流延法制备薄膜中的纳米流体流动传热解析研究

发布时间：2018-04-24 00:02

本文选题：Oldroyd-B流体 + 幂律流体　；参考：《北京建筑大学》2017年硕士论文

【摘要】：纳米薄膜的流动传热研究能够为优化材料加工工艺设计、改善产品性能提供理论指导。本文针对三种不同类型流体,分别研究了牛顿流体、粘弹性流体、幂律流体在拉伸平板上流动传热问题。研究工作如下:1)研究了拉伸平板上牛顿纳米流体的边界层流动传热问题,探讨了牛顿流体薄膜的表面张力梯度所引发的Marangoni效应,利用相似变换理论将偏微分方程组转化为非线性常微分方程组。通过同伦分析方法对方程组进行解析求解,通过打靶法对方程组进行数值求解,分析了边界层速度以及温度的分布特点,获得了各类物理参数对边界层速度、温度以及薄膜厚度的影响规律。2)建立了非稳态拉伸平板上Oldroyd-B流体的流动传热边界层控制模型,探讨了纳米粒子的加入对原有流体导热性能的影响。选取PVA水溶液为基液,加入Cu和Ag两种纳米粒子。通过相似变换将模型中偏微分方程组转化为四阶非线性常微分方程组,运用同伦分析方法得到解析近似解,分析了不稳定参数、普朗特数以及纳米粒子的体积分数对流体速度和温度的影响规律。3)研究了变壁温拉伸平板上幂律纳米流体薄膜的流动传热问题,根据非牛顿流体速度场粘性扩散与温度场热扩散比拟原理,重构幂律非牛顿流体傅里叶导热定律,探讨了变磁场、幂律速度滑移、幂函数壁面温度对流动传热的影响。选取熔融EVA作为基液,添加不同体积分数的Al2O3、Ti O2以及CuO纳米粒子。采用微分变换方法,结合牛顿迭代法(DTM-NIM)对方程组进行求解,获得各种参数对流体速度和温度分布的影响规律。本文所进行的理论分析和解析求解方法,为纳米流体薄膜的流动和传热研究奠定了基础。同时,通过与其他学者研究成果的比较,说明了文中所用两种解析方法的有效性,也为解决其他工程领域中的非线性微分方程问题提供了研究思路。
[Abstract]:The study of flow heat transfer of nanocrystalline films can provide theoretical guidance for optimizing material processing process design and improving product performance. In this paper, the flow heat transfer problems of Newtonian fluid, viscoelastic fluid and power-law fluid on a stretch plate are studied respectively for three different types of fluids. The research work is as follows: 1) the flow heat transfer problem of Newtonian nanoscale fluid on a stretch plate is studied, and the Marangoni effect caused by the surface tension gradient of Newtonian fluid film is discussed. The system of partial differential equations is transformed into nonlinear ordinary differential equations by using similarity transformation theory. The homotopy analysis method is used to solve the equations, and the target shooting method is used to numerically solve the equations. The distribution characteristics of boundary layer velocity and temperature are analyzed, and the physical parameters of the boundary layer velocity are obtained. The influence of temperature and film thickness on the flow heat transfer boundary layer control model of Oldroyd-B fluid on an unsteady tensile plate was established. The influence of the addition of nanoparticles on the thermal conductivity of the original fluid was discussed. PVA aqueous solution was selected as base solution and Cu and Ag nanoparticles were added. The partial differential equations in the model are transformed into fourth order nonlinear ordinary differential equations by similarity transformation. The analytical approximate solution is obtained by homotopy analysis method, and the unstable parameters are analyzed. The effects of Plantt number and volume fraction of nanoparticles on the velocity and temperature of the fluid are studied. According to the principle of viscous diffusion and thermal diffusion of non-Newtonian fluid velocity field, the Fourier law of thermal conduction of power law non-Newtonian fluid is reconstructed, and the influence of variable magnetic field, power law velocity slip and wall temperature of power function on flow heat transfer is discussed. Molten EVA was selected as base solution and Al _ 2O _ 3 TIO _ 2 and CuO nanoparticles with different volume fraction were added. The differential transformation method and Newton iterative method (DTM-NIMA) are used to solve the equations. The effects of various parameters on the velocity and temperature distribution of the fluid are obtained. The theoretical analysis and analytical solution in this paper lay a foundation for the study of flow and heat transfer in nanoscale fluid films. At the same time, by comparing with other scholars' research results, the effectiveness of the two analytical methods used in this paper is illustrated, and the research ideas for solving nonlinear differential equations in other engineering fields are also provided.
【学位授予单位】：北京建筑大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB383.2

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