Experimental Analysis of The Effect of Hydrophobic Coating on Pressure Drop in Small Pipes

This article discusses the results of an experiment to quantify the effect of hydrophobic coating LT-8 on frictional drag within water flowing through pipes within the order of millimetres. Pipes in 1mm increments of between 1mm to 5mm diameter were tested. The 1mm, 2mm, and 5mm pipes demonstrated frictional drag reduction of 3.79%, 3.12%, and 4.28%, respectively. The 3mm and 4mm pipes showed an increase in frictional drag of 10.07% and 4.66%, respectively. The 2mm and 4mm pipes were also tested with in a half application of hydrophobic coating. The ½ coated 2mm pipe portrayed a 1.485% decrease in drag, which shows drag reduction is proportional to the quantity of coating applied. The ½ coated 4mm pipe showed a 1.79% increase in drag which again shows proportionality to the trend and its quantity of coating. The conclusions made from the evidence is that it may be possible that as Reynolds number increases, past those seen in the 1mm and 2mm pipes, the equilibrium state of the fluid-air interface becomes compromised. This then becomes a Wenzel wetting state and in turn increases drag. As the Reynolds number increases further, as in the 5mm pipe, drag reduction becomes evident.