Dehumidifiers are used in a vast amount of applications, from residential to industrial humidity control. In addition, many chemical processes require a precise degree of humidity control. In one particular process, water vapour is quenched from the air on the surface of a solid sorbent material. (Water vapor is being transferred to the solids.) It is desired to estimate the mass-transfer coefficient _G in kg mol/s/m2/Pa for water vapor in air at 301.6 K and 101.32 kPa flowing in a large duct past solids of various geometries. The average velocity of gas in the duct is 3.66 m/s. The water vapor concentration in the bulk air is small, so the physical properties of air can be used. Estimate _g for the following geometries:

A) A single sphere having a diameter of 24.5 mm. (B) A packed bed (porosity = 0.35) of 24.5 mm-diameter spheres.