Question

Liquid (A) flows down as a thin film over the outside surface of a vertical flat plate 1.5 m wide (W = 1.5 m) and 3.5 m long (L = 3.5). Inert gas (B) flows across (perpendicular to) the width of the flat plate at a speed of 5 m/s. The supply of (A) is 0.27 mol/s at one end of the plate and the flow is considered to be turbulent. The gas composition of (A) at the edge of the film is 14% and in the bulk 0%.

(B) can be assumed non-diffusing (NB = 0). The system is not dilute.

Viscosity of liquid (A), μA = 0.0000161 Pa×s = 1.61x10-5 Pa×s Diffusion coefficient of A through B, DAB = 1x10-5 m2/s Density of A, rA = 1.2 kg/m3
Total concentration, c = 44 mol/m3

How many meters of the plate will be dry from (A)? ‘show your working out’

Answer 1