共查询到20条相似文献,搜索用时 15 毫秒
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A three-dimensional mathematical model is developed to examine the flow of nonlinear thermal radiation Oldroyd-B nanofluid past a bidirectional linearly stretched surface in a porous medium. The flow is induced by temperature dependent thermal conductivity, chemical reaction and convective heat and mass conditions. Novel characteristics of Brownian motion and thermophoresis are accompanied by magnetohydrodynamic and heat generation/absorption. Self-similar transformations are employed to convert the system of nonlinear partial differential equations to a system of ordinary differential equations with high nonlinearity and are solved by strong analytic technique named as Homotopy Analysis method (HAM). Effects of varied arising parameters on involved distributions are reflected through graphical illustrations. From this study, it is perceived that strong magnetic field hinders the fluid's motion and leads to rise in temperature that eventually lowers heat transfer rate from the surface. Further, decrease in heat transfer rate is also observed for enhanced values of thermal radiation parameter. To validate our results, a comparison with already published paper in limiting case is also given and results are found in excellent oncurrence; hence reliable results are being presented. 相似文献
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Non-Newtonian fluid model for blood flow through a tapered artery with a stenosis and variable viscosity by modeling blood as Jeffrey fluid has been studied in this paper.The Jeffrey fluid has two parameters,the relaxation time λ1 and retardation time λ2.The governing equations are simplified using the case of mild stenosis.Perturbation method is used to solve the resulting equations.The effects of non-Newtonian nature of blood on velocity profile,temperature profile,wall shear stress,shearing stress at the stenotsis throat and impedance of the artery are discussed.The results for Newtonian fluid are obtained as special case from this model. 相似文献
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A novel microchannel heat sink with oval-shaped micro pin fins (MOPF) is proposed and the characteristics of fluid flow and heat transfer are studied numerically for Reynolds number (Re) ranging from 157 to 668. In order to study the influence of geometry on flow and heat transfer characteristics, three non-dimensional variables are defined, such as the fin axial length ratio (α), width ratio (β), and height ratio (γ). The thermal enhancement factor (η) is adopted as an evaluation criterion to evaluate the best comprehensive thermal-hydraulic performance of MOPF. Results indicate that the oval-shaped pin fins in the microchannel can effectively prevent the rise of heat surface temperature along the flow direction, which improves the temperature distribution uniformity. In addition, results show that for the studied Reynolds number range and microchannel geometries in this paper, the thermal enhancement factor η increases firstly and then decreases with the increase of α and β. In addition, except for Re = 157, η decreases first and then increases with the increase of the fin height ratio γ. The thermal enhancement factor for MOPF with α = 4, β = 0.3, and γ = 0.5 achieves 1.56 at Re = 668. The results can provide a theoretical basis for the design of a microchannel heat exchanger. 相似文献
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The flow and convective heat transfer characteristics under different heating loads in micro-pin-fins of circle, diamond and triangle are experimentally investigated with Reynolds number ranging from 0–1,000. The pressure drops, friction factors, thermal resistance and Nusselt number in micro-pin-fins with different cross-section shapes are obtained when the heating load changes from 50 to 150 W. Basing on the experimental results, the mechanisms of the influence of heating load on the resistance and heat transfer characteristics in micro-pin-fins with different cross-section shapes are detailed analysed. It is found that pressure drops in three types of micro-pin-fins all become large with the increase of the heating load, and the change of pressure drop in triangular micro-pin-fins is larger than those in the other two micro-pin-fins. At low Re, the friction factors in the three types of micro-pin-fins become large with the increase of the heating load, but this phenomenon disappears when Re>400 for the circle and diamond micro-pin-fins, and Re>250 for the triangular micro-pin-fins. The convective heat transfer in micro-pin-fins with cross-section shapes of circle, diamond and is enhanced by increasing the heating load, but the convective heat transfer coefficients and Nu in the triangular micro-pin-fins becomes slightly smaller when Re>250. 相似文献
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This communication addresses the impact of heat source/sink along with mixed convection on oblique flow of Casson fluid having variable viscosity. Similarity analysis has been utilized to model governing equations, which are simplified to set of nonlinear differential equations. Computational procedure of shooting algorithm along with 4th order Range-Kutta-Fehlberg scheme is opted to attain the velocity and temperature distributions. Impact of imperative parameters on Casson fluid flow, temperature, significant physical quantities such as skin friction, local heat flux and streamlines are displayed via graphs. 相似文献
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Mixed Convection Heat and Mass Transfer in a Micropolar Fluid with Soret and Dufour Effects 下载免费PDF全文
