Effects of Velocity and Thermal Slip Conditions with Radiation on Heat Transfer Flow of Ferrofluids

To analyze the thermal convection of ferrofluid along a flat plate is the persistence of this study. The two-dimensional laminar, steady, incompressible flow past a flat plate subject to convective surface boundary condition, slip velocity in the presence of radiation has been studied where the magnetic field is applied in the transverse direction to the plate. Two different kinds of magnetic nanoparticles, magnetite Fe3O4 and cobalt ferrite CoFe2O4 are amalgamated within the base fluids water and kerosene. The effects of various physical aspects such as magnetic field, volume fraction, radiation and slip conditions on the flow and heat transfer characteristics are presented graphically and discussed. The effect of various dimensionless parameters on the skin friction coefficient and heat transfer rate are also tabulated. To investigate this particular problem, numerical computations are done using the implicit finite difference method based Keller-Box Method.

SHOCK SLIP-RELATIONS FOR THERMAL AND CHEMICAL NONEQUILIBRIUM FLOWS

This paper appears to be the first where the multi-temperature shock slip-relations for the thermal and chemical nonequilibrium flows are derived. The derivation is based on analysis of the influences of thermal nonequilibrium and viscous effects on the mass, momentum and energy flux balance relations at the shock wave. When the relaxation times for all internal energy modes tend to sere, the multi-temperature shock slip-relations are converted into single-temperature ones for thermal equilibrium hows. The present results can be applied to flows over vehicles of different geometries with or without angles of attack. In addition, the present single-temperature shock slip-relations are compared with those in the literature, and Some defects and limitations in the latter are clarified.

Unsteady MHD flow over exponentially stretching sheet with slip conditions

The present paper examines the hydromagnetic three-dimensional flow in- duced by a stretched surface. An incompressible material saturates the porous medium. Velocity and thermal slip boundary conditions are considered. Suitable transformations are used to obtain the nonlinear ordinary differential equations. Series solutions of the resulting systems are constructed. The effects of various pertinent parameters on the axial velocity and temperature distributions are analyzed graphically. The skin friction and the Nusselt number are computed numerically and graphically.

Effects of nonlinear velocity slip and temperature jump onpseudo-plastic power-law fluid over moving permeable surface in presence of magnetic field

Flow and heat transfer of a pseudo-plastic power-law fluid over a stretching permeable surface with the magnetic effect is investigated. In the boundary conditions,the nonlinear temperature jump and the velocity slip are considered. Semi-similarity equations are obtained and solved by bvp4c with MATLAB. The problem can be considered as an extension of the previous work done by Mahmoud(Mahmoud, M. A. A. Slip velocity effect on a non-Newtonian power-law fluid over a moving permeable surface with heat generation. Mathematical and Computer Modelling, 54, 1228–1237(2011)). Efforts are made to discuss the effects of the power-law number, slip velocity, and temperature jump on the dimensionless velocity and temperature distribution.

Upshot of ohmically dissipated Darcy-Forchheimer slip flow of magnetohydrodynamic Sutterby fluid over radiating linearly stretched surface in view of Cash and Carp method

The present work concerns the momentum and heat transmission of the electro-magnetohydrodynamic (E-MHD) boundary layer Darcy-Forchheimer flow of a Sutterby fluid over a linear stretching sheet with slip. The nonlinear equations for the proposed model are analyzed numerically. Suitable techniques are used to transform the coupled nonlinear partial differential equations (PDEs) conforming to the forced balance law, energy, and concentration equations into a nonlinear coupled system of ordinary differential equations (ODEs). Numerical solutions of the transformed nonlinear system are obtained using a shooting method, improved by the Cash and Carp coefficients. The influence of important physical variables on the velocity, the temperature, the heat flux coefficient, and the skin-friction coefficient is verified and analyzed through graphs and tables. From the comprehensive analysis of the present work, it is concluded that by intensifying the magnitude of the Hartmann number, the momentum distribution decays, whereas the thermal profile of fluid increases. Furthermore, it is also shown that by aug- menting the values of the momentum slip parameter, the velocity profile diminishes. It is found that the Sutterby fluid model shows shear thickening and shear thinning behaviors. The momentum profile shows that the magnitude of velocity for the shear thickening case is dominant as compared with the shear thinning case. It is also demonstrated that the Sutterby fluid model reduces to a Newtonian model by fixing the fluid parameter to zero. In view of the limiting case, it is established that the surface drag in the case of the Sutterby model shows a trifling pattern as compared with the classical case.

