A flat steel plate is sprayed with 1.0 mm thick film of paint. The steel plate is 2.5 m by 1 m. The paint consists of benzene as the solvent. Fifty cubic meters per minute of air are blown into the drying chamber as shown in the Figure below. The chamber is 2.5 m in length, 2.5 m in height, and 1 m in width. The temperature of the air and the plate is 27 C and the system is maintained at a pressure of 1 atm. The paint surface exerts a partial pressure of 0.137atm. Under these conditions, the DAB equals 0.0972 cm2 s-1 and the viscosity of the benzene vapor is 1.569*10-5 m2 s-1.

As the air flows over the plate, a laminar boundary layer formed. The average mass transfer coefficient was determined to be: kc=0.664LDABReL1/2Sc1/3. Here, Re is the Reynolds number (Re=vvL) associated with flow of air over the plate. v is the free stream velocity, L is the characteristic length, and v is the viscosity of fluid. Sc is the Schmidt number (Sc=DABv). a) Determine the average mass-transfer convective coefficient. b) Assuming that the concentration of benzene vapor in the air stream is negligible, what would be the evaporation rate of benzene from the plate's surface. c) The concentration boundary layer can be related to the hydrodynamic boundary layer by c=Sc1/3, where and c are the hydrodynamic and the concentration boundary layers, respectively. We can assume that depends on Rex as =vvx5x=Rex5xx is the distance along the steel plate. Plot the concentration boundary layer thickness across the steel plate