Numerical Simulation of Microtube Flows with Temperature Effect

• Main Authors: Shu-Kang Chang, 張書綱
• Other Authors: Ching-Shung Chen
• Format: Others
• Language: zh-TW
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/67550538256608708504

碩士 === 淡江大學 === 航空太空工程學系碩士班 === 94 === The objective of this research is to use numerical simulation program to analyze fluid mechanics and heat transfer characteristics in three dimensional micro-tubes of incompressible water-liquid. Three dimensional micro-tubes simplified into two dimensional axis-symmetric of x-r plane field is to facilitate the computing process of the program, and then only the boundary-layer equation needs estimating. Because this equation has the character of parabolic type in mathematics, it could provide a very accurate and powerful tool for computing fluid mechanics and heat transfer characteristics in micro-tubes after fully developed region. At the time being, comparing with the general computer devices, simulating the program is much faster than the traditional Navier-Stokes equation hundreds of times. The scholars in the references said that there are usually some differences in measurement and analysis between different experiments and numerical analysis. All of these main influences are due to temperature effects, compressibility effects, rarefaction effects, viscous dissipation effects, Electro-osmotic effects, channel surface conditions, experiment errors and so on. Therefore, temperature effects are considered the main point in the research. Because of the change of temperature, the basic physical properties in fluid, such as density, conductivity and viscosity, will be affected. If temperature changes, they change, and even directly affect the differences of pressure, velocity and temperature in the flow field by considering temperature effects or not. For thermal boundary condition, it divides into isothermal wall temperature and constant heat flux on the wall in micro-tubes. Under discussing two parts of thermal boundary condition, to investigate Nusselt number and the relationship between friction factor and Reynolds number first, and then verify with heat transfer characteristics of traditional size. According to the values of Nusselt number and f*Re from the program, the contracting error is very small with experimental formula of traditional size. This verification means that the research in using boundary-layer equation with micro-tubes simulating analysis, is truly an accurate numerical simulation equation. Without temperature effects, all the values of Nusselt number and f*Re would conform to fluid mechanics and heat transfer characteristics in traditional size; but if considering temperature effects, Nusselt number would be higher than traditional heat transfer characteristics, and f*Re would raise following to the increasing diameter. Besides, this research also discusses the fluid mechanics and heat transfer characteristics in different diameter and Reynolds number in micro-tubes without considering temperature effects.