EXPERIMENTAL STUDY ON FLOW CHARACTERISTICS OF LIQUID IN CIRCULAR MICROTUBES

Glass, silicon and stainless steel microtubes with diameters of 79.9~166.3 µ m , 100.25~205.3 µ m and 128.76~179.8 µ m respectively were employed to study the characteristics of frictional resistance for deionized water flow in microtubes. Glass and silicon microtubes can be treated as smooth ones, while stainless steel microtubes with 3~4% relative roughness has to be treated as coarse ones. It can be concluded from experimental results that for fully-developed water flow in smooth glass and silicon microtubes, the product of Darcy friction factor ƒ and Reynolds number Re remains approximately 64, which is in consistence with the results in macro tubes. While the value of ƒ · Re for water flow in rough stainless steel microtubes is 15~37% higher than 64, which is distinctly different from the conventional conclusion that relative roughness below 5% has no effect on the flow resistance for incompressible fluid flow in macro tubes.