A small droplet of liquid detergent, falling through air in a spray drying tower, has its diameter reduced as water evaporates from the surface. If we assume that the temperature of the liquid within the drop remains at 290 K and the dry air is at 310 K, determine the moisture composition of the drying medium.
The following properties are available at the average temperature of the air, 300 K:
Kinematic viscosity of air = 1.5689 x 10^-5 m^2/s
Thermal diffusivity of air = 2.2156 x 10^-5 m^2/s
Mass diffusivity of water in air = 2.63 x 10^-5 m^2 /s
Density of air = 1.177 kg/m^3
Thermal conductivity of air = 2.624 x 10^2 J/m.s.K
Heat capacity of air = 1006 J/g.K
Surface temperature of drop, Ts = 290 K
Latent heat of vapourisation at Ts = 2461 J/g
Vapour pressure of water at Ts = 1.94 x 10^3 Pa