Experimental study of local mass transfer from a flat plate in uniform flow using electronic speckle pattern interferometry

In this paper an investigative study of the relationship between mass and momentum transport, which have a mutual dependence, is presented. Mass transfer is an important design consideration in engineering processes such as evaporation, chemical reactions, corrosion and mixing. The effect that Reynolds number and distance from the leading edge has on mass transport from fluid to fluid interface on flat plate geometry is examined. A concentration profile is developed above a surface by passing airflow across the plate containing a well of ethanol. The rate of mass transfer is obtained from the concentration profile produced as the ethanol vapour diffuses in the airflow. Measurements are taken using the non-intrusive optical technique of Electronic Speckle Pattern Interferometry (ESPI), which has not been applied in this manner before. This novel approach offers the ability to measure in real time the mass transfer rate. A phase-shifting algorithm is also employed to give whole field measurements. The experimental results compare well to the theoretical prediction, showing that as expected the Sherwood number increases with increasing Reynolds number.