thnx

A 15cm by 15cm square silicon wafer is covered by a thin coating of a photoresist polymer dissolved in the volatile solvent methyl ethyl ketone (MEK). The wet coating contains 40wt% polymer solid and 60wt% solvent, and the total mass loading of the coating is 2.8g. The solvent can be considered to be in a liquid state. The solvent will be evaporated from the polymer surface by flowing air parallel to the surface of the wafer, as shown in the following Figure. The solvent vapor must transfer from the coating surface through the hydrodynamic boundary layer (dotted line in the following Figure) formed by the air flow over the surface. During the solvent evaporation process, a heating plate beneath the wafer maintains the coating at a uniform temperature of 27C, and the vapor pressure exerted by the solvent at this temperature is constant at 99.4mm Hg. The molecular weight of MEK is 72g/mol and density of MEK is 805kg/m. The flowing air is also at 27C and 1.0atm total system pressure. The rate of solvent evaporation is limited by the convective mass-transfer process. The diffusion coefficient of MEK in air is 0.08cm/s at 27C and 1.0atm, the kinematic viscosity of air is 1.6 x 10 m/s. The flowing air has a bulk velocity of 3.2m/s. The flow of air is high enough that relative to the rate of solvent transfer, the concentration of solvent vapor in the bulk gas (CA) is very small and can be assumed to be near zero. Furthermore, any resistances associated with the molecular diffusion of the solvent through the very thin polymer coating can be neglected. Determine: a) the Schmidt number and the average Sherwood number for MEK evaporation process; b) flux of MEK from coating to the air; c) how long does it take for the solvent in the coating to be completely evaporated