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Chemical Engineering 150B Fall 2005
Problem Set #4
Due Wednesday September 28
th
, 2005
Note: There are
5
problems in this assignment (see back).
Problem 1.
(15 points) Consider liquid A evaporating into initially pure and incondensable
gaseous B, which has no solubility in liquid A, in a closed adiabatic and isothermal vessel shown
below:
This vessel initially has 0.4 liter of A with 75 cm
2
of surface area in a total volume of 20 liters.
After 4 minutes, the gas phase contains five percent A. Both A and B are ideal in the gas phase.
(a)
Calculate the mass transfer coefficient of A based on the initial flux of A? Note that the
vessel is isothermal at 298 K, and the equilibrium vapor pressure of A at 298K is 24 torr.
(b)
Calculate how much time it will take to reach ninety percent saturation of A in B?
Assume that the mass transport coefficient in (a) remains constant for all compositions
and pressures for this part.
Problem 2.
(15 points) A 1m square, thin plate of napththalene is oriented parallel to an air
stream flowing at 30 m/s.
The air is at 310 K and 1 atm.
The plate is at 300 K.
Determine the
rate of sublimation from the top of the plate assuming a pseudo steadystate situation.
[The following properties for naphthalene are known: Diffusivity of naphthalene is at 298 K =
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 Spring '08
 Bell
 Fluid Dynamics, Aerodynamics, Vapor pressure, Naphthalene, turbulent boundary layer

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