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ME 235 HW set 3
3.69
Is it reasonable to assume that at the given states the substance behaves as an ideal
gas?
Solution:
a) Oxygen, O
2
at
30°C, 3 MPa
Ideal Gas
( T » T
c
= 155 K from A.2)
b) Methane, CH
4
at
30°C, 3 MPa
Ideal Gas
( T » T
c
= 190 K from A.2)
c) Water, H
2
O
at
30°C, 3 MPa
NO
compressed liquid
P > P
sat
(B.1.1)
d) R134a
at
30°C, 3 MPa
NO
compressed liquid
P > P
sat
(B.5.1)
e) R134a
at
30°C, 100 kPa
Ideal Gas
P is low < P
sat
(B.5.1)
ln P
T
Vapor
Liq.
Cr.P.
a, b
c, d
e
3.74
Air in an internal combustion engine has 227
o
C, 1000 kPa with a volume of 0.1 m
3
.
Now combustion heats it to 1500 K in a constant volume process. What is the mass
of air and how high does the pressure become?
The mass comes from knowledge of state 1 and ideal gas law
m
=
P
1
V
1
RT
1
=
1000 kPa
×
0.1 m
3
0.287 kJ/kgK
×
(227 + 273) K
=
0.697 kg
The final pressure is found from the ideal gas law written for state 1 and state 2 and
then eliminate the mass, gas constant and volume (V
2
= V
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This note was uploaded on 03/18/2010 for the course IOE 201 taught by Professor Dennisblumenfield during the Fall '09 term at University of MichiganDearborn.
 Fall '09
 DennisBlumenfield

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