AMIE Question Papers (Thermal Science and Engineering)

91 Pages·2015·3.67 MB·English

AMIE Study Material & Admission Packages AMIE(I) Study Circle, Roorkee www.amiestudycircle.com
W'05 : 6 AN : MC 405 C1498t
TIIERMAL SCIENCE AND ENGINEERING
./ Time : Tbree hours
Maximum marks : 1 ()()
Answer FIVE questions, taldng ANY TW() from Group A,
ANY TWO from Group B and AIL from Group C.
A/1 parts ofa question (a, b, etcJ should be
answered at one place.
Answer should be briefa nd to-the-point and be supple
mented with neat sketches. Unnecessary long answers
may result in Joss ofm arks.
Any missing data or wrong data may be assumed suitably
giving proper justification.
Figures on the right-hand side margin indicate fuU marks.
Use ofMollier Chart and Steam Tables are permitted
Group A
1. (a) Define property and mention its main characteristic
in relation to a cyclic process. 4
(b) In what respects are the heat and work interactions
( tl similar and ( ii) dissimilar ? 4
(TurnOver'

AMIE(I) STUDY CIRCLE, SECOND FLOOR, SULTAN TOWER, ROORKEE - 247667 (UTTARANCHAL)
EMAIL: [email protected] Ph: [phone], 9412903929, 9897394020
1
AMIE Study Material & Admission Packages AMIE(I) Study Circle, Roorkee www.amiestudycircle.com
(c) It is desired to compress 10 kg of gas from 1 ·5m3 (ii) turbine shaft work
to 0 ·3m3 at a constant pressure of 15 bar. During
(iii) power required to drive the pump
this compression process, the temperature rises from
20°C to 150°C and the increase in internal energy (iv ) work ratio
is 3250 kJ. Calculate the work done, heat ~eraction
and change in enthalpy during the process. AISb work ( v) Rankine efficiency
out the average value of specific heat at constant
pressure. 12 ( vi) heat flow in the condenser. 12
2. {a) State and prove Camot theorem. 6 4. (a) Describe a simple vapour compression cycle giving
clearly the flow diagram. 4
( b ) What does the principle of entropy increase,
specify? 2
(b) Define dry-bulb temperature and the wet-bulb
(c) A reversible heat engine receives heat from a high temperature. When do these become equal to each
temperature reservoir at T, K and rejects heat to a other? 3
low temperature sink of 800 K. A second reversible
engine receives the heat rejected by the first engine ( c) What are the two basic types oflriternal combustion
at 800 K and rejects to a cold reservoir at 280 K. Make engines'? ·what are the fundamental differences
calculations for temperature T : ( i) for equal thermal between the two ? 3
1
efficiencies of the two engines, ( ii) for the two engines
to deliver the same amount of work. 12 ( d) The steam consumption of a 20 BHP double acting,
non-condensing steam engine is 9 kg/BHP /hr. The
3. {a) Derive Clapeytron's equation. What is its use and
pressure of the exhaust steam is 1 · 2 ata and quality
limitations ? 4
is 0 · 85 dry. If the diameter of the exhaust pipe is
•
(b} How does Rankine cycle differ from Camot cycle for
l5 em, what will be the velocity of steam in the exhaust
a vapour? 4
pipe, when the engines develops 18 BHP ? 1 0
(c) A steam turbine working a Rankjne cycle is supplied
dry GroupB
with saturated steam at 25 bar and the exhaust
takes place at 0 · 2 bar. For a steam flow rate of
5. (l!) Write down unsteady state three-dimensional heat
lOkg/s, determine
conduction equation in re..:;t~gular coordinates with
(i} quality of steam at end of expansion heat generator and give the meaning of each term. 5
6AN: MC 405 (1498) ( 2 ) ( Continued)
611.i'-l: lv1C 405 (1498) ( 3 ) (Tum Over)

