2.13b. Dissolution of a solid sphere into a flowing liquid stream.
Estimate the mass-transfer coefficient for the dissolution of sodium chloride from a cast sphere, 1.5 cm in diameter, if placed in a flowing water stream. The velocity of the 291 K water stream is 1.0 m/s.
Assume that the kinematic viscosity at the average liquid film conditions is 1.02 ´ 10Ð6 m2/s, and the mass diffusivity is 1.25 ´ 10Ð9 m2/s. The solubility of NaCl in water at 291 K is 0.35 g/cm3, and the density of the saturated solution is 1.22 g/cm3 (Perry and Chilton, 1973) .

Solution
From Prob. 2.10:
2.14b. Sublimation of a solid sphere into a gas stream.
During the experiment described in Problem 2.2, the air velocity was measured at 10 m/s. Estimate the mass-transfer coefficient predicted by equation (2-36) and compare it to the value measured experimentally. The following data for naphthalene might be needed: Tb = 491.1 K, Vc = 413 cm3/mol.

Solution
For air at 347 K and 1 atm:
Estimate DAB from the Wilke-Lee equation
Lennard-Jones parameters for naphthalene
2.15b. Dissolution of a solid sphere into a flowing liquid stream.
The crystal of Problem 1.26 is a sphere 2-cm in diameter. It is falling at terminal velocity under the influence of gravity into a big tank of water at 288 K. The density of the crystal is 1,464 kg/m3 (Perry and Chilton, 1973).
a) Estimate the crystal's terminal velocity.

Solution
b) Estimate the rate at which the crystal dissolves and compare it to the answer obtained in Problem 1.26.

Solution
From Prob.1.26
From Prob.1.26: