微管道中纳米流体流动及传热研究

发布时间：2017-12-26 23:30

本文关键词：微管道中纳米流体流动及传热研究　出处：《内蒙古大学》2016年博士论文　论文类型：学位论文

【摘要】：近些年来,能源的开发及可持续利用问题正受到人们越来越多的关注.特别是在飞速发展的微型制造工艺和微细加工技术的影响下,微机电系统(MEMS)对热交换设备的换热性能也提出了更高的要求.纳米流体的诞生适应了这种发展的潮流,其改良的液体导热性能,显著地提高了系统的传热效率,而且流体本身不易发生粒子沉淀及对流道磨损和堵塞等问题,极大地拓展了其在工业领域中的应用.微流体系统本身具有特殊的微尺度效应、毛细效应、滑移效应、快速热传导效应等.基于这些不同的效应,微通道内流体运动的实现手段也有多种方式,例如利用压力、表面张力,电场力、磁场力、高频声波等.尤其是在当下迅速发展的电泳系统中,电渗流是占主导地位的驱动技术之一.由于电渗驱动具有高效率、易控性、且不会对机械构件造成破坏等优点,目前它被广泛的应用于生物、化学和医学等领域.流动电势同样可以引发微系统的电渗流动,而流动电势本身就是一种特殊的电渗现象.不同于普通的电渗流诱导机制,这种电渗流动不需要外部电场的介入.对于流动电势的研究相对成熟,无论在理论分析还是实验检验方面,都取得了丰富的成果.但是我们也看到,纳米流体在流动电势研究方面的报道还是很匮乏.同时,作为微流体有效驱动机制的磁场力即洛伦兹力被普遍应运于多种研究领域中,特别是在纳米流体的流动及传热问题中.在洛伦兹力的分析中,很多的研究工作都将电场的产生单纯视为流体运动与外加磁场的综合效应,而忽略了外部电场的应用.然而,外加电场同样会对微系统产生显著的影响.基于以上的分析,本文着重研究了流动电势作用下平行微管道及圆形微管道中纳米流体的流动与传热.进一步地分析了多场耦合作用下微管道内纳米流体的流动及传热机理.另外,我们考虑外部电场的情形下,探究了微管道中EMHD纳米流体的流动及热量传递问题.在本文的分析中,我们建立了双电层(EDL)及电场势所满足的Poisson-Boltzman方程,求解电场势分布,进而获得描述电场力的电荷密度分布.再将流动电势及电场力代入纳米流体所满足的修正动量及能量方程中,在不同边界条件下,解析求解了纳米流体流场的速度及温度分布,并获得了描述纳米流体热量传递的重要参数努赛尔数(Nusselt number)的解析表达.
[Abstract]:In recent years, problems of development and sustainable utilization of energy is more and more attention. Especially in the rapid development of micro manufacturing technology and micro machining technology, micro electro mechanical system (MEMS) on the heat transfer performance of heat exchange equipment is also put forward higher request. The birth of nano fluid to the development trend of liquid thermal conductivity improved, significantly improve the heat transfer efficiency of the system, and the fluid itself is not easy to happen particle precipitation and convection road wear and clogging problems, greatly expanding its application in the industrial field. The micro fluid system itself has the special effect of micro scale, capillary effect, slip effect, fast heat conduction effect. These different effects based on microchannel fluid motion means there are a variety of ways, such as the use of pressure, surface tension, electric field and magnetic field Force, high frequency sound waves. Especially in the current rapid development of electrophoresis system, the electroosmotic flow is one of the dominant driving technology. Due to electroosmotic driving with high efficiency, easy to control, and will not cause damage to mechanical components and other advantages, it has been widely used in biology, chemistry and medicine and other fields. Flow the potential can also initiate the electroosmotic flow in micro systems, and the potential flow itself is a kind of special phenomenon. Different from the electroosmotic electroosmotic flow induced mechanism, the electroosmotic flow does not require an external electric field. The intervention is relatively mature research for flow potential, both in theory or experiment, get rich results. But we also see that the reports of nanofluids in flow potential research is very scarce. At the same time, the magnetic force as the driving mechanism of the micro fluid force by Lorenz Generally applied in many research fields, especially in the flow and heat transfer problems of nanofluids. Analysis in Lorenz force, a lot of research work will produce electric field treated as a comprehensive effect of fluid motion and external magnetic field, while ignoring the application of an external electric field. However, the electric field will also have a significant the effect of micro system. Based on the above analysis, this paper focuses on the flow and heat transfer of nano fluid flow under the action of potential parallel micro channels and circular microchannels. Further analysis of the flow and heat transfer mechanism of micro channel flow meters extend under multi field coupling. In addition, we consider the external electric field situation to explore the EMHD nano fluid flow and heat transfer in microchannels. In this paper, we established the electric double layer (EDL) and the electric potential satisfy the Poisson-Boltzman equation, solution The potential distribution of the electric field, and then obtain the charge density distribution is described. The electric force correction of momentum and energy equation of flow potential and electric field force meet into nano fluids in under different boundary conditions, analytical solution of the velocity and temperature distribution of nano fluid flow, important parameters and won the description of Nu nano fluid heat transfer the number of (Nusselt number) of the analytical expression.
【学位授予单位】：内蒙古大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：O35

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