MEAM 203
FALL 2002
THERMO  MIDTERM
I
Closed books.
Write clearly!
Explain all steps!
GOOD LUCK.
(50%)
1
.
An ideal gas undergoes a cycle consisting of the following three processes:
(i)
Process 12: Isothermal compression from pressure p
1
=100kPa, temperature
T1=300K, and the volume changes from volume V
1
=1.6m
3
to volume V
2
=0.2m
3
.
(ii)
Process 23:
Constant pressure expansion from volume V
2
back to volume V
1
.
(iii)
Process 31:
Constant volume process in which the gas pressure drops from p
3
to p
1
.
The gas’ specific heat at constant volume Cv=0.7 kJ/kgK and R=0.287 kJ/kgK.
(i)
(10%) Depict all three processes on T vs V and p vs V diagrams.
Mark along the
curves the properties that are maintained fixed in each process.
(ii)
(10%) Determine the work and heat interactions during process 12.
(iii)
(
5%) Determine the change of entropy during process 12.
(iv)
(10%) Determine the work and heat interactions during process 23.
(v)
(10%) Determine the change of entropy during process 23.
(vi)
(
5%) Determine the change of entropy during process 31.
(30%)
2
.
One kilogram of superheated water at 500C and one kilogram of saturated vapor, both
at 200kPa, are mixed in an adiabatic, constant pressure process.
Determine:
(i)
(10%) The final temperature.
(ii)
(10%) The entropy generation during this process.
(iii)
(10%) The work interaction.
Saturated Steam Table
P
(kPa)
T
(C)
v
v
(m3/kg)
u
v
(kJ/kg)
h
v
(kJ/kg)
s
v
(kJ/kgK)
200
120
0.886
2530
2707
7.13
Superheated Steam Table (p=200kPa)
T(C)
v
v
(m3/kg)
u
v
(kJ/kg)
h
v
(kJ/kg)
s
v
(kJ/kgK)
300
1.32
2809
3097
7.90
400
1.55
2967
3277
8.22
500
1.78
3130
3487
8.51
(20%) 3.
A Carnot heat engine consumes 1000J of heat from a hot reservoir at 1000K and
discharges heat to a cold reservoir.
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 Spring '08
 Bau
 Thermodynamics

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