AMIE(I) STUDY CIRCLE, SECOND FLOOR, SULTAN TOWER, ROORKEE - 247667 (UTTARANCHAL)
EMAIL: [email protected] Ph: [phone], 9412903929, 9897394020
2
AMIE Study Material & Admission Packages AMIE(I) Study Circle, Roorkee www.amiestudycircle.com
(b) An aluminium ( lc. = 204 W /mK.) rod 2 em in diameter (c) How can one determine the fouling factor of a heat
exchanger? 2
and 20cm long protrudes from a wall which is
maintained at 300 .. C. The end of the rod is insulated
(d) WhatisDcttus-Boelter's equation? Where and when
and the surface of the rod is exposed to air at 30 .. C.
does it apply ? 2
The convective heat transfer coefllcient between the
(e) Define Grashof number and explain its significance
rods surface and air is 10 W /m2 K.. Calculate the heat
in free convection heat transfer. 2
lost by the rod. Also calculate the temperature of the
oc
rod at a distance of 10 em from the wall. 15 (f) It is desired to cool oil from 120 to 50 .,C using
a double-pipe heat exchanger. The cooling water
6. (a) Explain the following: 2x7
enters the heat exchanger at 20 .,C and leaves it at 40 .. C.
Calculate the LMTD for
(i) Black body radiation
(i) a parallel-flow heat exchanger, and
(if) Reflectivity _
(ii) for a countercurrent heat exchanger. 10
(iii) Transmissivity
8. (a) What is meant by film condensation and drop-wise
(iv) Absorptivity
condensation ?. 4
";
( v) Kirchoff's law ·
(b) Distinguish b.etween nucleate boiling and film boiling. 4
( vi) Gray body
(c) A tube of 2m length and 25 mm outside diameter
is to be used to condense saturated stream at 100 OC
( vii) Emissivity.
while the tube surface is maintained at 92 OC. Estimate
( b} A steel tube, 0 · 05 m diameter, 4 · 0 m length, at the average heat transfer coefficient and rate of
temperature 600 K is located in ( i) a large brick room, conden,~anon of steam if the tube is kept horizontal.
having wall ~mperature ~00 K, ( ii ) in a brick conduct The steam condenses on the outside of the tube. Use
of size 0 · 4 m x 0 · 4 m at 300 K. Estimate the heat the data given below :
loss by radiation in each case. Take emissivity of steel At 96°C:
as 0 · 8, for rough red brick 0 · 93 respectively. 6 kr=O·OSW!mK
!.l r= 293 ·4 x 10-6 Ns/m2
7. (a) Define the effectiveness of a heat exchanger. 2
and Q = 961 kg/m3
( b ) Define the Lo.g Mean Temperature Difference At 100°C, htg = 2257 kJ/kg.
2
(L~). 12
6AN: MC 405 (1498) ( 4 ) (Continued) 6AN: MC 405 (1498) 5 (TurnOver)

AMIE(I) STUDY CIRCLE, SECOND FLOOR, SULTAN TOWER, ROORKEE - 247667 (UTTARANCHAL)
EMAIL: [email protected] Ph: [phone], 9412903929, 9897394020
3
AMIE Study Material & Admission Packages AMIE(I) Study Circle, Roorkee www.amiestudycircle.com

AMIE(I) STUDY CIRCLE, SECOND FLOOR, SULTAN TOWER, ROORKEE - 247667 (UTTARANCHAL)
EMAIL: [email protected] Ph: [phone], 9412903929, 9897394020
4
AMIE Study Material & Admission Packages AMIE(I) Study Circle, Roorkee www.amiestudycircle.com

AMIE(I) STUDY CIRCLE, SECOND FLOOR, SULTAN TOWER, ROORKEE - 247667 (UTTARANCHAL)
EMAIL: [email protected] Ph: [phone], 9412903929, 9897394020
5
AMIE Study Material & Admission Packages AMIE(I) Study Circle, Roorkee www.amiestudycircle.com

AMIE(I) STUDY CIRCLE, SECOND FLOOR, SULTAN TOWER, ROORKEE - 247667 (UTTARANCHAL)
EMAIL: [email protected] Ph: [phone], 9412903929, 9897394020
6
AMIE Study Material & Admission Packages AMIE(I) Study Circle, Roorkee www.amiestudycircle.com