基于多个热成像探头传感器的滑环装置碳刷温度监测与分析

文章设计了一款基于多个热成像探头传感器的滑环装置碳刷温度监测系统,该系统利用热成像探头传感器来获取碳刷的温度数据,并通过数据处理和分析,实现对碳刷温度的监测和报警。系统采用热成像视频监测,增加现地显示装置,通过对系统进行设计,实现了历史数据查询、故障预警等多种功能,可更好地保障水利发电的安全运行。

Effect of Improving the Slip Properties of the Organic Materials on the Inorganic Filler in Heat Dissipated Pad

The heat dissipated pad is made of composite mixing silicon or epoxy resin with thermal conductive inorganic fillers. The heat-dissipation material improves performance as the amount of thermal conductivity filler increases. However, the optimum recipe should be determined by considering the price and pad formability. In this study, high performance thermal pad is made of silicon resin mixed with Al2O3 as a thermally conductive filler. Since Al2O3 is low cost, it can use much filler. Al2O3 has improved slip-ability with organic coating on it to increase the viscosity of the slurry. The same process and the same recipe, could maximize the amount of the filler. As a result, the thermal conductivity is lower by 10%. But the viscosity is reduced by 60%, too. So form-ability is getting priority.

两层热对流系统传热与流动结构的实验

双层热对流系统广泛存在于自然界中。为研究该系统的传热规律,刻画其中的流动结构特性,在矩形对流槽中使用甘油和2 cs硅油两种互不相溶的液体作为工作介质。位于底部的甘油液体层宽高比为10.4,其下表面是无滑移固液边界,上表面为滑移交界面,底部甘油层的实验参数为Rayleigh数范围260≤Ra 1≤6000,Prandtl数范围3708<Pr_(1)<7000。硅油液体层的宽高比约为0.53,上表面为无滑移固液边界,硅油层Rayleigh数范围1.5×10^(9)≤Ra_(2)≤2.0×10^(10),Prandtl数范围28<Pr_(2)<33。发现两层对流系统在两个区间内有不同的传热效率和流动状态。在区间1,即传热功率小于某个特定热流时,下面甘油层处于稳定层流状态。而在区间2,即传热功率大于该热流时,甘油层内液体处于不稳定对流状态。随着全局温差的增加,两层热对流系统的全局传热效率从区间1到区间2有一个突然的增加。甘油层的振荡失稳临界Rayleigh数为1523,这个数值小于无限大平板无滑移边界的理论预测值1708,即滑移边界可使流体更不稳定,并使得硅油层的传热效率增加。采用阴影法对该系统内的对流斑图、交界面以及热羽流等流动结构进行了进一步刻画和分析。

界面速度与温度滑移对有限长线接触纯滑动热弹流接触的影响

随着表面工程技术的发展,润滑界面发生滑移的现象已比较常见.除了发生界面速度滑移,在有显著温升的弹流接触界面也有可能发生温度滑移.本研究在有限长线接触纯滑动热弹流润滑问题的基础上,建立了4种界面滑移模型,采用数值分析方法,揭示了在运动和静止表面分别发生速度和温度滑移时接触区润滑特性的变化.研究发现,运动表面的速度滑移会阻碍接触区的润滑油流动,而静止表面的速度滑移则促进润滑油流动;运动表面的温度滑移会降低接触区内的温升,静止表面的温度滑移则会显著增加接触区的温升并降低摩擦系数.速度和温度滑移都可能将摩擦系数降到0.01以下,实现超滑,但静止表面的温度滑移对摩擦系数的影响更为显著.

石墨烯微通道的流动传热数值模拟

为提高微通道散热器的传热性能,笔者采用在流道内壁涂覆石墨烯的方法对微通道的传热效率进行了优化。通过将分子动力学(Molecular Dynamics, MD)模拟与计算流体力学(Computational Fluid Dynamics, CFD)相结合,研究了入口流速、通道长度对石墨烯微通道和普通微通道的固液界面总传热率的影响。结果表明:石墨烯的引入使流体分子相对壁面产生了滑移,增大了流动的平均速度,降低了流体分子间的速度差异性;使用石墨烯涂层和增大入口流速均可大幅提高界面传热能力;相比于普通微通道,石墨烯微通道的传热率最高提升了49%,最高平均热流密度可达730 W/cm^(2);界面总传热率随通道长度的增大而提高,最终达到其最大值并趋于稳定。研究结果对于高性能微通道散热器的设计有一定的参考价值。

螺旋管内天然气冷凝流动传热数值模拟

针对螺旋管内天然气混合工质冷凝过程,在Lee模型的基础上,引入温度滑移因子,提出一种变温相变新模型,分别用新模型和Lee模型进行不同压力工况下的冷凝流动换热模拟。结果表明,新模型计算得到的温度沿流动方向下降很明显,反映了天然气温度滑移的影响,可以更好地反映出实际天然气冷凝过程中的物性变化,气液两相分布图中可明显观测到二次流扰动现象。为了同时考虑质量扩散热阻的影响,用Silver方法修正了新模型的模拟结果,修正后平均传热系数值与试验测定值的误差在10.7%~14%,预测精度优于Lee模型25%的误差精度。修正后的变温相变新模型适用于螺旋管内天然气混合工质的冷凝流动传热计算。

