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Posted Date: 29 Jul 2008 Posted By: kondapalli Member Level: Gold
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2007 Jawaharlal Nehru Technological University B.Tech Mechanical Engineering THERMODYNAMICS setno3 Question paper
1. (a) Distinguish between closed and open systems by giving practical examples.
(b) A computer in a closed room of volume 200m3 dissipates energy at a rate of
10kW. The room has 50kg wood, 25kg steel and with all material at 3000k;
100kpa. Assume all the mass heats up uniformly, how long will it take to
increase the temperature 100c. [8+8]
2. (a) Derive the governing equation for the adiabatic process.
(b) Explain joules experiment in detail. [10+6]
3. (a) State and prove Clausius inequality and hence deduce that the property en-
tropy exist.
(b) A cylinder contains 0.5m3 of a gas at 0.1 MPa and 900C,. The gas is com-
pressed to a volume of 0.125m3. The final pressure is 800 kPa. Determine
the heat transferred and the change in entropy of the gas during the process.
Assume R = 0.287 kJ/kgK and Cv = 0.713 kJ/kgK [8+8]
4. (a) Show that available energy decreases during heat transfer through finite tem-
perature difference.
(b) A mass of 6.98 kg of air is in a vessel at 200 kPa and 270C . Heat is transferred
to the air from a reservoir at 7270C until the temperature of the air rises to
3270C. The environment is at 100kPa, 170C . Determine
i. the initial and final availability of air and
ii. the maximum useful work associated with the process. Assume for air
Cp= 1.005 kJ/kg.K and R = 0.287kJ/kg.K. [8+8]
5. (a) List out the various non - flow processes when the First law of thermodynamics
is applied to closed system.
(b) Derive the relationship between the two principle specific heats and charac-
teristic gas constant for a perfect gas.
(c) Find the molecular weight and gas constant for the gas whose specific heats
are as follows:
Cp = 1.967KJ/KgK Cv = 1.507 KJ/KgK [6+4+6]
6. (a) Prove :specific humidity= 0.622 pv/(p-pv) assuming air as an ideal gas of
molecular weight 28.966.
1 of 2
Code No: RR210304 Set No. 3
(b) A mixture of hydrogen and oxygen is in the ratio of 2 to 1 by volume .determine
the mass of hydrogen required and volume of the container per kg of oxygen
if the temperature and pressure of the mixture are to be 100kPa and 300kPa
respectively. [6+10]
7. (a) What do you mean by air standard cycles? What are the assumptions for air
standard cycles.
(b) An air standard Otto cycle has a compression ratio of 8. At the start of the
compression process, the temperature is 260C and the pressure is 1 bar. If the
maximum temperature of the cycle is 10800C calculate
i. The heat supplied per kg of air
ii. The network done per kg of air
iii. The thermal efficiency of the cycle. [6+10]
8. A refrigerant R-12 vapour compression system operating at a condenser tempera-
ture of 400C and an evaporator temperature of -50C develops 15 tons of refrigera-
tion. Using p-h chart for R-12, determine:
(a) The mass low rate of refrigerant circulated
(b) The theoretical piston displacement of compressor and piston displacement
per ton of refrigeration.
(c) The theoretical horsepower of the compressor and horsepower per ton of re-
frigeration.
(d) The heat rejected in the condenser and
(e) The car not C.O.P. and actual C.O.P. of the cycle. [16]
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