AMIE(I) STUDY CIRCLE, SECOND FLOOR, SULTAN TOWER, ROORKEE - 247667 (UTTARANCHAL)
EMAIL: [email protected] Ph: [phone], 9412903929, 9897394020
7
AMIE Study Material & Admission Packages AMIE(I) Study Circle, Roorkee www.amiestudycircle.com
(c) The distance of the sun from the earth is 150 x 1 06
7. (a ) What is the effect of inclination of a tube or plate km. If the radius of the sun is 0·7 x 106 km and its
on the average condensation heat transfer coeffi-
temperature is 6200 K, estimte approximately the
cient? 3
mean temperature of the earth. Assume that the rate
of radiative transfer from the sun to the earth is equal
(b) The maximum allowable surface temperature of an
to the radiant transfer from the earth to the outer
electrically heated vertical plate 15 em high and 10 em
space which is at 0 K. Consider the earth and the sun
wide is 140 °C. Estimate the maximum rate of heat
as black bodies. 7
dissipation from both sides of the plate in an
atmosphere at 20 °C. The radiation heat transfer Group C
coefficient is 8·72 W/m2K. For air at 80°C, take
9. Choose the correct answer: 1 X 20
v=21·09x10-6 m2/s, Pr=0·692 and K=0·03
W/mK. 7 ( i) In the absence of any unbalanced force within the
system itself and also between the system and the
(c) The crank case of an automobile is 80 em long, 30 em surroundings, the system is said to be in
wide and 10 em deep. Find the rate of heat flow from
(a ) thermal equilibrium
the crank case to the atmosphere when the auto
mobile is moving at 90 km/hr. Assume that the vibra (b) mechanical equilibrium
tion of the engine and the chassis induce the transition (c) chemical equilibrium
from laminar to turbulent boundary layer over the (d) phase equilibrium
entire surface. Also, find the drag force on the total
(.zi) A process, which is defined by the locus of all the
surface of the crank case.
equilibrium points passed through by the system, is
Take the same average convective heat transfer
known as
coefficient and average shear stress for front and rear
surface'l as for the bottom and the sides. Crank case (a ) static process
surface temperature is 75 OC and atmospheric air (b) dynamic process
oc
temperature is 5 OC. At 40 for properties of
(c) quasi~static process
air, take g= 1·128 kg/m3, CP= 1007 J/kgK, (d) none of the above
!l = 19·1 x 10-6 kg/ms, K = 0·0285 W /mK. I 0
(iii) The triple point of water is
8. (a) For a balanced counterflow heat exchanger where
(a) 273K
mh Ch = the Cc, show that the temperature profiles of
(b) 273·16K
the two fluids along the heat exchanger are linear
(c) 273·02K
and parallel. 6
( d ) none of the above
(b) State and explain the reciprocity theorem in
connection with radiation hen transfer. 7 MC405(1498) ( 7 ) ( Continued )
MC405(!49i<) ( 6 ) (Cominued)

AMIE(I) STUDY CIRCLE, SECOND FLOOR, SULTAN TOWER, ROORKEE - 247667 (UTTARANCHAL)
EMAIL: [email protected] Ph: [phone], 9412903929, 9897394020
8
AMIE Study Material & Admission Packages AMIE(I) Study Circle, Roorkee www.amiestudycircle.com

AMIE(I) STUDY CIRCLE, SECOND FLOOR, SULTAN TOWER, ROORKEE - 247667 (UTTARANCHAL)
EMAIL: [email protected] Ph: [phone], 9412903929, 9897394020
9
AMIE Study Material & Admission Packages AMIE(I) Study Circle, Roorkee www.amiestudycircle.com

AMIE(I) STUDY CIRCLE, SECOND FLOOR, SULTAN TOWER, ROORKEE - 247667 (UTTARANCHAL)
EMAIL: [email protected] Ph: [phone], 9412903929, 9897394020
10