A very thin polymeric coating of thickness 0.1 mm uniformly coats a rectangular surface. The rectangular surface has a length of 20 cm and a width of 10 cm. the coating contains a solvent that must be evaporated away from the coating in order to cure the coating. Initially, there is 0.001 mole of solvent per cm3 of coating loaded in the coating.
A heated plate just beneath the surface maintains the coating at a uniform temperature of 40°C, and the vapor pressure exerted by the solvent is 0.05 atm at 40°C. Air gently flows parallel to the surface at a velocity of 5.0 cm/s. The surrounding air at 1.0 atm total system pressure and 20°C represents an ''infinite sink'' for mass transfer. You may neglect any molecular diffusion of the solvent through the very thin polymeric film and focus only on the convection aspects of the problem. The diffusion coefficient of species in air at 20°C is 0:1 cm2/s.
a. Determine the Reynolds, Schmidt, and Sherwood numbers associated with this process.
b. What is the film mass-transfer coefficient, ky, (mole fraction based driving force) associated with this process?
c. How long will it take for the solvent to completely evaporate from the coating?