Name : .
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Roll No. : .....
Invigilators Signature : ..
CS/B.TECH(NEW)/SEM-2/ME-201/2013
2013
ENGINEERING THERMODYNAMICS
& FLUID MECHANICS
Time Allotted : 3 Hours
Full Marks : 70
pap
The figures in the margin indicate full marks.
Candidates are required to give their answers in their own words
as far as practicable.
i)
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10 1 = 10
If heat engine attains 100% thermal efficiency, it violets
a)
Zeroth law of thermodynamics
b)
1st law of thermodynamics
c)
2nd law of thermodynamics
d)
none of these.
in
a c.
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ii)
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1.
GROUP A
( Multiple Choice Type Questions )
Choose the correct alternatives for any ten of the following :
The more effective way of increasing efficiency of a
Carnot engine is to
a)
increase higher temperature
b)
decrease higher temperature
c)
increase lower temperature
d)
decrease lower temperature.
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iii)
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Air standard efficiency of Otto Cycle depends on
a)
ratio of specific heats b)
cut-off ratio
c)
compression ratio
d)
both (a) and (c).
The flow field represented by the velocity vector
iv)
V = axi + by 2 j + czt 2k , where a, b and c are constants is
v)
dynamic viscosity
c)
mass density
b)
kinematic viscosity
d)
velocity of flow.
PMM-1 is impossible according to
a)
2nd law of thermodynamics
b)
3rd law of thermodynamics
c)
1st law of thermodynamics
d)
zeroth law of thermodynamics.
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vii)
a)
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vi)
a)
three-dimensional and unsteady
b)
two-dimensional and steady
c)
three-dimensional and steady
d)
two-dimensional and unsteady.
Pitot tube is used to measure
During throttling, which of the following properties does
not change ?
a)
Internal energy
b)
Entropy
c)
Pressure
d)
Enthalpy.
ix)
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in
a c.
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viii) Which fluid does not experience shear stress during
flow ?
a)
Pseudo-plastic
b)
Dilatant
c)
Inviscid
d)
Newtonian.
The differential equation of pressure variation in a static
fluid may be written as ( y measured vertically upward
and is specific weight)
a)
dP = d y
b)
dp = dy
c)
dy = dP
d)
dP = d y .
CS/B.TECH(NEW)/SEM-2/ME-201/2013
x)
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The standard atmospheric pressure is 10132 kPa. The
local atmospheric pressure at a location was 9152 kPa.
If a pressure is recorded as 2248 kPa (gauge), it is
equivalent to
xi)
xii)
a)
12380 kPa ( abs )
b)
8884 kPa ( abs )
c)
11400 kPa ( abs )
d)
6904 kPa ( abs ).
For an ideal gas, for which process can temperature of a
system decrease even if heat is added to it ?
a)
Isobaric
b)
Isothermal
c)
Isentropic
d)
Polytropic.
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The area under a curve, representing a non-cyclic
process on a temperature entropy ( T-S ) plane
represents
heat transfer for a reversible process
b)
work transfer for a reversible process
c)
heat transfer for any process
d)
work transfer for any process.
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a)
xiii) Oil spreads on the surface of water because
a)
oil is less dense than water
b)
oil is immiscible in water
c)
oil has less surface tension than water
d)
oil has low vapour pressure.
xiv) Spot the odd out.
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Thermal conductivity
b)
Kinetic energy
c)
Work
d)
Pressure.
in
a c.
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xv)
a)
An engine is supplied with 1120 kJ/s of heat and the
source and sink are maintained at constant fixed
temperatures of 560 K and 280 K respectively. If heat
rejection is 840 kJ/s, indicate the given cycle is
a)
reversible
b)
irreversible
c)
impossible
d)
unpredictable, insufficient data.
3
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GROUP B
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( Short Answer Type Questions )
Answer any three of the following
2.
3 5 = 15
A 0025 m3 vessel contains 03 kg of steam at 2 MPa.
Determine the quality, enthalpy and entropy of steam. Given
ts = 2122C, v f = 0001177 m3/kg, v g = 00995 m3/kg,
h f = 9085 kJ/kg, h fg = 18887 kJ/kg, s f = 2447 kJ/kg-K,
s fg = 3590 kJ/kg-K.
02 m3 of an ideal gas at a pressure of 2 MPa and 600 K is
expanded isothermally to 5 times the initial volume. It is then
cooled to 300 K at constant volume and then compressed
back polytropically to its initial state. Determine the net work
done and heat transfer during the cycle.
4.
