The final step of a manufacturing process in which a protective coating is applied to the inner surface of a circular tube involves passage of dry, atmosphere air through the tube to remove a residual liquid associated with the process. Consider a coated 5 − m -long tube with an inner diameter of 5 0 mm . The tube is maintained at a temperature of 300 K . and the residual liquid exists as a thin film whose corresponding vapor pressure is 15 mm Hg . The molecular weight and diffusion coefficient of the vapor are M A = 70 kg/kmoland D A B = 10 − 5 m 2 /s , respectively. Air enters the tube at a mean velocity of 0. 5 m is and a temperature of 3 00 K . (a) Estimate the partial pressure and mass density of vapor in the air exiting the lube. (b) What is the rate of liquid removal from the tube in kg/s?
The final step of a manufacturing process in which a protective coating is applied to the inner surface of a circular tube involves passage of dry, atmosphere air through the tube to remove a residual liquid associated with the process. Consider a coated 5 − m -long tube with an inner diameter of 5 0 mm . The tube is maintained at a temperature of 300 K . and the residual liquid exists as a thin film whose corresponding vapor pressure is 15 mm Hg . The molecular weight and diffusion coefficient of the vapor are M A = 70 kg/kmoland D A B = 10 − 5 m 2 /s , respectively. Air enters the tube at a mean velocity of 0. 5 m is and a temperature of 3 00 K . (a) Estimate the partial pressure and mass density of vapor in the air exiting the lube. (b) What is the rate of liquid removal from the tube in kg/s?
Solution Summary: The author explains the partial pressure and mass density of vapor in air at exit.
The final step of a manufacturing process in which a protective coating is applied to the inner surface of a circular tube involves passage of dry, atmosphere air through the tube to remove a residual liquid associated with the process. Consider a coated
5
−
m
-long tube with an inner diameter of
5
0
mm
. The tube is maintained at a temperature of
300 K
. and the residual liquid exists as a thin film whose corresponding vapor pressure is
15 mm Hg
. The molecular weight and diffusion coefficient of the vapor are
M
A
=
70
kg/kmoland
D
A
B
=
10
−
5
m
2
/s
, respectively. Air enters the tube at a mean velocity of
0.
5 m
is and a temperature of
3
00
K
.
(a) Estimate the partial pressure and mass density of vapor in the air exiting the lube.
(b) What is the rate of liquid removal from the tube in kg/s?
A polyethylene (PE) membrane is being used as an oxygen barrier. Oxygen is being supplied on the high pressure side at 0.25 kg/m3, and on the other side is a vacuum (concentration of oxygen is 0 kg/m3). If the desired flux is 4E-8 kg/m2s, what should the thickness of the PE membrane be? Answer in mm. The diffusion coefficient of oxygen in PE at the operating temperature is 4.5E-11 m2/s. Equation is J= -D(C1-C2/X1-X2)
Design a spherical tank, with a wall thickness of 2 cm that will assure that nomore than 50 kg of hydrogen will be lost per year. The tank, which will operateat 500 °C, can be made of nickel, aluminum, copper, or iron. The diffusioncoefficient of hydrogen and the cost per kg for each available material is listedhere. (Assume that the tank capacity is 15 kg)
Material D0 (cm2/s) Q (cal/mol) Cost ($/kg)Nickel 0.0055 8900 9.0Aluminium 0.16 10340 1.32Copper 0.011 9380 2.43Iron (BCC) 0.0012 3600 0.33
Estimate the interfacial heat transfer coefficient for evaporation of a thin film of
saturated liquid water at atmospheric pressure. The liquid film rests on a flat, solid
surface to which a constant and uniform heat flux of 150 kW/m? is applied. The
accommodation coefficient may be taken to be 0.05. If the liquid film thickness is 0.2
mm, compare the interfacial vaporization resistance with the conduction resistance
through the liquid film.
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