A common process for increasing the moisture content of air is to bubble it through a column of water. The air bubbles are assumed to be spheres having a radius of 1.0mm, and are in thermal equilibrum with the surrounding water at 298K. The vapor pressure of water is 0.03 atm at 298K, and the total pressure of the gas inside the air bubble is 1.0 atm.

a) Draw a picture of the physical system and list at least five reasonable assumptions for the mass transfer aspects of the water evaporation process. State what coordinate system should be used.

b)What are the simplified differential forms of Fick's flux equation for water vapor (species A) and the general differential equation for mass transfer in terms of concentration cA ?

c) Propose reasonable boundary and initial conditions