At the inlet to a certain nozzle the specific enthalpy of fluid
passing is 2800 kJ/kg. The nozzle is horizontal and there is
negligible heat loss from it. (i) Find the velocity at exit of the
nozzle, (ii) If the inlet area is 900 cm2 and specific volume at
inlet is 0187 cm3/kg, find the mass flow rate, (iii) If the
specific volume at the nozzle exit is 0498 m3/kg, find the
exit area of the nozzle.
5.
a)
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3.
Derive an expression for displacement work in a process
where PV n = C .
b)
in
a c.
ut .
A paddle wheel used for mixing and stirring of fluids
turns 600 r.p.m. when 25 Nm torque is applied to it.
What is power transmitted to the liquid by the wheel ?
2+3
6.
a)
Establish the equivalence of Kelvin-Planck and Clausius
statements.
b)
A heat engine produces work equivalent to 80 kW with
an efficiency of 40%. Determine the heat drawn from the
source and rejected to the sink.
2+3
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GROUP C
( Long Answer Type Questions )
Answer any three of the following.
7.
3 15 = 45
a)
Write Bernoulli's equation, stating the assumptions.
b)
A two-dimensional flow is described in the Lagrangian
coordinate system as
x = x 0e kt + y 0 ( 1 e 1kt )
y = y 0e kt
Find the equation of path line of the particle and the
velocity components in Eulerian system.
7
A venturimeter has inlet and throat diameters of
300 mm and 150 mm. Water flows through it at the rate
of 0065 m2/s and the differential gauge is deflected
12 m. The specific gravity of the manometric liquid
is 16. Determine the coefficient of discharge of the
venturimeter.
6
a)
State and prove Pascal's law of pressure at a point of a
fluid body.
5
b)
The velocity vector for a two dimensional incompressible
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8.
c)
x
y
i +
flow field is given by V = 2
2
x 2 + y 2 j . State,
+
x
y
whether the flow field is continuous or discontinuous. 5
c)
in
a c.
ut .
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A diffuser consists of two parallel plates 20 cm in
diameter and 05 cm apart and connected to a 3 cm
diameter pipe. If the streamlines are assumed to be
radial in the diffuser, what mean velocity in the pipe will
correspond to an exit velocity of 05 m/s ?
5
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9.
What is pure substance ?
b)
What is the critical point ? State the values of critical
pressure and critical temperature of water ?
4
c)
Why is the Carnot cycle not practicable for a steam
power plant ?
3
d)
At the inlet to a certain nozzle, the enthalpy of the fluid
passing is 3000 kJ/kg and the velocity is 60 m/s. At the
discharge end, the enthalpy is 2762 kJ/kg. The nozzle
is horizontal and there is negligible heat loss from it.
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a)
Find the velocity at the exit from the nozzle.
ii)
If the inlet area is 01 m2 and the specific volume
at inlet is 0187 m3/kg, find the mass flow rate.
iii)
If the specific volume at the nozzle exit is
0498 m3/kg, find the exit area of the nozzle.
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i)
2+2+2
In a steam turbine, steam at 20 bar, 360C is expanded
to 008 bar. It then enters a condenser, where it is
condensed to saturated liquid water. The pump feeds
the water back into the boiler. Assume ideal processes,
find, per kg of steam, the net work and the cycle
efficiency.
7
b)
An air standard Otto cycle has as compression ratio
of 8, temperature and pressure at the beginning of
compression are 20C and 1 bar respectively. The
constant volume heat addition is 1800 kJ/kg. Calculate
the maximum temperature and pressure of the cycle
temperature of the end of expansion process. What are
the efficiency and mean effective pressure (m.e.p.) of the
cycle ? Cv = 0718 kJ/kg K and = 14.
8
11. a)
Two reversible heat engines are arranged in a series in
such a way that the heat rejected by the first engine is
absorbed by the second engine. The first engine receives
400 kJ of heat from a reservoir maintained at
temperature 600C, while the second engine rejects heat
6
in
a c.
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10. a)
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to a reservoir having temperature 0C. If the work
output of the first engine is twice than that of the
second, determine
b)
i)
efficiency of both the engines
ii)
heat rejected by the second engine
iii)
intermediate temperature.
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Air at temperature of 15C passes through a heat
exchanger with a velocity of 30 m/s where its
temperature is raised to 800C. It then enters a turbine
with same velocity of 30 m/s and expands until the
temperature falls to 650C. On leaving the turbine, air is
taken at a velocity of 60 m/s to a nozzle where it
expands until the temperature has fallen to 500C. If
the air flow rate is 2 kg/s, find out
the rate of heat transfer to the air in the heat
exchanger
ii)
the power output from turbine, assuming no heat
loss
iii)
the velocity at exit from nozzle, assuming no heat
loss.
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i)
Take, C p = 10005 kJ/kg K & h = C p . t ( h = enthalpy,
t = temperature)
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in
a c.
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