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Problem 3.1 [Difficulty: 2]
Given: Data on nitrogen tank
Find: Pressure of nitrogen; minimum required wall thickness
Assumption: Ideal gas behavior
Solution:
Ideal gas equation of state: p V M R T=
where, from Table A.6, for nitrogen R 55.16
ft lbf
lbm R
=
Then the pressure of nitrogen is p
M R T
V
= M R T
6
 D
3







=
p 140 lbm 55.16
ft lbf
lbm R
 77 460+( ) R
6
 2.5 ft( )
3

。
「
」
、
・
ヲ

ft
12 in






2
=
p 3520
lbf
in
2
=
cDt
pD2
/4
To determine wall thickness, consider a free body diagram for one hemisphere:
裡F 0= p
 D
2

4
 c  D t=
where c is the circumferential stress in the container
Then t
p  D
2

4  D c
=
p D
4 c
=
t 3520
lbf
in
2

2.5 ft
4

in
2
30 10
3
 lbf
=
t 0.0733 ft= t 0.880 in=

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Problem 3.1

  • 1. Problem 3.1 [Difficulty: 2] Given: Data on nitrogen tank Find: Pressure of nitrogen; minimum required wall thickness Assumption: Ideal gas behavior Solution: Ideal gas equation of state: p V M R T= where, from Table A.6, for nitrogen R 55.16 ft lbf lbm R = Then the pressure of nitrogen is p M R T V = M R T 6 D 3 = p 140 lbm 55.16 ft lbf lbm R 77 460+( ) R 6 2.5 ft( ) 3 。 「 」 、 ・ ヲ ft 12 in 2 = p 3520 lbf in 2 = cDt pD2 /4 To determine wall thickness, consider a free body diagram for one hemisphere: 裡F 0= p D 2 4 c D t= where c is the circumferential stress in the container Then t p D 2 4 D c = p D 4 c = t 3520 lbf in 2 2.5 ft 4 in 2 30 10 3 lbf = t 0.0733 ft= t 0.880 in=