Experimental study on flow characteristics of liquid in circular microtubes

Glass, silicon, and stainless steel microtubes with diameters of 79.9-166.3 mum, 100.25-205.3 mum, and 128.76-179.8 mum, respectively, were employed to study the characteristics of frictional resistance for deionized water flow ill microtubes. Glass and silicon microtubes call be treated as smooth ones. whereas stainless steel microtubes with 3%-4% relative roughness has to be treated as coarse ones. It call be concluded from experimental results that for fully-developed water flow in smooth glass and silicon microtubes. the product of Darcy friction factor f and Reynolds number Re remains approximately 64, which is consistent with the results ill macrotubes. While the value of f . Re for water flog, ill rough stainless steel microtubes is 15%-37% higher than 64, it is distinctly different from the conventional conclusion that relative roughness below 5% has no effect oil the flow resistance for incompressible fluid flow ill macrotubes.