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Engineering Thermodynamics : Question Paper May 2015 - Mechanical Engineering (Semester 3) | Gujarat Technological University (GTU)

## Engineering Thermodynamics - May 2015

### Mechanical Engineering (Semester 3)

TOTAL MARKS: 100
TOTAL TIME: 3 HOURS
(1) Question 1 is compulsory.
(2) Attempt any four from the remaining questions.
(3) Assume data wherever required.
(4) Figures to the right indicate full marks.
1 (a) Define property. What is meant by intensive and extensive property? State the differences between Microscopic approach and macroscopic approach.(7 marks) 1 (a) Define property. What is meant by intensive and extensive property? State the differences between Microscopic approach and macroscopic approach.(7 marks) 1 (b) State the Steady Flow Energy Equation and explain how this equation can be applied for (i) Nozzle, (ii) Boiler, and (iii) Steam Turbine.(7 marks) 2 (a) The mass flow rate of steam into a steam turbine is 1.5 Kg/s and heat loss from the turbine is 8.5 KW. The steam is entering the turbine at the pressure of 2MPa, temperature 350°C, Velocity 50 m/s, elevation 6 m/s and is leaving the turbine at a pressure of 0.1 MPa, quality of 100%, velocity of 200 m/s, elevation of 3 m/s. Determine power output of turbine.(7 marks)

### Answer any one question from Q2 (b) & Q2 (c)

2 (b) State Kelvin-Plank Statement of Second Law of thermodynamics and show that violation of Kelvin-Plank statement leading to violation of Clausius statement.(7 marks) 2 (c) A heat pump is used to heat the house in winter. A house requires 50 KJ/s heat for heating in winter which is delivered by heat pump from outside air. Work required to operate the heat pump is 8 KW. Calculate the Co-efficient of Performance of heat pump and heat abstracted from outside.(7 marks)

### Answer any two question from Q3 (a), (b) & Q3 (c), (d)

3 (a) Explain principle of increase of entropy for an isolated system.(7 marks) 3 (b) What is irreversibility? State various types of irreversibilities and explain them.(7 marks) 3 (c) Explain the concept of decrease in available energy when heat is transferred through a finite temperature difference with the aid of T-S diagram.(7 marks) 3 (d) 5 kg of water at 0°C is exposed to reservoir at 98°C. Calculate the change of entropy of water, reservoir and universe. Assume that specific heat of water is 4.187 KJ/Kg-K.(7 marks)

### Answer any two question from Q4 (a), (b) & Q4 (c), (b)

4 (a) Draw Rankine cycle on P-v, T-s and h-s diagrams and derive an expression for its thermal efficiency with and without pump work.(7 marks) 4 (b) An engine working on Diesel cycle has cylinder bore of 190 mm and piston stroke of 230 mm. The clearance volume is 290 cm3. The fuel injection takes place at constant pressure for 6% of the stroke. Determine the air standard cycle efficiency.(7 marks) 4 (c) Compare Otto, Diesel and Dual cycle for
i) Same compression ratio and heat supplied
ii) Same Max. Pressure and temperature.
(7 marks)
4 (d) Dry and saturated steam at pressure of 10.5 bar is supplied to a turbine and expanded isentropically to a pressure 0.075 bar. Calculate Thermal efficiency of Rankine cycle.(7 marks)

### Answer any two question from Q5(a), (b) & Q5 (c), (d)

5 (a) What is regeneration in gas turbine plant? How it improves thermal efficiency of simple open cycle Gas Turbine Plant. Explain it with the help of schematic diagram and T-S Diagram of the cycle.(7 marks) 5 (b) State the statements of Dalton's Law and Gibbs-Dalton Law. Explain in detail Dalton's law of partial pressures.(7 marks) 5 (c) How actual Brayton cycle differes from the theoretical cycle? Explain with the help of T-S diagram.(7 marks) 5 (d) What is the Vander waal's equation of state? State its importance and derive it.(7 marks)

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