Code No: 43017

SET-1

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JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD R07 II B.Tech. I Semester Supplementary Exams, May/June – 2009 THERMODYNAMICS (Common to ME, AE & AME) Time: 3 hours Max Marks: 80 Answer any FIVE Questions. All Questions carries equal marks. ---

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1) a) Distinguish between Microscopic and Macroscopic approaches in Thermodynamics b) Explain the following terms i) State ii) Process iii) Cycle [8+8]

2) a) What is Quasi – Static process and explain its characteristics features b) 1 Kg of a fluid is compressed reversibly according to a law PV=0.25 where ‘P’ is in bar and ‘V is in m3 /kg. The final volume is ¼ of initial volume. Calculate the work done on the fluid and sketch the process on a P-V diagram [8+8]

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3) a) Show that energy is a property of the system b) A closed system undergoes a reversible process at a constant pressure process of 3.5 bar and its volume changes from 0.15m3 to 0.06 m3. 25KJ of heat is rejected by the system during the process. Determine the change in internal energy of the system. [8+8]

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4) a) Prove the equivalence of Kelvin Planck and Clausius Statements b) Air at 15 C and 1.05 bar occupies a volume of 0.02 m3. The air is heated at constant volume until the pressure is 4.2 bar and then cooled at constant pressure back to the original temperature . calculate (i) The net heat flow to or from the air and (ii) The net entropy change, sketch the process on T-S diagram [8+8] 5) a) Why is the second law called the Law of degradation of energy b) Discuss the entropy change in a irreversible process

[8+8]

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6) a) A rigid vessel of volume 0.86m3 contains 1 kg of steam at a pressure of 2 bar. Evaluate the specific volume, temperature, dryness fraction, internal energy, enthalpy and entropy of system b) State and explain i) Dalton’s law of partial pressures ii) Avogadro’s Law [8+8]

Contd…..[2]

[Set-1]

With the help of P-V and T-S diagrams, show that for the same maximum pressure and temperature of the cycle and the same heat rejection thermal Efficiency ofdiesel > dual > Otto cycle b) Derive air standard efficiency of an otto cycle and draw its T-S diagram. [8+8]

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7) a)

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8) a) Derive Clausius – Clapeyron equation b) A car not engine working between 377 C and 37 C produces 120KJ of work. Determine i) The heat added in KJ ii) Entropy change during heat rejection process iii) The engine Thermal efficiency [8+8]

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SET-2

Code No: 43017

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JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD R07 II B.Tech. I Semester Supplementary Exams, May/June – 2009 THERMODYNAMICS (Common to ME, AE & AME) Time: 3 hours Max Marks: 80 Answer any FIVE Questions. All Questions carries equal marks. ---

What are the different types of thermodynamics systems? Explain with examples Discuss Homogenous and heterogeneous systems [8+8]

2 a)

Define the First law of Thermodynamics and discuss why it is known as Law of Conservation of energy A nozzle receives 1200 kg/h of steam at 1.3 MN/m2, specific volume 142 lit/kg, internal energy 4400 KJ/kg and negligible speed. At the exit, the pressure is 100KN/m2, specific volume 1660 lit/kg and internal energy 2200 KJ/kg. Calculate the exit velocity of the steam. [8+8]

b)

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1 a) b)

Write clausius and Kelvin- Planck statements and their equivalence Define i) Absolute thermodynamic temperature ii) Entropy iii) C.O.P

[8+8]

4 a) b)

Derive Maxwell relations Explain Gibbs and Helmholtz functions.

[8+8]

5 a)

Draw P-V and T-S diagram for water starting from its liquid phase to super heated steam. 2 m3 of air at 1.1 bar and 20 C is heated in a cylinder at constant pressure until its volume is 4.5 m3. It is then compressed according to the law PVn = constant till pressure and volume change to 5.5 bar and 0.6 m3. Calculate change in entropy, work and heat transfer during the processes and the value of n. [8+8]

b)

Describe a psychometric chart and show main properties of moist air (atmospheric) on it. Atmospheric air enters a heater at 35 C and 55% relative humidity and leaves at temperature of 40 C. Calculate: i) The enthalpy supplied to the air and ii) The final relative humidity. [8+8]

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6 a)

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3 a) b)

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b)

7

Describe the following cycles i) Dual combustion cycles ii) Sterling cycle iii) Alkinson cycle iv) Lenoin cycle [16] Cont…..[2]

[Set-2]

b)

Discuss the advantages and disadvantages of vapour absorption refrigeration system over the vapour compression system. A Bell-Coleman refrigeration cycle works between 1 bar and 5 bar. The adiabatic efficiency of compression is 85% and expansion is 90%. Find the C.O.P of the system and its tonnage when the air flow rate is 1kg/sec. The ambient temperature is 27 C and refrigerator temperature is 0 C.

