Humid air at 20 ◦C and a relative humidity ϕ = 0.5 flows over a lake which is also at 20 ◦C. The lake is 200 m · 50 m big and the air flows over the longitudinal area with a velocity of 2 m/s. How...

Humid air at 20 ◦C and a relative humidity ϕ = 0.5 flows over a lake which is also at 20 ◦C. The lake is 200 m · 50 m big and the air flows over the longitudinal area with a velocity of 2 m/s. How much water evaporates per hour?

Given are the viscosity of air ν(20 ◦C) = 1.535 · 10⁻⁵
m²/s, the Schmidt number for water vapour-air Sc = ν/D = 0.6, the saturation pressure of water pWS(20 ◦C) = 2.337 · 10⁻³
MPa and the saturation density (20 ◦C) = 0.01729 kg/m³
.