The Arnold diffusion cell

2 For problem 3.1, assume an ideal gas and express the steady-state equation in terms of partial pressures. 

3 We wish to estimate the time it takes to evaporate a puddle of water. The depth of the puddle is 0.08 inches and covers a surface area of 2 ft2. Both the surr.ounding air (which is stagnant) and the water are at a constant temperature of 77°F. The absolute humidity is 0.001 lb water/lb dry air. Assume the evaporation to occur, through stagnant gas film that is 0.28 inches thick. The gas diffusion coefficient of water vapor at these conditions is 0.259 cm2/sec. 

4 For the system described in problem 3.3 develop a general expression for computing the water vapor concentration profile through the stagnant air film. 

5 A 30-ft-deep water well has a cross-sectional area of 5 ft2. The temperature of the water and the air in the well is 84°F. If there is a slight breeze of air with humidity of 0.03 lbm H20/lbm dry air blowing across the top of the well, estimate the rate at which the water evaporates. 

6 A 10-ft-diameter cylindrical tank contains water at a level of 3 ft below, the top of the vessel. The capacity of the tank is 80 gallons. If the top of the tank is open, determine the weight of water evaporated per unit time. Assume dry air at 90°F is blowing across the vessel s top. 

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