Influence of Chemically Etched Roughness on Frictional Resistance of Micro-tubes

Chemical etching is a convenient process for enhancing three-dimensional (3D) roughness of internal surface of micro-tubes. The aim of this research work is to compare the frictional resistance and contact angle in smooth and rough stainless steel micro-tubes. At various inputs of Reynolds number in laminar regime (201.43 < Re < 1929.96), differential pressure has been measured for etched and unetched tubes with deionized water. In order to substantiate the effect of roughness on tube, contact angle is measured before and after etching to calculate roughness parameter. It is found that etching enlarges the inner diameter of the tube; hence new diameter should be considered for Poiseuille number (fRe) calculations. The role of etching on fRe is more significant on tube of inner diameter (ID) 0.932 mm, as compared to tube of ID 1.293 mm. Etching increases the contact angle of hydrophobic surface. This work would be applicable in design improvement of complex micro-devices when relative roughness plays a major role due to small scale.