Summer 2015 Thermodynamics Question Paper

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GUJARAT TECHNOLOGICAL UNIVERSITY
Diploma Engineering - SEMESTER–III • EXAMINATION – SUMMER • 2015
Subject Code: 3331902 Date: 06-05-2015
Subject Name: Thermodynamics
Time: 02:30 pm - 05:00 pm Total Marks: 70

Instructions:
1. Attempt all questions.
2. Make Suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
4. Use of programmable & Communication aids are strictly prohibited.
5. Use of only simple calculator is permitted in Mathematics.
6. English version is authentic.

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Q.1 Answer any seven out of ten. 14

1. Define pressure and its units in SI system.

2. Differentiate heat &work.

3. Differentiate thermodynamic cycle and mechanical cycle.

4. Explain closed system with sketch.

5. Write statement of zeroth law of thermodynamics.

6. Give examples of reversible process.

7. Define system and surroundings.

8. Write first law of thermodynamics for cyclic process.

9. Explain cut-off ratio.

10. Define thermal efficiency of heat engine.

Q.2 (a) A system contains 10Kg of a gas. During a process 15 KJ work is done on the system
& 40KJ heat rejected from the system. Find change of specific internal energy of the system. 03

OR

(a) If a system expands from 1m3 Volume to 4m3Volume at constant pressure. 10 bar.
Find boundary work during the process. 03

(b) Apply steady flow energy equation to nozzle. 03

OR

(b) Apply steady flow energy equation to boiler. 03

(c) With help of joule experiment explain first law of thermodynamics. 04

OR

(c) Prove that internal energy is a point function. 04

(d) Define (i) heat engine (ii) refrigerator (iii) heat pump (iv) entropy. 04

OR

(d) Represent Carnot cycle on P-V and T-S diagram and explain its processes. 04

Q.3 (a) Draw following process on P-V and T-S diagram.
(i) constant pressure process (ii) isothermal process. 03

OR

(a) Define (i) specific heat at constant pressure (CP) (ii)specific heat at constant volume(CV). 03

(b) Explain universal gas constant (Ru) & write is mathematical relation with characteristic gas constant(R)with example. 03

OR

(b) Explain Boyle’s law with neat sketch. 03

(c) Air of initial volume 0.1m3& pressure 1.5bar absolute pressure is expanded up to final
volume 0.6m3 Isothermally. Find (i) final absolute pressure (ii) heat transfer during process. 04

 OR

(c) 1 kg of gas enclosed in a closed vessel has absolute pressure 2 bar & temperature 30o C. If it is compressed up to 6 bar pressure find (i)final temperature & (ii)Change in internal energy.
Take CP =1.005 kJ/kgk & gas constant R=0.287 kJ/kgk. 04

(d) Derive characteristic equation for ideal gas. 04

OR

(d) Represent diesel cycle on P-V& T-S diagrams and explain its processes. 04

Q.4 (a) Differentiate power producing cycle and power absorbing cycle. 03

OR

(a) State limitations of first law of thermodynamics. 03

(b) Explain Kelvin Plank statement of second law of thermodynamics with neat sketch. 04

OR

(b) Gas turbine works on brayton cycle between 6bar &1bar pressure find air standard efficiency. Take γ=1.4 04

(c) Derive equation of air standard efficiency of an Otto cycle. 07

Q.5 (a) Explain thermodynamic equilibrium. 04

(b) Prove that CP - CV=R. 04

(c) Prove that (C.O.P)Heat pump = (C.O.P)Refrigerator + 1. 03

(d) Differentiate process and cycle. 03

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