连续配筋混凝土路面温度应力分析

根据钢筋混凝土间粘结滑移的线性本构关系 ,建立了连续配筋混凝土路面 (CRCP)温度应力分析的计算模型及微分平衡方程 ,求出了微分方程的解答 ,并分析了降温荷载作用下路面内应力、位移的分布规律及裂缝间距、配筋率与配筋方式等计算参数的影响 ,给出了不利位置处钢筋和混凝土应力、位移的解析表达式。结果表明 ,本文方法可以方便有效地分析 CRCP的温度应力。

端面微尺度效应和热黏效应对干气密封性能的影响

考虑干气密封环端面微尺度效应及气膜的热黏效应,基于气体多变过程理论和气体润滑理论,对可压缩流体条件下的扩展平均雷诺方程进行修正,并应用有限元法进行求解;通过改变密封的操作参数,分析研究了端面微尺度效应和热黏效应对干气密封性能的影响规律。结果表明,干气密封在正常工作状态下,压力的升高使气体滑移流和表面粗糙度之间的耦合效应减弱,对泄漏率有固定的影响。若量纲1膜厚Hs<3.5,应考虑表面粗糙度对密封性能的影响;当逆Knudsen数B≥21或Knudsen数Kn≤0.0476时,可忽略气体滑移流效应的影响;热黏效应和表面粗糙度能提高密封动压效应,降低泄漏率,而气体滑移流效应却使泄漏率增大,端面承载能力降低;在低速高压下,表面粗糙度比滑移流效应对密封性能的影响大;当外压po≥2.02MPa时,热黏效应在对密封性能影响中占主导地位。

考虑黏结滑移关系的连续道床板伸缩刚度计算方法

连续道床板在降温和自身收缩情况下容易出现裂缝,从而造成伸缩刚度的折减,不同裂缝间距时的伸缩刚度差别很大,而伸缩刚度又是连续道床板温度力计算的重要参数。考虑钢筋与混凝土间的黏结滑移关系,建立一种连续道床板伸缩刚度计算方法,对不同裂缝间距情况下的钢筋和混凝土应力、黏结阻力以及伸缩刚度进行研究,对黏结阻力型式、混凝土强度等级和配筋率对伸缩刚度的影响进行参数研究。研究结果表明:即使在一定的裂缝间距情况下,伸缩刚度也并非一定值,而是随荷载增大而逐渐降低的变量,混凝土强度等级对伸缩刚度折减的影响较小,配筋率影响较大,检算过程中可根据裂缝间距增加一定的边界条件即可得到不同温度条件下的应力与刚度分布。

位错热激活滑移的数值模拟

在三维离散位错动力学模型中,用Langevin力描述温度对位错的影响作用,模拟了位错克服晶格Peierls应力与阻尼应力的滑移过程.模拟结果表明,位错克服Peierls应力的热激活效应随温度的升高而增大,随应变率的增高而减小.利用热激活本构模型描述了位错热激活滑移过程,拟合了Peierls应力的激活能,结果表明含温度的离散位错动力学模型能较正确地模拟位错的热激活滑移过程.但Peierls阻碍的非离散化处理使激活能与指前因子均随温度升高而增大,这表明离散位错动力学模型模拟Peierls阻碍存在不足之处,其本质原因是介观级的位错动力学模型目前还无法正确模拟微观级的位错芯性质.

Effects of Thermal Radiation and Slip Mechanism on Mixed Convection Flow of Williamson Nanofluid Over an Inclined Stretching Cylinder

The current investigation highlights the mixed convection slip flow and radiative heat transport of uniformly electrically conducting Williamson nanofluid yield by an inclined circular cylinder in the presence of Brownian motion and thermophoresis parameter.A Lorentzian magnetic body force model is employed and magnetic induction effects are neglected.The governing equations are reduced to a system of nonlinear ordinary differential equations with associated boundary conditions by applying scaling group transformations.The reduced nonlinear ordinary differential equations are then solved numerically by Runge-Kutta-Fehlberg fifth-order method with shooting technique.The effects of magnetic field,Prandtl number,mixed convection parameter,buoyancy ratio parameter,Brownian motion parameter,thermophoresis parameter,heat generation/absorption parameter,mass transfer parameter,radiation parameter and Schmidt number on the skin friction coefficient and local Nusselt are analyzed and discussed.It is found that the velocity of the fluid decreases with decrease in curvature parameter,whereas it increases with mixed convection parameter.Further,the local Nusselt number decreases with an increase in the radiation parameter.The numerical comparison is also presented with the existing published results and found that the present results are in excellent agreement which also confirms the validity of the present methodology.

