R07
Code No: X0324
SET - 1
II B. Tech I Semester Supplementary Examinations Dec - 2013
THERMODYAMICS
(Com. to ME, AE, AME)
Time: 3 hours
Max. Marks: 80
Answer any FIVE Questions
All Questions carry Equal Marks
1. a) What do you understand by macroscopic and microscopic view points?
b) A piston-cylinder device operates 1 kg of fluid at 20 atm. pressure. The initial volume is
0.04 m3. The fluid is allowed to expand reversibly following a process PV 1.45 = constant so
that the volume becomes double. The fluid is then cooled at constant pressure until the
piston comes back to the original position. Keeping the piston unaltered, heat is added
reversibly to restore it to the initial pressure. Calculate the work done in the cycle.
2. a) What is the zeroth law of thermodynamics?
b) Air flows steadily at the rate of 0.5 kg/s through an air compressor, entering at 7 m/s
velocity,100 kPa pressure, and 0.95 m3/kg volume, and leaving at 5 m/s,700 kPa, and 0.19
m3/kg. The internal energy of the air leaving is 90 kJ/kg greater than that of the air entering.
Cooling water in the compressor jackets absorbs heat from the air at the rate of 58 kW.
Compute the rate of shaft work input to the air in kW and find the ratio of the inlet pipe
diameter to outlet pipe diameter.
3. a) What are Helmholtz function and Gibbs function?
b) In a Carnot cycle, heat is supplied at 350 0C and rejected at 270C.The working fluid is water
which, while receiving heat, evaporates from liquid at 3500C to steam at 3500C.The
associated entropy change is 1.44 k J/kg K. If the cycle operates on a stationary mass of 1 kg
of water, how much is the work done per cycle and how much is the heat supplied?
4. a) Draw the T-S diagram for a pure substance and Explain.
b) Steam flows in a pipeline at 1.5 MPa. After expanding to 0.1 MPa in a throttling calorimeter,
the temperature is found to be 1200C.Find the quality of steam in the pipeline. What is the
maximum moisture at 1.5 MPa that can be determined with this set-up if at least 50C of
superheat is required after throttling for accurate reading?
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Code No: X0324
R07
SET - 1
5. a) Explain Perfect gas behavior and equations of state.
b) A mixture of 80 % CO2 and 20 % CH4 (mass basis) is maintained at 310.94 K, 86.19 bar, at
which condition the specific volume has been measured as 0.006757 m 3/kg. Calculate the
perfect deviation if the specific volume had been calculated by Vander Waals’ equation of
state.
6. a) State Dalton’s law of partial pressures.
b) Explain briefly Internal energy, enthalpy and specific heats of gas mixtures.
7. a) Derive the expression for Carnot Cycle Efficiency with neat P-V and T-S diagrams.
b) An engine equipped with a cylinder having a bore of 15 cm and a stroke of 45 cm operates
on an Otto cycle. If the clearance volume is 2000 cm3, compute the air standard efficiency.
8. a) How does Brayton cycle compare with Rankine cycle?
b) A vapour-compression heat pump system uses R-12 as the working fluid. The refrigerant
enters the compressor at 2.4 bar, 00C with a volumetric flow rate of 0.6m3/min.
Compression is adiabatic to 9 bar, 600C and the saturated liquid exits the condenser at 9 bar.
Determine the power input to the compressor and the Coefficient of performance?
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R07
Code No: X0324
SET - 2
II B. Tech I Semester Supplementary Examinations Dec - 2013
THERMODYAMICS
(Com. to ME, AE, AME)
Time: 3 hours
Max. Marks: 80
Answer any FIVE Questions
All Questions carry Equal Marks
1.
a) What is a thermodynamic system? Define an isolated system.
b) An engine cylinder has a piston of area 0.12 m3 and contains gas at a pressure of 1.5 Mpa.
The gas expands according to a process which is represented by a straight line on a
pressurevolume diagram. The final pressure is 0.15 MPa. Calculate the work done by the gas
on the piston if the stroke is 0.30 m.
2. a) State the first law for a closed system undergoing a change of state.
b) In a gas turbine the gas enters at the rate of 5 kg/s with a velocity of 50 m/s and enthalpy of
900 k J/ kg and leaves the turbine with a velocity of 150 m/s and enthalpy of 400 k J/ kg.
The loss of heat from the gases to the surroundings is 25 k J/kg. Assume for gas R = 0.285 k
J/kg
K and Cp=1.004 k J/kg K and the inlet conditions to be at 100 k Pa and 27 0C.
