A flat steel plate is 2.0 m in length and 2.0 m width and initially contains a very thin coating of lubricating oil used in a manufacturing process. An engineer is considering the feasibility of using hot forced air convection to remove the lubricating oil from the surface as an alternative to using harmful solvents to rinse the lubricating oil off the surface. In the present process, air at 386 K and 1.0 atm is blown parallel to the surface at a velocity of 50 m's. At this velocity, the location on the plate where the laminar flow ends is 0.097 m from the leading edge. The initial thickness of the liquid lubricating oil coating the surface is 10.0 m (1 * 10m). AT 386 K, the viscosity of air is 2.23 +10 kg/m.s, and the mass density of air is 0.917 kg/m'. At 386 K, the lubricating oil is slightly volatile with a vapor pressure of 0.20 Pa, and the liquid density of the lubricating oil is 1900 kg/m". At 386 K and 1.0 atm, the molecular diffusion coefficient of the lubricating oil vapor in the air, Das, is 0.040 cm.
(a) What is the Schmidt number for the mass transfer of lubricating oil vapor in air?