Air at 20oC, 40 % RH flows over a water surface at a velocity of 1.4 m/s; length parallel to flow is 200 mm. If average surface temperature is 16oC, calculate the amount of water evaporated per hour/m2 of the surface. Take: Partial pressure of water vapour at 20oC and 40 % RH, Pwa = 0.011 bar, The vapour pressure at 16oC and saturated, Pws = 0.017 bar Viscosity of air = 16.38 x 10-6 kg/ms Density of air = 1.22 kg/m3 , and Diffusion coefficient; D = 0.256 x 10-4 m2 /s