Chemical Engineering problem. Mass Transfer.

Dry air flowing at 4 m/s (room temperature and pressure) is passed through a cylindrical tube of 2.5 cm diameter and 0.5 m length. The tube is made of naphthalene and is slowly sublimating over time. (Note that this could be an air humidification device if instead of naphthalene, the tube were porous with a thin water layer inside). Our goal is to calculate the naphthalene concentration in air at the end of the pipe. Calculate the convective mass transfer coefficient of this process and the flux at the entrance of the tube (i.e. when the driving force is maximum).

The molecular weight and density of naphthalene is 128 g/mol and 71.1 lb/ft³, respectively. The vapor pressure of naphthalene at this condition is 0.8 mmHg. Diffusion of naphthalene in air at 45 C is 6.92x10^-6 m²/s, density and viscosity of air are 1.1 kg/m³ and 1.92x10^-5 kg/(m s).

Look for the empirical Sherwood equation in the pdf file 007 Dimenssionless numbers.pdf Download 007 Dimenssionless numbers.pdf. Note that you have to define if the flow is turbulent or laminar, as defined in the PDF, to select the proper Sherwood relationship.