Several thin sheets of naphthalene, 0.25 cm thick and 10 cm square, are arranged parallel to each other with their centers at 1-cm intervals. Air at 273 K and 1:013 × 105 Pa enters this sandwich arrangement with a bulk velocity of 15 m/s. At 273 K, the mass diffusivity for naphthalene in air is 5:14 × 10-6 m2/s, the Schmidt number is 2.57, and the vapor pressure of naphthalene is 1.0 Pa. Determine the concentration of naphthalene in the air as it leaves the arrangement, evaluating the mass-transfer coefficient using the
(a) Reynolds analogy;
(b) von Ka´rma´n analogy;
(c) Chilton-Colburn analogy.
Determine the length of time the sheets must be exposed until half of their mass will be sublimed under these conditions.