?Heris Mohammad?JavidiEmail author 《Mediterranean Journal of Mathematics》2017,14(3):134
In this paper, we study the fractional backward differential formula (FBDF) for the numerical solution of fractional delay differential equations (FDDEs) of the following form: \(\lambda _n {}_0^C D_t^{\alpha _n } y(t - \tau ) + \lambda _{n - 1} {}_0^C D_t^{\alpha _{n - 1} } y(t - \tau ) + \cdots + \lambda _1 {}_0^C D_t^{\alpha _1 } y(t - \tau ) + \lambda _{n + 1} y(t) = f(t), t \in [0,T]\), where \( \lambda _i \in \) \(\mathbb {R}\,(i = 1,\ldots ,n + 1)\,,\,\lambda _{n + 1} \ne 0,\,\, 0 \leqslant \alpha _1< \alpha _2< \cdots< \alpha _n < 1,\,\,T > 0,\) in Caputo sense. We find the Green’s functions for this equation corresponding to periodic/anti-periodic conditions in term of the Mittag-Leffler type. Our investigation is focused on stability properties of the numerical methods and we determine stability regions for the FDDEs. Finally, some numerical examples are given to show the effectiveness of the numerical method and the results are in excellent agreement with the theoretical analysis 相似文献
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Pourpasha Hadi Zeinali Heris Saeed Asadi Alireza 《Journal of Thermal Analysis and Calorimetry》2019,138(1):57-67
Journal of Thermal Analysis and Calorimetry - Today, nanoparticles are used as additives because of their unique properties. The aim of the present research is to investigate the effect of the... 相似文献
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Mehdi Dehghan Jalil Manafian Heris Abbas Saadatmandi 《Mathematical Methods in the Applied Sciences》2010,33(11):1384-1398
In this work, the homotopy perturbation method (HPM), the variational iteration method (VIM) and the Adomian decomposition method (ADM) are applied to solve the Fitzhugh–Nagumo equation. Numerical solutions obtained by these methods when compared with the exact solutions reveal that the obtained solutions produce high accurate results. The results show that the HPM, the VIM and the ADM are of high accuracy and are efficient for solving the Fitzhugh–Nagumo equation. Also the results demonstrate that the introduced methods are powerful tools for solving the nonlinear partial differential equations. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Coiled tubes and nanofludics are two significant techniques to enhance the heat transfer ability of thermal equipments. The forced convective heat transfer and the pressure drop of nanofluid inside straight tube and helical coiled one with a constant wall heat flux were studied experimentally. Distilled water was used as a host fluid and Nanofluids of aqueous TiO2 nanoparticles (50 nm) suspensions were prepared in various volume concentrations of 0.25–2 %. The heat transfer coefficient of nanofluids is obtained for different nanoparticle concentrations as well as various Reynolds numbers. The experiments covered a range of Reynolds number of 500–4,500. The results show the considerable enhancement of heat transfer rate, which is due to the nanoparticles present in the fluid. Heat transfer coefficient increases by increasing the volume concentration of nanoparticles as well as Reynolds number. Moreover, due to the curvature of the tube when fluid flows inside helical coiled tube instead of straight one, both convective heat transfer coefficient and the pressure drop of fluid grow considerably. Also, the thermal performance factors for tested nanofluids are greater than unity and the maximum thermal performance factor of 3.72 is found with the use of 2.0 % volume concentration of nanofluid at Reynolds number of 1,750. 相似文献
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Abstract Fluids in which nanometer-sized solid particles are suspended are called nanofluids. These fluids can be employed to increase the heat transfer rate in various applications. In this study, the convective heat transfer for Cu/water nanofluid through a circular tube was experimentally investigated. The flow was laminar, and constant wall temperature was used as thermal boundary condition. The Nusselt number of nanofluids for different nanoparticle concentrations, as well as various Peclet numbers, was obtained. Also, the rheological properties of the nanofluid for different volume fractions of nanoparticles were measured and compared with theoretical models. The results show that the heat transfer coefficient is enhanced by increasing the nanoparticle concentrations as well as the Peclet number. 相似文献