Name ____________________________
F
IRST
H
OUR
E
XAMINATION

TAM 324/CEE300
Friday February 16, 2007
• Work all problems in spaces provided
• One page of handwritten notes permitted.
1.
(10 points)
Nitrogen gas can be used to improve the properties of steel. A sheet of steel
1.5 mm thick has Nitrogen atmospheres on both sides at 1200
o
C and is permitted to
achieve a steadystate diffusion condition
The diffusion coefficient for Nitrogen in steel
at this temperature is 6x10
11
m
2
/s, and the diffusion flux is found to be 1.2x10
7
kg/m
2
s.
Also, it is known that the concentration of Nitrogen at the in the steel at the highpressure
surface is 4 kg/m
3
.
(a)
(3pts)
Write out
the appropriate governing equation that describes
this diffusion process.
(b)
(7pts)
Compute
the distance into the sheet from this high
pressure side that the concentration will be 2.0 kg/m
3
.
B
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