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DIPLOMA ENGINEERING – SEMESTER – 3 • EXAMINATION – WINTER - 2016
Subject Code: 3331902 Date: 22-11-2016
Subject Name: Thermodynamics
Time: 10:30 am to 01:00 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. State concept of air standard cycle.
2. List four types of system.
3. Define enthalpy and entropy.
4. Write four conditions for steady flow.
5. Represent isothermal process on P-V and T-S diagram.
6. Define heat engine and refrigerator.
7. Define ideal gas and throttling process.
8. State two applications of Carnot cycle.
9. Write equation of COP for reversed brayton cycle
10. Define process and cycle.
Q.2 (a) Classify system boundaries and give two examples of each type. 03
OR
(a) Differentiate point function and path function. 03
(b) Derive expression for work done during isentropic process. 03
OR
(b) Explain characteristics of gas constant (R). 03
(c) State and explain limitations of first law of thermodynamics. 04
OR
(c) Write full form of SFEE and apply SFEE Equation for steam engine. 04
(d) 10 kg air enters into a nozzle with negligible velocity. Its pressure reduces from 392.4
kPa to 196.4 kPa during the flow from the nozzle and temperature reduces from 9500C
to 7600C during the flow. Find velocity of air at exit. Take γ = 1.395, Cp = 1.005 KJ/Kg,
Cv= 0.72 KJ/Kg, and R = 0.285 kj/kgK. 04
OR
(d) Air has initial volume 0.6 m3, pressure 60 N/cm2 and temperature 900C. It is expanded isothermally up to pressure 15 N/cm2. Find work done and change in internal energy and
mass. Take R= 0.287 KJ/Kg K. 04
Q.3 (a) Explain specific heat at constant pressure (Cp). 03
OR
(a) One kg of gas enclosed in a closed vessel has absolute pressure 2 bar and temperature
270C. If it is compressed up to 5 bar pressure, find 1] final temperature 2] change in
internal energy. Take Cp = 1.005 KJ/Kg K and R = 0.297 KJ/KgK. 03
(b) Derive Cp – Cv = R with usual notations. 03
OR
(b) Derive equation of work done in polytropic process. 03
© In one otto cycle engine clearance volume is 30% of its swept volume. Find
air standard cycle efficiency if γ = 1.4. 04
OR
(c) Draw the dual cycle on P–V and T-S diagram and write the equation of air
standard efficiency of dual cycle. 04
(d) Classify thermodynamics cycles. 04
OR
(d) Draw the diesel cycle on P–V and T-S diagram and explain its processes. 04
Q.4 (a) A closed system executes adiabatic process due to which a change in internal energy
takes place. A work of 10 kJ is done by the system on surroundings during this process.
Determine change of specific internal energy of the system if system contains mass of 0.2 kg. 03
OR
(a) What is entropy and explain its importance in thermodynamics. 03
(b) A refrigerator keeps vegetables at temperature 100C by removing 50 kJ heat
from it. If it rejects 75 kJ heat into the atmosphere find its C.O.P. and work required. 04
OR
(b) A heat engine takes 10000 kJ/hr heat energy from source of temperature 3270C and rejects
5000 kJ/hr heat into sink of 270C temperature. Find out its thermal efficiency and decide
whether this heat engine is reversible one or irreversible one. 04
(c) Derive equation for air standard efficiency of otto cycle. 07
Q.5 (a) One gas turbine works on Brayton cycle between 5 bar and 1 bar pressure.Find air standard efficiency. Take γ = 1.4. 04
(b) Prove that entropy is a point function. 04
(c) Define 1] Boyle’s law 2] Charle’ law 3] Reunault’s law. 03
(d) Differentiate reversibility and irreversibility. 03
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