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8 a)

[8+8]

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SET-3 Code No: 43017

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JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD R07 II B.Tech. I Semester Supplementary Exams, May/June – 2009 THERMODYNAMICS (Common to ME, AE & AME) Time: 3 hours Max Marks: 80 Answer any FIVE Questions. All Questions carries equal marks. --Define : Non-flow work and flow work , Extensive properties and intensive properties, Boundary and surrounding of a system [16]

2 a) b)

Derive study flow energy equation for nozzle and steam turbines A gas turbine receives gas at an enthalpy of 800 KJ/kg and a velocity of 100 m/s. The gas leaves the turbine at an enthalpy of 380 KJ/kg and a velocity of 150 m/s. Heat lost to surroundings from the gas is 36 KJ/s. if the rate of gas flow is 10 kg/s, find the power developed by the turbine [8+8]

3 a) b)

Define a heat engine and a refrigerator Prove that an engine operating between two heat reservoirs cannot have higher efficiency than that of a reversible engine operating between the same heat reservoirs [8+8] Explain availability and Irreversibility An engine working on carnot cycle receives 1020 KJ heat from a heat reservoir at a constant temperature of 950 C and rejects heat to a heat sink at a constant temperature of 30 C .Calculate i) The thermal efficiency of the engine and ii) The work done [8+8]

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4 a) b)

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1

5 a) Derive Clausius – Clapeyron equation b) State and explain i) Dalton’s law of partial pressures

Define degree of saturation, Adiabatic saturation, specific humidity and relative humidity What is the use of psychometric chart, compressibility charts and Mollier chart [8+8]

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6 a) b)

ii) Avagodro’s law [8+8]

Cont…..[2]

[Set-3]

b)

8 a)

State the methods of improving thermal efficiency of steam power plant working on Rankine vapour cycle and describe them with necessary diagrams Describe an ideal vapour compression refrigeration cycle. [8+8]

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b)

Describe Otto gas power cycle with the help of P-V and T-S diagram. Derive an expression for its all standard efficiency The compression ratio in an air standard Otto cycle is 7. At the beginning of compression process the pressure is 98 KN/m2 and temperature is 300 K. The heat added to air per cycle is 1850 KJ/kg of air. Calculate i) Thermal efficiency ii) The m.e.p of the cycle [8+8]

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7 a)

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Code No: 43017

SET-4

Explain “ internal energy”, “heat and work” Explain the zeroth law of thermodynamics

[8+8]

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1 a) b)

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JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD R07 II B.Tech. I Semester Supplementary Exams, May/June – 2009 THERMODYNAMICS (Common to ME, AE & AME) Time: 3 hours Max Marks: 80 Answer any FIVE Questions. All Questions carries equal marks. ---

2 a) prove that internal energy is a property of a thermodynamic system b) A closed system containing 0.75 kg of air at a temperature of 8oo K and pressure of 400 KN/m2 is expanded adiabatically to a final pressure of 150 KN/m2. Draw a P-V diagram for this process and calculate the work done [8+8] State Kelvin-Plank statements and Clausius statement Prove that all reversible engines operating between the same two heat reservoirs have the same efficiency [8+8]

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3 a) b)

4 a) State Clausius inequality b) Two reversible heat engines operate on carnot cycle. They work in series between a maximum and minimum temperature of 550 C and 20 C. If the engines have equal thermal efficiencies and the first rejects 450 KJ to the second, calculate i) The temperature at which heat is supplied to the second engine ii) The work done by each engine [8+8] Define dryness fraction of steam. Describe methods of finding dryness fraction of steam 10 kg of feed water is heated in a boiler at a constant pressure of 1.5 MN/m2 from 40 C. Calculate the enthalpy required and change of entropy when water is converted into following qualities of steam in each case i) Wet steam at x=0.95 and ii) Super heated steam at 300 C [8+8]

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5 a)

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b)

6 a)

b)

Define saturated air, wet bulb temperature, specific humidity and relative humidity State and explain i) Dalton’s law of partial pressure ii) Avagadro’s law [8+8] Cont…..[2]

[Set-4]

8 a) b)

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b)

Describe diesel gas power cycle with the help of P-V and T-S diagrams. Derive an expression for its air standard efficiency A diesel engine has a clearance volume of 250 cm3 and a bore and stroke of 15cm and 20cm respectively. The inlet conditions are 100KN/m2 and 20 C. The maximum temperature of the engine is 1500 C. Calculate i) Ideal thermal efficiency of cycle and ii) m.e.p [8+8]

Explain with neat sketch the working of vapour compression refrigeration cycle Describe a binary vapour cycle with the help of schematic diagram of the plant and T-S diagram of the cycle. [8+8]

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7 a)

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