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B.E. (Mechanical Engineering / Power Engineering) Fourth Semester (C.B.S.)
Engineering Thermodynamics
P. Pages : 3 NJR/KS/18/4424/4448
Time : Three Hours *0773* Max. Marks : 80
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Notes : 1. All questions carry marks as indicated.
2. Solve Question 1 OR Questions No. 2.
3. Solve Question 3 OR Questions No. 4.
4. Solve Question 5 OR Questions No. 6.
5. Solve Question 7 OR Questions No. 8.
6. Solve Question 9 OR Questions No. 10.
7. Solve Question 11 OR Questions No. 12.
8. Due credit will be given to neatness and adequate dimensions.
9. Assume suitable data whenever necessary.
10. Diagrams and chemical equations should be given whenever necessary.
11. Illustrate your answers whenever necessary with the help of neat sketches.
12. Use of non programmable calculator is permitted.
13. Use of steam table & Mollier Chart is permitted.
14. Solutions should be provided with appropriate P-V and T-S diagram.

1. a) Explain thermodynamic system and its types with suitable examples. 6

b) A gas in a piston cylinder arrangement undergoes an expansion process for which the 7
n
relation between pressure and volume is given by p  constant . The initial pressure is
3 bar and initial volume is 0.1m3 and the final volume is 0.2 m3 . Determine the work for
the process is kJ if (i) n = 1.5 (ii) n = 1.0 and (iii) n = 0.

OR

2. a) Explain the terms : 6

i) Specific heat at Constant Volume.

ii) Specific heat at Constant Pressure.

Prove that Cp  Cv  R .

b) 0.1m3 of an ideal gas at 300 K and 1 bar is compressed adiabatically to 8 bar. It is then 7
cooled at constant volume and further expanded isothermally so as to reach the initial
conditions. Calculate the net work done and net heat transfer during the cycle.
kJ kJ
Assume Cp  1.005 , Cv  0.7178
kgk kgk

3. a) Prove that in a constant volume process the change in internal energy is equal to the heat 4
transfer during that process.

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 b) An Ideal Gas of 20.6 bar, 0.142m3 and 337ºC expands according to the law p  C to six 10
times the initial volume. The gas is further cooled to 30ºC according to the law   C .
Finally compressed back to initial condition according to the law pk  C . Find the net
work done and net heat transfer during the cycle. Show the cycle on p and T - S diagrams.

OR

4. a) State the general steady flow energy equation and obtain its simplified form for (i) steam 5
nozzle (ii) Boiler.

b) Steam with enthalpy 3000 kJ/kg and specific volume 0.187 m3 / kg enters the steam nozzle 9

and learn with 2762 kJ/kg of enthalpy and 0.498m3 / kg of specific volume. The inlet
velocity of steam is 60 m/s and the inlet area is 0.1m2 . Find the velocity of steam at the
exit of the nozzle, mass flow Rate and exit Area.

5. a) State and explain the second law of thermodynamics. 5

b) Prove that the COP of pump is greater than the COP of Refrigerator by unity. 3

c) An engineer claims to have developed a refrigerator that removes heat from a cold space at 5
5º C and transfers it to the surrounding air at 30ºC, while maintaining its COP of 7.5. Is
this claim reasonable? Why?
OR
6. a) State and prove Clausius theorem. 6

b) One kg of Ice at 5º C is exposed to the atmosphere at 22ºC. The ice melts and comes into 7
thermal equilibrium with the atmosphere. Determine the entropy increase of the universe.
Cp of Ice  2.09kJ / kg k
Latent heat of fusion of Ice  0.333MJ / kg .

7. a) Explain the following terms. 5

i) Wet steam
ii) Latent heat of Vaporisation
iii) Enthalpy of steam
iv) Superheated steam
v) Dryness fraction

b) One kg of steam at pressure of 17 Bar and dryness fraction 0.95 is heated at constant 8
pressure until it is completely dry. Determine :
i) Increase in volume.
ii) Quantity of heat supplied.
iii) Change in entropy.
OR

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8. a) Explain the method to determine the dryness fraction of steam using combined separating 6
and throttling calorimeter.

b) Steam enters an engine at a pressure of 10 Bar and 400ºC. It is exhausted at 0.2 Bar and 7
0.9 Dry. Find :
i) Drop in enthalpy
ii) Change in entropy

9. a) Why Carnot cycle is not used in actual power plant. 3

b) In a Rankine cycle the steam at inlet to the turbine is dry saturated at a pressure of 30 Bar 10
and exhaust pressure is 0.2 Bar. Determine :
i) Pump work.
ii) Turbine work.
iii) Rankine Efficiency.
iv) Heat Rejected in Condenser.
v) Dryness fraction at turbine exit.

OR

10. a) What are the methods which can lead to the increase in thermal efficiency of Rankine 5
Cycle.

b) A steam power plant uses the following cycle. Regeneration with inlet condition of 40 Bar 8
and 400ºC. Steam is bled at 10 Bar in Regenerative heating. The exit pressure is 0.8 Bar.
Neglecting pump work determine the efficiency of the cycle.

11. a) Derive an Expression for the thermal efficiency of Diesel Cycle. 7

b) In an Otto cycle the Compression Ratio is 7 and the compression begins at 1 Bar and 7
35ºC. The maximum temperature of the cycle is 1100ºC. Find :
i) Temperature and pressure at all the points of the cycle.
ii) Work done per kg of air.
iii) Cycle Efficiency.

OR

12. An air Standard Dual Cycle has Compression Ratio of 16 and the compression begins at 1 14
Bar and 50ºC. The maximum pressure is 70 Bar. The heat transferred to air at constant
pressure is equal to that at constant volume. Draw the cycle on p and T - S diagrams.
Determine :
i) Total heat supplied.
ii) Work Done
iii) Thermal Efficiency
iv) Mean Effective Pressure.

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