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1.
Yuhiro Iwamoto Hiroshi Yamaguchi Xiao-Dong Niu 《Journal of magnetism and magnetic materials》2011,323(10):1378-1383
The magnetic body force in boiling two-phase temperature-sensitive magnetic fluid (TSMF) flow is known to effectively increase the driving force of magnetic fluid in a non-uniform magnetic field. Based on this mechanism, in the present study, a binary TSMF, which is a mixture of the TSMF and a low-boiling-saturation-temperature organic solution, is proposed to be used in a heat transport device to enhance its circulation. In order to see its performance in the heat transport device, the pressure difference at different heated temperatures, magnetic fields and inclination angles of the heating section are investigated experimentally and theoretically. Results showed that the driving force increases remarkably due to more gas phase appearing in the test fluid and the magnetization of it decreasing. At low magnetic field the driving force is enhanced greatly when the inclination angle is close to 60°, while at high magnetic field the driving force is remarkably enhanced due to the effect of the magnetic force in the inclination angle range from 0° to 30° and 60° to 90°. 相似文献
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Hiroshi Yamaguchi Xiao-Dong Niu Xin-Rong Zhang Keisuke Yoshikawa 《Journal of magnetism and magnetic materials》2009,321(22):3665-3670
In this article, natural convections of a magnetic fluid in a cubic cavity under a uniform magnetic field are investigated experimentally and numerically. Results obtained from experiments and numerical simulations reveal that the magnetic field and magnetization are influenced by temperature. There exist relative larger magnetization and magnetic forces in the regions near the upper wall and center inside the cavity than in the region near the bottom and side walls. A weak flow roll occurs inside cavity under the magnetic force, and it brings the low temperature fluid downward in the center region, and streams the high temperature fluid upward along the regions near the sidewalls. With the magnetic field imposed, the heat transfer inside the cavity is enhanced significantly compared to that without the magnetic field, and increasing the strength of the magnetic field the heat transfer is increased further. 相似文献
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利用格 子 Boltzmann方法模拟矩形腔内纳米流体Rayleigh-Benard对流, 得到温度场和流线分布, 比较分析不同Ra数、体积分数、粒径下纳米流体对流换热的变化情况. 结果表明: 在相同的Ra 数和体积分数下, 纳米流体的对流换热随着粒径的增大而减弱; 在相同的Ra数和粒径下, 纳米流体的对流换热随着体积分数增大而增强.
关键词:
纳米流体
Raleigh-Benard
多相流
格子Boltzmann方法 相似文献
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Coupled flow and heat transfer of power-law nanofluids on non-isothermal rough rotary disk subjected to magnetic field
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Yun-Xian Pei 《中国物理 B》2022,31(6):64402-064402
We study the coupled flow and heat transfer of power-law nanofluids on a non-isothermal rough rotating disk subjected to a magnetic field. The problem is formulated in terms of specified curvilinear orthogonal coordinate system. An improved BVP4C algorithm is proposed, and numerical solutions are obtained. The influence of volume fraction, types and shapes of nanoparticles, magnetic field and power-law index on the flow, and heat transfer behavior are discussed. The obtained results show that the power-law exponents (PLE), nanoparticle volume fraction (NVF), and magnetic field inclination angle (MFIA) have almost no effects on velocities in the wave surface direction, but have small or significant effects on the azimuth direction. The NVF has remarkable influences on local Nusselt number (LNN) and friction coefficients (FC) in the radial direction and the azimuth direction (AD). The LNN increases with NVF increasing while FC in AD decreases. The types of nanoparticles, magnetic field strength, and inclination have small effects on LNN, but they have remarkable influences on the friction coefficients with positively correlated heat transfer rate, while the inclination is negatively correlated with heat transfer rate. The size of the nanoparticle shape factor is positively correlated with LNN. 相似文献
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Weijie Yu Qunsheng Peng Hongming Tu Zhangye Wang 《International Journal of Infrared and Millimeter Waves》1998,19(12):1661-1669
Most of current image synthesis models are based on optics of visible-spectrum. While simulating the illumination effect of visible light, they cannot show the infrared signature of the objects. This paper presents a synthesis model for generating realistic infrared images. We first establish a heat equilibrium equation of the object surface. Then according to it and the heat transfer inside the object and on the boundary surface of the object, we compute the temperature and radiometries of each surface patch of the object. Finally on the basis of the radiometries, each patch is drawn by Gouraud Shading. Experimental examples of the generated infrared images are presented, which illustrate the potential of our method. 相似文献
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In this paper, the effect of making swirling flow inside an annulus on the subcooled boiling heat transfer has been studied and discussed both experimentally and numerically. The Eulerian-Eulerian model and control volume technique have been used for numerical modeling of the problem. The experimental results show that the critical heat flux values are enhanced by making swirling flow. The experimental and numerical results also indicate that by making swirling flow inside the annulus, the subcooled boiling heat transfer coefficients are increased. Moreover, the experimental and numerical values of the boiling heat transfer coefficients show good agreement with each other. 相似文献
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Li Zhang James A. Bain Jian-Gang Zhu Leon Abelmann Takahiro Onoue 《Journal of magnetism and magnetic materials》2006
