14.11 Time to Completely Evaporate a Drop\ Consider convective mass transfer from tiny spherical droplets of water suspended in dry air as evaporation occurs at the droplet surface. The droplets being very small, gravitational force in relation to viscous drag is not as dominating and there are also small updrafts leading to no relative velocity between the droplets and the air. The droplet temperature remains constant at 40\\\\deg C. The diffusivity of water vapor in air at this temperature is 0.273 \\\\times 104 m2/s, and the density of water is 1000 kg/m3. Vapor pressure data can be found in Appendix C.10. 1) Equate the time rate of change of a droplet mass to the water loss through convective mass transfer at its surface so that you end up with a differential equation for radius, r. 2) Solve the equation in step 1 to find an expression for the time it takes for the droplet to shrink to a radius, r, starting from an initial radius, ri. 3) Calculate the time it takes for a 0.1 mm radius drop to completely evaporate.