Determine the power output of the turbine and the diameter of the inlet pipe.
3. a) Give the expression for reversible work done by a closed system if it interacts only with the
surroundings.
b) In a steam generator, water is evaporated at 260 0C, while the combustion gas (Cp=1.08
kJ/ kg K) is cooled from 13000C to 3200C.The surrounding are at 300C.Determine the loss in
available energy due to the above heat transfer per kg of water evaporated.(Latent heat of
vaporization of water at 2600C=1662.5 k J/kg.)
4. a) Draw h-s diagram for a pure substance?
b) Steam flows in a pipeline at 1.5 MPa. After expanding to 0.1 MPa in a throttling calorimeter,
the temperature is found to be 1200C. Find the quality of steam in the pipeline. What is the
maximum moisture at 1.5 MPa that can be determined with this set-up if at least 50C of
superheat is required after throttling for accurate readings?
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Code No: X0324
R07
SET - 2
5. a) Explain various non-flow process and its properties.
b) Explain the throttling process with neat sketch.
6. a) What is a mole? What is Avogadro’s law?
b) A constant volume chamber of 0.3 m3 capacity contains 1 kg of air at 50C.Heat is transferred
to the air until the temperature is 1000C. Find the work done, the heat transferred, and the
change in internal energy, enthalpy and entropy.
7. a) Write the comparison of Otto, Diesel, and Dual cycles with neat diagram.
b) In an air standard Diesel cycle, the compression ratio is 15.Compression begins at 0.1 MPa,
400C. The heat added is 1.675 MJ/kg. Find the maximum temperature of the cycle and the
work done per kg of air.
8.
a) What is the effect of regeneration on Brayton cycle efficiency? Define the effectiveness of
a regenerator.
b) In an ideal Brayton cycle, air from the atmosphere at 1 atm, 300 K is compressed to 6 atm
and the maximum cycle temperature is limited to 1100 K by using a large air-fuel ratio. If
the heat supply is 100 MW, find the thermal efficiency of the cycle, work ratio, power
output and energy flow rate of the exhaust gas leaving the turbine.
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R07
Code No: X0324
SET - 3
II B. Tech I Semester Supplementary Examinations Dec - 2013
THERMODYAMICS
(Com. to ME, AE, AME)
Time: 3 hours
Max. Marks: 80
Answer any FIVE Questions
All Questions carry Equal Marks
1.
a) How can a closed system and its surroundings interact? What is the effect of such
interactions on the system?
b) A pump discharge a liquid into a drum at the rate of 0.032 m2/ s. The drum, 1.50 m in
diameter and 4.20 m in length, can hold 3000 kg of the liquid. Find the density of the liquid
and the mass flow rate of the liquid handled by the pump.
2. a) State the first law for a closed system undergoing a cycle with some examples.
b) A nozzle is a device for increasing the velocity of a steadily flowing stream. At the inlet to a
certain nozzle, the enthalpy of the fluid passing is 3000 k J/kg and the velocity is 60 m/s. At
the discharge end, the enthalpy is 2762 k J/ kg. The nozzle is horizontal and there is
negligible heat loss from it. Find the velocity at exit from the nozzle. If the inlet area is 0.1
m2 and the specific volume at inlet is 0.187 m3/kg, find the mass flow rate.
3. a) Explain what do you understand by the entropy Principle.
b) A pressure vessel has a volume of 1 m3 and contains air at 1.4 Mpa, 1750C. The air is cooled
to 250C by heat transfer to the surrounding at 25 0C. Calculate the availability in the initial
and final states and the irreversibility of this process. Take Po Atmospheric pressure is 100 k
Pa.
4. a) What is the critical stage? Explain the terms critical pressure, critical temperature and critical
volume of water.
b) The following data were obtained with a separating and throttling calorimeter:
Pressure in pipeline
Condition after throttling
During5 min moisture collected in the separator
Steam condensed after throttling during 5min
Find the quality of steam in the pipeline.
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1.5 Mpa,
0.1Mpa, 1100C.
0.150 litre at700C.
3.24 kg
Code No: X0324
R07
SET - 3
5. a) Ten moles of an ideal gas with specific heat ratio(γ) =1.4, is compressed reversibly and
adiabatically from 100 kPa and 270C to 1 Mpa. Determine the work done on the gas, the
change in the internal energy and the final temperature of the gas.
b) Explain types of free expansion process with some examples?
