KING ABDULAZIZ UNIVERSITY.
Faculty of Engineering, Rabigh Branch.
Mechanical Engineering Department.
Subject: Thermodynamics (I) MEP261.
Student Name:
Student Number:
Time: 2 hr. Group: ZA.
Final Exam.
Fall 1432/1433 H.
Number of Question
Mark
1a
1b
Property Tables are allowed.
2a 2b
3a
Total
Answer the following questions:
Question (1)
(8 Marks)
1a)Water is being heated in a closed pan on top of
a range while being stirred by a paddle wheel.
During the process, 30 kJ of heat is transferred to
the water, and 5 kJ of heat is lost to the
surrounding air. The paddle-wheel work amounts
to 500 N · m. Determine the final energy of the
system if its initial energy is 10 kJ. (2 Marks)
Sol.
Page 1 of 9
Examiner: Dr. Walid Aniss.
3b
4
30
Page 2 of 9
Examiner: Dr. Walid Aniss.
KING ABDULAZIZ UNIVERSITY.
Faculty of Engineering, Rabigh Branch.
Mechanical Engineering Department.
Subject: Thermodynamics (I) MEP261.
Final Exam.
1b) Complete these data for H2O:
Fall 1432/1433 H.
T, °C p, kPa
400
u, kJ/kg
v, m3/kg
Property Tables are allowed.
( 6 Marks)
Phase description
x
1450
220
190
Student Name:
Student Number:
Time: 2 hr. Group: ZA.
Saturated vapor
2500
4000
3040
Sol.
Solution
Question (2)
( 7 Marks)
2.a) A frictionless piston–cylinder device contains 2 kg of
nitrogen at 100 kPa and 300 K. Nitrogen is now compressed
slowly according to the relation Pv1.4 = constant until it reaches
a final temperature of 360 K. Calculate the work
input during this process.
(3 Marks)
Page 3 of 9
Examiner: Dr. Walid Aniss.
Solution
2.b) Refrigerant-134a enters a 28-cm diameter pipe steadily at
200 kPa and 20°C with a velocity of 5 m/s. The refrigerant gains
heat as it flows and leaves the pipe at 180 kPa and 40°C.
Determine (a) the volume flow rate of the refrigerant at the
inlet, (b) the mass flow rate of the refrigerant, and (c) the
velocity and volume flow rate at the exit. (4 Marks)
Solution
Page 4 of 9
Examiner: Dr. Walid Aniss.
KING ABDULAZIZ UNIVERSITY.
Faculty of Engineering, Rabigh Branch.
Mechanical Engineering Department.
Subject: Thermodynamics (I) MEP261.
Fall 1432/1433 H.
Final Exam.
Student Name:
Student Number:
Time: 2 hr. Group: ZA.
Property Tables are allowed.
Question (3)
( 9 Mark)
3.a) An air conditioner removes heat steadily from a house at a
rate of 750 kJ/min while drawing electric power at a rate of 6
kW. Determine (a) the COP of this air conditioner and (b) the
rate of heat transfer to the outside air.
( 3 Marks)
Answers: (a) 2.08, (b) 1110 kJ/min
Solution
.
Page 5 of 9
Examiner: Dr. Walid Aniss.
3.b) A piston–cylinder device contains 5 kg of steam at 100°C with a
quality of 50 percent. This steam undergoes two processes as follows:
1-2 Heat is transferred to the steam in a reversible manner while the
temperature is held constant until the steam exists as a saturated vapor.
2-3 The steam expands in an adiabatic, reversible process until the
pressure is 15 kPa.
(a) Sketch these processes with respect to the saturation lines on a single
T-s diagram.
(b) Determine the heat added to the steam in process 1-2, in kJ.
(c) Determine the work done by the steam in process 2-3, in kJ. (6 Marks)
Sol.
Solution
Page 6 of 9
Examiner: Dr. Walid Aniss.
Page 7 of 9
Examiner: Dr. Walid Aniss.
KING ABDULAZIZ UNIVERSITY.
Faculty of Engineering, Rabigh Branch.
Mechanical Engineering Department.
Subject: Thermodynamics (I) MEP261.
Fall 1432/1433 H.
Final Exam.
Question (4)
Student Name:
Student Number:
Time: 2 hr. Group: ZA.
Property Tables are allowed.
(6 Marks)
Air enters the compressor of a gas-turbine engine at 300 K and 100 kPa,
where it is compressed to 700 kPa and 580 K. Heat is transferred to air in
the amount of 950 kJ/kg before it enters the turbine. For a turbine
efficiency of 86 percent, determine (a) the fraction of the turbine work
output used to drive the compressor and (b) the thermal efficiency.
Assume variable specific heats for air.
.
Sol.
Page 8 of 9
Examiner: Dr. Walid Aniss.
Solution
Page 9 of 9
Examiner: Dr. Walid Aniss.