Calculate in how much time (s) the water layer evaporates if the layer is 0.4 mm thick.

Physical transport phenomena: mass transfer

Water layer on concrete

On a smooth floor in a factory lies a layer of water covering a rectangular area of 4 m length by 3 m width. Air is blown over the surface in a longitudinal direction, at a velocity of 50 km/h, so the water evaporates.

The air is dry, at 1 atm and at 30°C. The diffusion coefficient of water vapor in air in this situation is 2.6×10-5 m2/s.

Calculate the convective mass transfer coefficient of water evaporating into air (m/s)). Look up the required formula to calculate Sherwood number for this situation. Also look up the necessary data of air to be able to calculate the relevant dimensionless numbers. Mention the sources where you found the data.

Calculate in how much time (s) the water layer evaporates if the layer is 0.4 mm thick. You will need to look up the saturation density of water vapour at 30 oC and 1 atm. Mention the source where you found the data.