Air passes through a naphthalene tube, that has an inside diameter of 2.5 cm, flowing at a bulk velocity of 15 m/s. The air is at 283 K and an average pressure of 1:013 × 105 Pa.
Assuming that the change in pressure along the tube is negligible and that the naphthalene surface is at 283 K, determine the length of tube that is necessary to produce a naphthalene concentration in the exiting gas stream of 4:75 × 10-4 mol/m3.
At 283 K, naphthalene has a vapor pressure of 3 Pa and a diffusivity in air of 5:4 × 10-6 m2/s.