Experimental Investigation of Gaseous Flow in a Micro-Tube

Experimental investigations on nitrogen gas flow characteristics were performed for a micro-tube. The micro-tube was fabricated in a stainless steel block by electrical discharge machining (EDM). The tube diameter was 326 μm and the ratio of length to diameter was 200. The stagnation pressure was chosen in such a way that the exit Mach number ranged from 0.1 to 1.4. The outlet pressure was fixed at atmospheric conditions. The pressure was locally measured at five locations along tube length to determine local values of Mach number and friction factor for a wide range of flow regime from laminar to turbulent flow. The result shows that f·Re is a function of Mach number and higher than incompressible value, 64 due to the compressibility effect. The values of f·Re were compared with f·Re correlation in literature. In additional experiments, Mach number at the micro-tube exit was measured by using a Shadowgraph system which visualizes the shock wave of the gas. The micro-tube with 400 μm in diameter was used for the experiment. The super sonic flow was observed since Mach number at the micro-tube exit was beyond unity. The experimental results for laminar flow were compared with the numerical results obtained by the arbitrary-Lagrangian-Eulerian method. The both results are in excellent agreement.