A method of heat-assisted magnetic recording (HAMR) potentially suitable for probe-based storage systems is characterized. In this work, field emission current from a scanning tunneling microscope (STM) tip is used as the heating source. Pulse voltages of 2–7 V were applied to a CoNi/Pt multilayered film fabricated on either bare silicon or oxidized silicon substrates. Different types of Ir/Pt and W STM tips were used in the experiment. The results show that thermally recorded magnetic marks are formed with a nearly uniform mark size of 170 nm on the film fabricated on bare silicon substrate when the pulse voltage is above a threshold voltage. The mark size becomes 260 nm when they are written on the identical film fabricated on an oxidized silicon substrate. The threshold voltage depends on the material work function of the tip, with W having a threshold voltage about 1 V lower than Pt. A synthesized model, which contains the calculation of the emission current, the simulation of heat transfer during heating, and the study of magnetic domain formation, was introduced to explain experimental results. The simulation agrees well with the experiments. 相似文献
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Valentin Roussellet Xiaodong Niu Hiroshi Yamaguchi & Fré dé ric Magoulé s 《advances in applied mathematics and mechanics.》2011,3(1):121-130
In this article, natural convection of a temperature-sensitive magnetic fluid
in a porous media is studied numerically by using lattice Boltzmann method. Results
show that the heat transfer decreases when the ball numbers increase. When the
magnetic field is increased, the heat transfer is enhanced; however, the average
wall Nusselt number increases at small ball numbers but decreases at large ball
numbers due to the induced flow being more likely confined near the bottom walls
with a high number of obstacles. 相似文献
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V. V. Kuznetsov O. V. Vitovsky S. V. Dimov S. A. Safonov S. P. Kozlov 《Journal of Engineering Thermophysics》2007,16(2):99-106
In this paper, experimental and numerical investigations of the hydrodynamics and heat transfer in a disk slot heat exchanger-reactor
for a radial flow of a gas mixture reacting on the channel walls are described. Data for the coefficients of heat transfer
from the wall being heated to the gas flowing inside the reactor are presented. The temperature field of a catalytically active
reactor plate at heat release on it has been investigated experimentally. Calculations of the flow and heat transfer in a
slot reactor element for a catalytic reaction with heat release have been performed. Partial oxidation of methane in an oxygen
medium with the formation of a hydrogen-containing synthesis gas in a two-dimensional microchannel has been investigated numerically.
Data for the extent of the chemical conversion of methane versus the initial mixture consumption and reaction temperature
are presented. 相似文献
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Effects of Hall current on a steady hydromagnetic (MHD) fully developed flow in a rotating environment within a parallel plate
channel in the presence of an inclined magnetic field is studied. From an extension of literature [13] subject to a forced
oscillation it is observed that the present paper is methodically more correct to work first in the steady state where forced
oscillation becomes insignificant and then new results are expected for an unsteady MHD flow under the influence of a pulse-oscillator.
Exact solutions of the governing equations are obtained in a closed form. The graphical representation for the velocity and
the induced magnetic field are depicted graphically and the heat transfer at both the plates are presented in tables. 相似文献
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为了了解勾形磁场对CdZnTe晶体生长质量的影响,利用有限元法对坩埚内的热量和动量传递过程进行了全局数值模拟。假定熔体和气相中的流动都为准稳态轴对称层流,研究了B_o(磁场轴线与晶体-坩埚界面的交点的磁场强度的轴向分量)为0 T,0.5 T,1.0 T,1.5 T,2.0 T,2.5 T,3.0 T时的CdZnTe晶体生长过程。结果表明:勾形磁场能有效抑制熔体内的流动,会产生由洛仑兹力、表面张力和浮力共同驱动的涡胞。随着磁场强度的增加,传热向导热型转变,熔体内最大流函数逐渐减小,抑制作用增强。 相似文献
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A bench for studying heat exchange between a pulsed spray and a surface heated to a temperature below the boiling point is
designed. A calorimeter to measure the integral heat exchange accurate to 1.5–3.0% and equipment generating the pulse spray
are described. The main parameters of the forming gas-drop-let flow (the gas and liquid velocities, the variation of the hydropulse
duration and the size of flow-constituting droplets when moving toward a heat exchanger, and the liquid concentration distribution
over the cross section and along the flow) and respective measuring techniques are given. It is shown that the duration of
a droplet train in the flow influences heat-and-mass transfer. 相似文献
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Maryamalsadat Lajvardi Jafar Moghimi-Rad Iraj Hadi Anwar Gavili Taghi Dallali Isfahani Fatemeh Zabihi Jamshid Sabbaghzadeh 《Journal of magnetism and magnetic materials》2010,322(21):3508-3513
This paper reports an experimental work on the convective heat transfer of ferrofluid flowing through a heated copper tube in the laminar regime in the presence of magnetic field. Significant enhancement on the heat transfer of ferrofluid by applying various orders of magnetic field is observed in this experiment. Also in this experiment, the effect of magnetic nanoparticles concentrations and magnet position have been investigated. The main reason for the enhancement of heat transfer coefficient could be caused due to remarkable changes in thermophysical properties of ferrofluid under the influence of applied magnetic field. 相似文献
19.
Potential profiles in the wake of a body in a plasma flow are presented for several values of a flow-aligned magnetic field. A transition from a potential "well" to a potential "hill" is found when the electron gyroradius becomes smaller than the size of the body transverse to the flow. 相似文献
20.
通过数值模拟及实验研究了润湿性及磁场对液态金属膜流流动状态的影响。首先,通过数值模拟研究了润湿性对膜流流动状态的影响。结果表明,当润湿性不好时,液态金属膜流容易发展为溪状流而不能完全覆盖底壁,入口膜厚较薄时更易发展为溪状流;在入口膜厚及其它情况相同时,密度越小越易发展为溪状流。其次,研究了磁场对膜流流动状态的影响。结果表明,槽道与流体润湿性不好时,有磁场情况下液态金属膜流覆盖底壁的区域较无磁场时增加,强磁场对膜流的湍流有抑制作用。最后,液态金属膜流实验结果表明,润湿性不好时,镓铟锡合金膜流容易收缩发展为溪状流,这与数值模拟的结果是一致的。上述研究结果对磁约束聚变堆液态第一壁的设计具有指导意义。 相似文献