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Spring 2006
1
ME 201
Thermodynamics
Homework #6 Solution
1. (10 pts) What is the enthalpy, internal energy, specific volume, and entropy for
steam at 1107
°
C and 27 MPa?
Solution:
Substance Type: Compressible (steam)
Problem Type: State
We are given steam at 27 MPa and 1107
°
C. First, we must determine the fluid phase.
We go to the saturation pressure table, A5, and find the boiling temperature at 27
MPa. However, we note that the table does not go up that far. This means we are
beyond the critical point and can treat the steam as superheated vapor.
So now we go to the superheat table, A6, and find that again we do not have a table
entry at either 27 MPa or 1107
°
C. This means we will have to set up a double
interpolation. To do so we set up the table shown below and enter the values from the
steam tables at 25 MPa, 30 MPa, and 1100
°
C, 1200
°
C.
P=25 MPa
P=27 MPa
P=30 MPa
T
v
u
h
s
v
u
h
s
v
u
h
s
1100
0.02517
4206.1
4835.4
7.5825
0.0235
4201.7
0.0210
4195.2
4823.9
7.4906
1107
1200
0.02716
4424.6
5103.5
7.7710
0.0226
4415.3
5094.2
7.6807
We begin our double interpolation by interpolating in pressure, so, for example, at
1100
°
C for specific volume we have
MPa
25

MPa
30
MPa
25

MPA
27
=
MPa)
v(25

MPa)
v(30
MPa)
v(25

MPa)
v(27
or solving for v(27 MPa)
/kg
m
0235
.
0
25
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 Spring '06
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