The Analysis of Flow Field in Microchannels

• Main Authors: Sheu, Jihn-Deng, 許進登
• Other Authors: Ching-Shung Chen
• Format: Others
• Language: zh-TW
• Published: 1997
• Online Access: http://ndltd.ncl.edu.tw/handle/02432046511697637489

碩士 === 淡江大學 === 機械工程學系 === 85 === The present work is concerned with the numerical investigation of gas flow in micro-channels with Knudsen numbers ranging from 0.02 to 0.16. The proposed model treats the flow as a continuum but assumes a slip condition on the channel wall. The results of the present study reveal some interesting features of micro- channel flows. First, due to the extraordinarily small dimensions, a large pressure is required to drive the flow. Although the pressure gradient is large, the velocity remains very small due to the high shear stress on the wall, in the cases studied, the maximum u velocity is only 1.16 m/sec for a pressure ratio of 2.701. Second, since the velocity is small, the corresponding Reynolds number is also relatively small, (0.012 - 0.089), for the flows simulated, they can be safely assumed to be laminar. Third, the calculated pressure distributions of nitrogen flows agree quite well with test data, the Knudsen numbers of these flows, Kn = 0.055 at the channel outlet which is the largest value in a channel, indicating they are in the slip flow region. The calculated pressure distribution of helium flow does not match test data, the corresponding outlet Knudsen number is 0.160, indicating it is in the transition flow region. Although more investigation is needed before definite conclusions can be drawn, the results of this study indicate that the slip model is able to predict micro-channel flows in the slip flow region, but further study is needed for flows in the transition flow region.