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In this work, heat transfer and pressure drop characteristics of graphene oxide/water nanofluid flow through a circular tube having a wire coil insert were studied. The required graphene oxide was synthesized via the Hummer method and characterized using Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (SRD), and scanning electron microscope (SEM) methods. Dispersing graphene oxide in the water, nanofluids with 0.02, 0.07, and 0.12% volume fraction were prepared. An experimental set-up was designed and made to investigate the heat transfer performance and pressure loss of nanofluids. All experiments were carried out in the constant heat flux at tube wall conditions. The volumetric flow rates of the nanofluid were adjusted at 6, 8, and 10 L/min. Thermal conductivity, specific heat, density, and viscosity as thermophysical properties of the nanofluid were calculated using graphene oxide and water properties at the average temperature via appropriate relations. These properties were applied to calculate the convective heat transfer coefficient, Nusselt number, and friction factors for each experiment. Finally, the constant and exponents of Duangthongsuk and Wongwises's correlations for Nusselt number and friction factor were corrected by experimental results. The achieved experimental data have shown good agreement with those predicted. The results have shown that 0.12 vol% of graphene oxide in the water can enhance convective heat transfer coefficient by about 77%. As a result, it can be concluded that the graphene oxide/water can be used in the heat transfer devices to achieve more efficiency. 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
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Abstract This article presents an experimental investigation where the thermal conductivity and viscosity of silver-deionized water nanofluid is measured and studied. The mixture consists of silver nanoparticles of 0.3, 0.6, and 0.9% of volume concentrations and studied for temperatures between 50°C and 90°C. The transient hot-wire apparatus and Cannon-Fenske viscometer are used to measure the thermal conductivity and kinematic viscosity of nanofluid, respectively. The thermal conductivity increases with the increase in temperature and particle concentrations. A minimum and maximum enhancement of 27% at 0.3 vol% and 80% at 0.9 vol% are observed at an average temperature of 70°C. The viscosity decreases with the increase in temperature and increases with the increase in particle concentrations. The effect of Brownian motion and thermophoresis on the thermo-physical properties is discussed. Thus, an experimental correlation for thermal conductivity and viscosity, which relates the volume concentration and temperature, is developed, and the proposed correlation is found to be in good agreement with the experimental results. 相似文献
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This article examines the magnetohydrodynamic (MHD) flow of non-Newtonian nanofluid in a pipe. The temperature of the pipe is assumed to be higher than the temperature of the fluid. In particular two temperature dependent viscosity models, have been considered. The nonlinear partial differential equations along with the boundary conditions are first cast into a dimensionless form and then the equations are solved by homotopy analysis method (HAM). Explicit analytical expressions for the velocity field, the temperature distribution and nano concentration have been derived analytically. The effects of various physical parameters on velocity, temperature and nano concentration are discussed by using graphical approach. 相似文献
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用一种强有力的解析方法,称为Adomian分解法(ADM),来研究磁场和纳米颗粒对Jeffery-Hamel流动的影响.将该问题模型的控制方程,即将传统的流体力学Navier-Stokes方程和Maxwell电磁方程,简化为非线性的常微分方程.该方法得到的结果与Runge-Kutta方法得到的数值结果相一致,结果用表格列出.不同α,Ha和Re数下的图形表明,本方法可以得到高精度的结果.首先对不同的Hartmann数和管壁倾角,研究喇叭形管道中的流场;最后在没有磁场作用时,研究纳米固体颗粒体积率的影响. 相似文献
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M. SALARI M. MOHAMMADTABAR A. MOHAMMADTABAR 《应用数学和力学(英文版)》2014,35(1):63-72
The numerical analysis of heat transfer of laminar nanofluid flow over a fiat stretching sheet is presented. Two sets of boundary conditions (BCs) axe analyzed, i.e., a constant (Case 1) and a linear streamwise variation of nanopaxticle volume fraction and wall temperature (Case 2). The governing equations and BCs axe reduced to a set of nonlinear ordinary differential equations (ODEs) and the corresponding BCs, respectively. The dependencies of solutions on Prandtl number Pr, Lewis number Le, Brownian motion number Nb, and thermophoresis number Nt are studied in detail. The results show that the reduced Nusselt number and the reduced Sherwood number increase for the BCs of Case 2 compared with Case 1. The increases of Nb, Nt, and Le numbers cause a decrease of the reduced Nusselt number, while the reduced Sherwood number increases with the increase of Nb and Le numbers. For low Prandtl numbers, an increase of Nt number can cause to decrease in the reduced Sherwood number, while it increases for high Prandtl numbers. 相似文献
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The boundary layer flow of a nanofluid past a stretching/shrinking sheet with hydrodynamic and thermal slip boundary conditions is studied. Numerical solutions to the governing equations are obtained using a shooting method. The results are found for the skin friction coefficient, the local Nusselt number, and the local Sherwood number as well as the velocity, temperature, and concentration profiles for some values of the velocity slip parameter, thermal slip parameter, stretching/shrinking parameter, thermophoresis parameter, and Brownian motion parameter. The results show that the local Nusselt number, which represents the heat transfer rate, is lower for higher values of thermal slip parameter, thermophoresis parameter, and Brownian motion parameter. 相似文献
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Analytical expressions for nucleate pool boiling heat transfer of nanofluid in the critical heat flux (CHF) region are derived taking into account the effect of nanoparticles moving in liquid based on the fractal geometry theory. The proposed fractal model for the CHF of nanofluid is explicitly related to the average diameter of the nanoparticles, the volumetric nanoparticle concentration, the thermal conductivity of nanoparticles, the fractal dimension of nanoparticles, the fractal dimension of active cavities on the heated surfaces, the temperature, and the properties of the fluid. It is found that the CHF of nanofluid decreases with the increase of the average diameter of nanoparticles. Each parameter of the proposed formulas on CHF has a clear physical meaning. The model predictions are compared with the existing experimental data, and a good agreement between the model predictions and experimental data is found. The validity of the present model is thus verified. The proposed fractal model can reveal the mechanism of heat transfer in nanofluid. 相似文献