The Entrance Effect on Gases Flow Characteristics in Micro-tube  

作　　者：Chengwen Li Li Jia Tiantian Zhang 

机构地区：[1]Department of Power Engineering,School of Mechanical and Electronic Control Engineering,Beijing Jiaotong University,Beijing,100044,China

出　　处：《Journal of Thermal Science》2009年第4期353-357,共5页热科学学报(英文版)

基　　金：supported by the National Natural Science Foundation of China (No. 50776006);"863" plan (No. 2006AA05Z228);Technological Innova tion Fund of Excellent Doctoral Candidate of Beijing Jiaotong University (No. 48013)

摘　　要：Entrance region may have important effect on gases flow characteristics in micro-channels. It's concluded in the available papers that the entrance effect causes significant difference. An experimental system of single-phase gas flow characteristics in microchannels was set up. Flow characteristics of nitrogen in PEEK polymer micro-tube (hydraulic diameter is 553btm) was studied experimentally. According to the data of nitrogen flow in the micro-tube with the length ranging from 0. 1m to1.524m, it is shown that the friction constant becomes higher when the tube becomes shorter. By using pipe cutting methods, it's confirmed that entrance effect is one of the key factors that cause friction constant higher than conventional theory. It's found that friction constant of fully developed flow is lower than the value predicted by conventional theory in turbulent region. The result indicates that the flow transition occurs at Reynolds number ranging from 1600-2000. The phenomenon of obvious early transition is not found.

关 键 词：MICROCHANNEL the length of entrance region entrance effect constant friction method of cutting tube 

分 类 号：O357[理学—流体力学]