带扰流结构的微通道流动与传热数值研究

发布时间：2018-08-18 14:48

【摘要】：近十多年以来,微机电系统技术和纳米技术得到了空前的发展,人类正从米、厘米的宏观世界朝着微米、纳米的微观世界的道路上走下去,作为微机电系统技术的一个重要分支——微流体技术,在近些年来,也已经有了很大的发展,取得了可观的进步。在新的时代里,电子元器件微小化是必然趋势。这些随着时代应运而生的微型电子元器件改变了人类的生活方式,从此进入“微时代”。随着现代电子元器件集成程度越来越高的这种趋势,各种电子元器件的功率越来越高、局部的热流密度越来越大,而导致这些集成化元器件失效的重要原因是,其工作时温度过高,不能准确有效地运行。于是微尺度下的流动和传热的问题就日益突出,并逐渐成为这些科学技术领域迈向更高台阶进一步发展的瓶颈。而微尺度加工技术的迅速发展的今天,使得电子元器件的体积越来越微小,重量越来越轻,功能越来越强大,集成度越来越高,为解决微尺度换热问题提供了良好的先决条件,微尺度科学在现代科学技术中逐渐成为研究的前沿。在科学技术飞速发展的今天,微尺度领域里传热、散热也成了亟待突破的难题。于是,这就给散热技术提出了更高的要求,而针对这种高集成电子元器件,微通道散热是最理想、最有效的方式,也是在散热领域里的一个重要发展方向。本文开展了对微通道散热的理论研究,并建立了带扰流结构的微通道的模型,以及传统长直微通道模型,和相应的研究方法。通过研究传统长直微通道在均匀热载荷下的温度分布以及换热效率,分析其结果并对传统长直微通道方案的基础行加以改进,其具体的实施方案是在传统长直微通道的基础上,增添了结构简单的障碍物即扰流结构,这种带扰流结构的微通道的强化传热的机理是利用障碍物使流体产生径向流动,从而加强微通道内流体的混合,并使流体在通道内流动的时候形成扰流漩涡,从而破坏流体流动的边界层,同时扰动的流体可以获得较高的对流传热系数,增强流体与微通道壁面之间的换热效率。接着研究了扰流肋片的疏密程度对换热的影响,分别对相同长度段的微通道设置了4肋片跟6肋片两种不同情况,计算得到其温度分布云图,分析对比得到结论。然后研究了入口速度对微通道换热的影响,分别设置了5个不同的入口速度,计算其速度场,温度场,压力场,最终分析得出结论。本文的研究方法是应用ANYSY CFD ICEM软件建立带扰流结构的微通道以及传统长直微通道的二维模型,然后将模型分别导入FLUENT软件中进行定义固体材料以及流体属性的前处理,然后并选择SIMPLE算法计算在均匀热流量载荷的条件下,分别模拟计算传统长直微通道与带扰流结构的微通道流体流动情况,研究了不同疏密程度的扰流肋片进行计算分析对比。然后设置不同的入口速度进行计算,将得到的温度分布云图、压力场、速度矢量图、热源处温度分布图以及流固交界面温度分布图进行对比,最终分析得出的结论是:(1)随着入口速度增大,雷诺数增大,压降也随之增大,即所须提供微通道流体流动的输送动力增加。(2)对于已经确定以水为工质的微通道内,微通道的换热能力随着流体流速的增大而增强,当入口流体流速增大到一定程度是,换热能力维持在一个稳定的水平。所以在一定的范围内,可以通过增大流体速度,已达到增强换热效果的目的。(3)当给定微通道的尺寸,微通道的换热量随着雷诺数的增大而增大;当增到的一定程度时,微通道的换热量也逐渐趋于平稳,即换热效果维持不变。
[Abstract]:In the past ten years, micro-electro-mechanical system technology and nano-technology have made unprecedented development. Human beings are moving from the macro-world of meter and centimeter to the micro-world of micron and nano. As an important branch of micro-electro-mechanical system technology, micro-fluid technology has also made great progress in recent years and has made great progress. Considerable progress has been made. In the new era, the miniaturization of electronic components is an inevitable trend. These micro-electronic components have changed the way of life of human beings and entered the "micro-era". The local heat flux density is getting higher and higher, and the main reason for the failure of these integrated components is that the working temperature is too high to operate accurately and effectively. With the rapid development of processing technology, electronic components are becoming smaller and smaller in size, lighter and lighter in weight, more powerful in function and higher in integration, which provides a good prerequisite for solving the problem of micro-scale heat transfer. Micro-scale science has gradually become the forefront of research in modern science and technology. Nowadays, heat transfer and heat dissipation in the field of micro-scale have become a problem to be solved urgently. Therefore, higher requirements have been put forward for heat dissipation technology. For this kind of high-integrated electronic components, micro-channel heat dissipation is the most ideal and effective way, and it is also an important development direction in the field of heat dissipation. The theoretical study of heat dissipation is carried out, and the model of microchannel with turbulent structure, the traditional long straight microchannel model and the corresponding research methods are established. Based on the traditional long straight microchannel, a simple obstruction is added, i.e. a turbulent structure. The mechanism of enhanced heat transfer in this microchannel with turbulent structure is to use the obstruction to make the fluid flow radially, thereby enhancing the mixing of the fluid in the microchannel and causing the fluid to become disturbed when flowing in the microchannel. The turbulent fluid can obtain higher convective heat transfer coefficient and enhance the heat transfer efficiency between the fluid and the microchannel wall. Then the influence of fin density on the heat transfer is studied. Four fins and six fins are set in the same length microchannel respectively. Then the influence of inlet velocity on heat transfer in microchannels is studied. Five different inlet velocities are set up to calculate the velocity field, temperature field and pressure field. Finally, the conclusion is drawn. The research method of this paper is to use ANYSY CFD ICEM software to establish the structure with turbulence. The two-dimensional models of microchannel and traditional long straight microchannel are imported into FLUENT software to pre-process the definitions of solid materials and fluid properties, and then SIMPLE algorithm is selected to calculate the fluid flow in microchannel under uniform heat flux load. Then, different inlet velocities are set to calculate and compare the temperature distribution nephogram, pressure field, velocity vector diagram, temperature distribution diagram at the heat source and temperature distribution diagram at the fluid-solid interface. When the velocity increases, the Reynolds number increases, and the pressure drop increases, that is, the conveying power of the fluid flow in the microchannel is increased. In a certain range, the effect of heat transfer can be enhanced by increasing the fluid velocity. (3) When the size of the microchannel is given, the heat transfer of the microchannel increases with the increase of Reynolds number; when the increase is to a certain extent, the heat transfer of the microchannel becomes stable gradually, that is, the effect of heat transfer remains unchanged.
【学位授予单位】：武汉工程大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TK124

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