6. a) Explain what you understand by dry bulb and wet bulb temperature.
b) A sling psychrometer reads 400C dry bulb temperature and 360C wet bulb temperature. Find
the humidity ratio, relative humidity, dew point temperature, specific volume, and enthalpy
of air.
7. a) 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, η Diesel > η Dual > η Otto.
b) An air standard limited pressure cycle has a compression ratio of 15 and compression begins
at 0.1 MPa, 400C. The maximum pressure is limited to 6 MPa and the heat added is 1.675
MJ/kg. Compute the heat supplied at constant volume per kg of air and find work done per
kg of air.
8. a) Explain the vapour compression cycle with the help of flow, T-S and p-h diagrams. Can this
cycle be reversible? If not, why?
b) A refrigerator uses R-134a as the working fluid and operates on an ideal vapor compression
cycle between 0.14 Mpa and 0.8 Mpa. If the mass flow rate of the refrigerant is 0.06 kg/s,
determine the rate of heat removal from the refrigerated space and the power input to the
compressor, and find out COP?
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R07
Code No: X0324
SET - 4
II B. Tech I Semester Supplementary Examinations Dec - 2013
THERMODYAMICS
(Com. to ME, AE, AME)
Time: 3 hours
Max. Marks: 80
Answer any FIVE Questions
All Questions carry Equal Marks
1. a) What do you understand by path function and point function? What are exact and inexact
differentials?
b) The following data refer to a 12-cylinder, single-acting, two-stroke marine diesel engine:
Speed-150 rpm
Cylinder diameter- 0.8 m
Stroke of piston-1.2 m
Area of indicator diagram-5.5 x 10-4 m2
Length of diagram-0.06 m
Spring value-147 MPa per m
Find the net rate of work transfer from the gas to the pistons in kW.
2. a) Explain the system approach and the control volume approach in the analysis of a flow
process?
b) A gas of mass 1.5 kg undergoes a quasi-static expansion which follows a relationship
p = a +bV, where a and b are constants. The initial and final pressures are 1000 k Pa and
200 k Pa respectively and the corresponding volumes are 0.20 m3 and 1.20 m3.The specific
internal energy of the gas is given by the relation u = (1.5 pv -85) kJ/kg
Where p is the k Pa and v is in m 3/kg. Calculate the net heat transfer and the maximum
internal energy of the gas attained during expansion.
3. a) Give the criteria of reversibility, irreversibility and impossibility of a thermodynamic cycle
b) A Carnot cycle engine receives and rejects heat with a 200C temperature differential between
itself and the thermal energy reservoirs. The expansion and compression processes have a
pressure ratio of 50.For 1 kg of air as the working substance, cycle temperature limits of
1000 K and 300 K and T0 = 280 K, determine the second law efficiency.
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Code No: X0324
R07
SET - 4
4. a) What are saturation states? What do you understand by triple point?
b) Steam at 0.8 MPa, 2500C and flowing at the rate of 1 kg/s passes into a pipe carrying wet
steam at 0.8 MPa, 0.95 dry. After adiabatic mixing the flow rate is 2.3 kg/s. Determine the
condition of steam after mixing. The mixture is now expanded in a frictionless nozzle is
entropically to a pressure of 0.4 MPa. Determine the velocity of the steam leaving the
nozzle. Neglect the velocity of steam in the pipeline.
5. a) Explain types of free expansion processes in thermodynamics.
b) With help of neat sketch explain heat and work transfer with some examples.
6. a) Define dew point temperature? What is a psychrometer?
b) Air at 400C dry bulb temperature and 270C wet bulb temperature is to be cooled and
dehumidified by passing it over a refrigerant -filled coil to give a final condition of 15 0C
and 90 % RH. Find the amounts of heat and moisture removed per kg of dry air.
7. a) State the four processes that constitute the Ericsson cycle. Show that the regenerative
Ericsson cycle has the same efficiency as the Carnot cycle.
b) In a Stirling cycle the volume varies between 0.03 and 0.06 m3, the maximum pressure is 0.2
MPa, and the temperature varies between 540 0C and 2700C.The working fluid is air (an
ideal gas). Find the efficiency and the work done per cycle for the simple cycle.
8. a) Explain the Bell-Coleman cycle with neat diagram.
b) A vapour compression refrigeration system uses R-12 and operates between pressure limits
of 0.745 and 0.15 MPa. The vapour entering the compressor has a temperature of - 100C
and the liquid leaving the condenser is at 280C.A refrigerating load of 2 k W is required.
Determine the COP and the swept volume of the compressor if it has a volumetric efficiency
of 76 % and runs at 600 rpm.
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