Effects of velocity and thermal wall slip on magnetohydrodynamics(MHD)boundary layer viscous flow and heat transfer of a nanofluid over a non-linearly-stretching sheet:a numerical study

In this analysis,the boundary layer viscous flow of nanofluids and heat transfer over a non-linearly-stretching sheet in the presence of a magnetic field is presented.Velocity and thermal slip conditions are considered instead of no slip conditions at the boundary.A similarity transformation set is used to transform the governing partial differential equations into non-linear ordinary differential equations.The reduced equations are solved numerically using the Keller box method.The influence of the governing parameters on the dimensionless velocity,temperature,nanoparticle concentration as well as the skin friction coefficient,Nusselt number,and local Sherwood number are analyzed.It is found that as the velocity slip parameter increases,the velocity profile is decreased and the skin friction and heat transfer decreased while the mass transfer is increased.Increasing the thermal slip parameter causes decreases in the heat and mass transfer rates.The results are presented in both graphical and tabular forms.

塔里木盆地顺北油气田地温场对奥陶系超深层油气的影响——以顺北5号走滑断裂带为例

塔里木盆地顺北油气田走滑断裂带奥陶系超深层油气资源类型、油气性质呈现规律性变化,油气分布规律主控因素不清制约了资源类型与勘探序列评价。为研究温度场对深层油气的影响,开展了顺北5号断裂带现今实测温度资料统计分析、关键成藏期热史恢复、烃源岩热演化与奥陶系油气性质和油气成熟度对应关系研究。结果表明,顺北地区现今地温场纵向上呈现由浅层向深层地温梯度逐渐降低的特征,寒武系玉尔吐斯组烃源岩的现今地温和关键成藏期古地温均呈现由北往南逐渐升高的特征。在超深层低地温梯度背景下,顺北奥陶系超深层油藏温度未达到原油大量裂解温度窗,为液态石油的保存提供了有利条件;在关键成藏期——海西晚期,本地寒武系玉尔吐斯组烃源岩由北往南热演化程度逐渐增加,在高压抑制生烃演化作用下,顺北5号断裂带北段和中段以生油阶段为主,南段开始以生凝析油气阶段为主,演化产物与现今奥陶系超深层油气藏类型、原油密度、天然气干燥系数、生产气油比、油气热演化程度平面分布特征具有较好一致性,指示地温场控制下的烃源岩热演化差异是资源类型和油气性质差异分布的主要影响因素。

热耗散下螺旋槽干气密封气膜刚度的计算与分析

通过二阶非线性滑移边界条件下的雷诺方程并用PH线性化方法和迭代法求得螺旋槽内的气膜推力和气膜压力,并推导了其气膜厚度,得到二阶非线性滑移边界条件下气膜刚度的近似解析式,推导出考虑热耗散下的气膜能量微分方程;利用气膜的压力、能量方程、二阶非线性滑移边界条件下气膜刚度的近似解析式,通过Matlab软件求得螺旋槽内气膜刚度在不同压力、转速、槽深、螺旋角下的分布。结果表明:随着压力、转速、槽深的增大,气膜刚度随之增大,并在槽根部附近达到最大值,且气膜刚度的变化呈非线性;在槽深为6μm、介质压力为0.4MPa、转速为8700r·min-1、环境压力为101.3k Pa的工况下,螺旋角为75°左右时,气膜刚度最大。通过本文设计的在不同介质压力下的试验表明,通过能量微分方程计算所得的考虑热耗散下的气膜刚度数值比不考虑热耗散的气膜刚度数值更接近试验值。本文结果对优化干气密封结构参数、提升干气密封性能十分重要。

川藏铁路成康段活动断裂工程效应及地质选线

研究目的:川藏铁路成都至康定段位于我国西部著名的"Y"字型构造楔合部位,区域构造复杂,新构造运动活跃,分布有龙门山断裂、鲜水河断裂和玉农希断裂三条全新世活动断裂,断裂活动对该区铁路选线所造成重大影响。本文通过研究三条活动断裂的粘滑位错、蠕滑变形特征,强震破坏特征以及活动断裂导致的热害、次生灾害分布情况,来探讨在此类地质条件复杂区域的地质选线原则,从而降低活动断裂对铁路工程的破坏。研究结论:(1)川藏铁路成康段穿越的三条断裂均发生过强烈地震,断裂活动性强,对铁路选线影响较大,需通过合理选线降低风险;(2)活动断裂导致的工程效应有地表破裂导致工程破坏,地震波导致震动破坏,断裂控制区地热异常导致工程施工难度加大或工程方案不可行,断裂活动形成的次生灾害如滑坡、泥石流、崩塌等对工程造成破坏;(3)活动断裂区地质选线应充分考虑活动断裂的活动特征以及其导致的主要工程问题;(4)本研究成果主要应用于川藏铁路成康段地质选线工作。