Download Model Question Paper – 1

(Page 1 of 3)
USN
IM32
B. E. Degree Third Semester End Examination (SEE), December 2013
ENGINEERING THERMODYANAMICS
(Model Question Paper – 1)
Time: 3 Hours ]
[ Maximum Marks: 100
Instructions to students:
1. Answer FIVE FULL questions.
2. Question No. 5, 6 and 7 are COMPULSORY
3. Answer ANY ONE from Question No. 1 and 2
4. Answer ANY ONE from Question No. 3 and 4
a)
1.
b)
c)
With suitable examples, distinguish between:
i) Closed and open system
ii) Path function and point function
iii) Intensive and extensive properties
A system of volume V contains a mass m of gas at a pressure p and
temperature T. The macroscopic properties of the system obey the
following relation:
( p + a / V2 ) (V- b) = mRT
where a, b, and R are constants.
Obtain an expression for the displacement work done by the system during
a constant-temperature expansion from volume V1 to volume V2.
Calculate the work done by a system which contains 10 kg of this gas
expanding from 1m3 to 10 m3 at a temperature of 293 K. Use the value a =
15.7 x 10 Nm4, b = 1.07 x 10-2 m3 and R = 0.278 kJ/ kg-K
Explain thermodynamic equilibrium.
[8 Marks]
[8 Marks]
[4 Marks]
OR
2.
a)
b)
Explain the principle and working of a constant volume gas thermometer
for temperature measurement.
The emf in millivolts in a thermocouple with the test junction at t ºC on
gas thermometer scale and reference junction at ice point is given by
e = 0.2 t – 5 X 10-4 t 2 (mV). The milli voltmeter is calibrated at ice and
steam points. What will be the reading on this thermometer when the gas
thermometer reads 50 ºC.
c)
3.
a)
[5 Marks]
[5 Marks]
State the concept of temperature and equality of temperature. Sir Issac
Newton proposed a linear temperature scale in which ice point is
designated as 0 ºN and normal human body as 12 ºN. If temperature of
normal human body is 98 ºF; obtain the relation between the Newton scale
and Fahrenheit. At what temperature will both the scales are identical
numerically.
[10 Marks]
Show that energy is a property of the system. Define specific heats at
constant volume and constant pressure.
[10 Marks]
Dr. Ambedkar Institute of Technology, Bengaluru – 560056
(An Autonomous Institution Affiliated to Visvesvaraya Technological University, Belgaum)
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b)
At the inlet to a nozzle, the enthalpy of fluid passing is 2800 kJ/kg, and the
velocity is 50 m/s.
At the discharge end the enthalpy is 2600 kJ/kg. The nozzle is
horizontal and there is negligible heat loss from it.
a. Find the velocity at the exit of the nozzle.
b. If the inlet area is 900 cm2 and the specific volume at the inlet is
0.187 m3/kg, find the mass flow rate.
c. If the specific volume at the nozzle exit is 0.498 m3/kg, find the exit
area of the nozzle.
[10 Marks]
OR
4.
a)
b)
5.
Showing the control volume, modify the SFEE for the following cases:
a. Steam turbine with negligible potential energy change if the process is
adiabatic
b. Boiler with negligible kinetic and potential energy change.
c. Horizontal steam nozzle with negligible entrance velocity of steam if
the process is non-adiabatic
d. Insulated horizontal throttle valve
a)
Explain PMM-I and PMM-II
b)
State the Clausius and Kelvin-Plank statement of second law of
thermodynamics and show their equivalence
A house requires 2 X 105 kJ/hr for heating in winter. Heat pump is
used to absorb heat from cold air outside in winter and send heat to the
house. Work required to operate the heat pump is 3 X 104 kJ/hr.
Determine: i) Heat absorbed from outside
ii) Co-efficient of performance.
c)
6.
The internal energy of a certain substance is given by
u = 3.56 Pv + 84
where u is in kJ/kg; P is in Pa; and v is in m3 / kg.
A system of gas of 3 kg expands from initial pressure of 500 kPa and
volume of 0.22 m3 to a final pressure of 100 kPa in a process described by
PV1.2 = constant.
a) If expansion is quasi-static, find heat transfer, work transfer and change
in internal energy.
b) In another process the same system expands according to the same P-v
relation as in part (a); and between same initial and final states; but heat
transfer in this case is 30 kJ. Find work transfer
c) Explain difference in work transfer in parts (a) and (b)
a)
b)
Describe Diesel Cycle with P-V and T-S diagram and derive an
expression for efficiency in terms of compression ratio, cut off ratio
and ratio of specific heats.
An engine working on an otto cycle has a volume of 0.5 m3; Pressure
1 bar and temperature 30°C at the beginning of compression. At the
end of compression stroke, pressure is 10 bar and 250 kJ of heat is
added at constant volume process. Determine: i) Percentage Clearance
ii) Air standard efficiency iii) Mean effective Pressure iv) Power
Dr. Ambedkar Institute of Technology, Bengaluru – 560056
(An Autonomous Institution Affiliated to Visvesvaraya Technological University, Belgaum)
[10 Marks]
[ 10 Marks]
[ 6 Marks]
[ 08 Marks]
[ 8 Marks]
[ 10 Marks]
[10 Marks]
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developed from 200 working cycles/min.
7.
c)
Obtain an expression for entropy change of a closed system when it
undergoes a polytropic process.
a)
Explain how morse test will help finding the indicated power of a
multicylinder engine.
During a test on a single cylinder, four stroke oil engine, the following
observations were made. Bore = 30 cm, Stroke = 45 cm, Duration of
the trial is 1 hour, Total fuel consumption = 7.6 kg, Calorific Value =
45000kJ/kg, Total revolutions made = 12000; MEP = 6 bar; Net.
Brake load = 1.47 kN; Brake drum diameter = 1.8 m; Rope diameter =
3 cm; Mass of jacket cooling water circulated = 550 kg; Water enters
at 50°C and leaves at 60°C. Total air consumption is 360 kg, Room
temperature is 20°C; Exhaust gas temperature is 300°C; Cp (gas) =
1.005 kJ/kg-K. Calculate i) Indicated Power and Brake Power
ii) Indicated thermal efficiency
iii) Mechanical Efficiency
iv) Draw heat balance on min. basis
b)
******
Dr. Ambedkar Institute of Technology, Bengaluru – 560056
(An Autonomous Institution Affiliated to Visvesvaraya Technological University, Belgaum)
[ 8 Marks]
[ 06 Marks]
[14 Marks]