A mathematical model for the steady, mixed convection heat and mass
transfer along a semi-infinite vertical plate embedded in a micropolar
fluid in the presence of Soret and Dufour effects is presented. The
non-linear governing equations and their associated boundary conditions
are initially cast into dimensionless forms using local similarity
transformations. The resulting system of equations is then solved
numerically using the Keller-box method. The numerical results are
compared and found to be in good agreement with previously published
results as special cases of the present investigation. The non-dimensional
velocity, microrotation, temperature and concentration profiles are
displayed graphically for different values of coupling number, Soret
and Dufour numbers. In addition, the skin-friction coefficient, the
Nusselt number and Sherwood number are shown in a tabular form. 相似文献
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In this article we investigate the flow of Sutterby liquid due to rotating stretchable disk. Mass and heat transport are analyzed through Brownian diffusion and thermophoresis. Further the effects of magnetic field, chemical reaction and heat source are also accounted. We employ transformation procedure to obtain a system of nonlinear ODE's. This system is numerically solved by Built-in-Shooting method. Impacts of different involved parameter on velocity, temperature and concentration are described. Velocity, concentration and temperature gradients are numerically computed. Obtained results show that velocity is reduced through material parameter. Temperature and concentration are enhanced with thermophoresis parameter. 相似文献
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The secondary flow driven by the primary vortex in a cylinder,generating the so called "tea leaf paradox",is fundamental for understanding many natural phenomena,industrial applications and scientific researches.In this work,the effect of wettability on the primary vortex and secondary flow is investigated by the three-dimensional multiphase lattice Boltzmann method based on a chemical potential.We find that the surface wettability strongly affects the shape of the primary vortex.With the increase of the contact angle of the cylinder,the sectional plane of the primary vortex gradually changes from a steep valley into a saddle with two raised parts.Because the surface friction is reduced correspondingly,the core of the secondary vortex moves to the centerline of the cylinder and the vortex intensity also increases.The stirring force has stronger effects to enhance the secondary flow and push the vortex up than the surface wettability.Interestingly,a small secondary vortex is discovered near the three-phase contact line when the surface has a moderate wettability,owing to the interaction between the secondary flow and the curved gas/liquid interface. 相似文献
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对流动分岔后的超临界二氧化碳在平面对称突扩管中进行强迫对流换热进行了数值模拟,研究了热流密度在流体发生流动分岔现象后流动特性的影响。计算结果表明:随着热流密度的增加,临界雷诺数和转换雷诺数减小,流动稳定性遭到削弱;对应于相同的雷诺数,由于流动分岔引起的不对称压力分布随着热流密度的增加对应于突扩管上、下半部有不同变化规律,这使得对应回流区的大小分别减小和增大。 相似文献
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This article presents the experimental results of an evaluation of the influence of internal flow patterns on the heat transfer performance of a closed-loop oscillating heat pipe with check valves. It was found that the internal flow patterns could be classified according to four flow patterns: dispersed bubble flow, bubble flow, slug flow, and annular flow, respectively. The main regime of each flow pattern can be determined from a flow pattern map. The map can be used to predict the trend of the heat transfer rate in the closed-loop oscillating heat pipe with check valves. 相似文献
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随着高效预冷器在航天航空领域发挥越来越重要的作用,紧凑高效换热器的研究成为了人们关注的热点。本文基于紧凑微通道换热器的几何特征,针对矩形截面平行流道换热器内超临界压力低温流体(氢和氦)在大温差条件下的流动换热现象进行数值模拟研究。通道截面边长小于1 mm,热流体氦和冷流体氢的进出口温差均大于600 K。通道内流体换热系数在顺流和逆流条件下有不同的变化趋势,并出现峰值。换热量随着通道宽度的增大而增大,流动压降随着通道宽度的增大而减小。冷热流体逆流时换热量大,压降较小,但对换热器材料要求较高。 相似文献
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随着高效预冷器在航天航空领域发挥越来越重要的作用,紧凑高效换热器的研究成为了人们关注的热点。本文基于紧凑微通道换热器的几何特征,针对矩形截面平行流道换热器内超临界压力低温流体(氢和氦)在大温差条件下的流动换热现象进行数值模拟研究。通道截面边长小于1 mm,热流体氦和冷流体氢的进出口温差均大于600 K。通道内流体换热系数在顺流和逆流条件下有不同的变化趋势,并出现峰值。换热量随着通道宽度的增大而增大,流动压降随着通道宽度的增大而减小。冷热流体逆流时换热量大,压降较小,但对换热器材料要求较高。 相似文献
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Mixed Convection in Viscoelastic Boundary Layer Flow and Heat Transfer over a Stretching Sheet 下载免费PDF全文
Antonio Mastroberardino 《advances in applied mathematics and mechanics.》2014,6(3):359-375
An investigation is carried out on mixed convection boundary layer flow of an incompressible
and electrically conducting viscoelastic fluid over a linearly stretching surface in which the
heat transfer includes the effects of viscous dissipation, elastic deformation,
thermal radiation, and non-uniform heat source/sink for two general types of
non-isothermal boundary conditions. The governing partial differential equations for
the fluid flow and temperature are reduced to a nonlinear system of ordinary differential
equations which are solved analytically using the homotopy analysis method (HAM).
Graphical and numerical demonstrations of the convergence of the HAM solutions are provided,
and the effects of various parameters on the skin friction coefficient and wall heat
transfer are tabulated. In addition, it is demonstrated that previously reported solutions of the
thermal energy equation given in [1] do not converge at the boundary, and therefore,
the boundary derivatives reported are not correct. 相似文献