Download AKTU (Dr. A.P.J. Abdul Kalam Technical University (AKTU), formerly Uttar Pradesh Technical University (UPTU) B-Tech 5th Semester (Fifth Semester) 2016-2017 Heat And Mass Transfer Nme 504 Question Paper
(FolloWing'Paper ID and Roll No. to be ?lled in your
Answer Books)
I?upcr ll) : 2012338 Roll No.
B.TECH.
R?gular Theory Examination (Odd Sem-V) 2016-17
HEAT AN D MASS TRANSFER
T ime .? 3 Hours Max. Marks : 100
Note k1) All symbols have usual meaning.
7 '- ii) ? Assume any relevant data, if missing.
Section - A
1? Attempt all parts. All parts carry equal marks. Write
answer of each part in short. ' (10><2=20)
a) Write down the de?nition of black body and gray
body. ' l
b) Write down the effect oftemperature and pressure
on thermal conductivity.
0) Counter ?ow heat exchanger is most preferred,
why?
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(1) Write down the signi?cance of Reynold?s and
Nusselt number.
e) . What are the uses of heat pipe?
f) What is the difference between pool boiling and
?ow bbiling?
g) Write a short notes on solar radiation.
h)? What is greenhouse effect?
i) De?ne ?111 radiative properties of the surface and
h ' also explain relation between them.
j) Discuss the mechanism of thermal conduction in
gases, liquids and solids.
Section - B
Note: Attempt any five questions from this section
(5X10=50)
A steam pipe of 5 cm inside diameter and 6.5 cm outside
diameter is covered with a 2.75 cm radial thickness of high
temperature insulation (k = 1.1 W/m.K). The surface heat
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transfer coef?cient for inside and outside surfaces are
4650 W/ m 2.K and '1 1.5 W/m2.k respectively. The thermal
conductivity?of the pipe material is 45 W/m.K. If the steam
temperature is 200?C and ambient air temperature is 25?C,
determine :
a) Heat transfer per meter length of pipe.
b) Temperature at the interface.
0) Overall heat transfer coef?cient.
0
A persbn is found dead at 5 pm. in a room where
temperature is 20?C. The temperature of the body is
measured. to be 25?C when found, andlthe heat transfer
coef?cient is estimated to be 8 W/m2.K. Modelling the
human body a 30 cm diameter; 1.70 m long'cylinder,
calculates actual time of death of the person. Take thermo
physical properties of the body :
K = 6.08 W/fn.K Density = 900 kg/m3 C = 4000 J/kg.K
Write down the signi?cance of NTU? method in heat
exchanger. Derive an expression of effectiveness for
counter ?ow heat exchanger by using NTU method.
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What do you mean by Lump System Analysis? Derive the
following expression for transient heat conduction
T(t)?Tw
T?T
I w
= exp(?Bi.FO)
Where symbols have their tisual meaning. Discuss the
physical signi?cance of Biot No. and Fourier No.
A steam condenser is transferring 250 KW of thermal
energy at a condensing temperature of 65?C. The cooling
water enters the condenser at 20?C with a ?ow rate of
7 500 kg/hr. Calculate the LMTD. If overall heat transfer
coef?cient for the condenser surface is 1250 W/m2 0C.
What surface area is required to handle this load? What
error would be introduced if the arithmetic mean
temperature difference is used rather than the log-mean
temperature difference?
Derive an expression for Nusseltnumber for turbulent
?ow over ?at plate using Colbum analogy.
Derive Reciprocity theorem and write down the salient
features of shape factor.
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A chemical having speci?c heat of 3.3 kJ/kg-K ?owing
at the rate of 20000 kg/hr enters a parallel flow heat
exchanger at 120?C. The ?ow rate of cooling water is
50000 kg/hr'with an inlet temperature of 20?C. The heat
transfer area is 10m2 and the Overall heat transfer
coef?cient is 1050 W/m20C. Determine :
9 The effectiveness of the heat ekehan?er.
- The output temperature of water and chemical.
Speci?c heat of the water is 4.186 kJ/kg.
Section - C
Note: Attempt any two questions from this section
10.
- ll.
(2x15=,30) ?
a) Derive an expression for energy equation of thermal
boundary layer over ?at plate.
b) Derive an expression of effectiveness for parallel
?ow heat exchanger by using NTU method.
a) Write a short notes on condensation. Describe
various regimes of boiling.
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12.
b)
a)
b)
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What is time constant? The steel ball bearings of
40 mm diameter 'and initially at uniform temperature
of 600?C are quenched in an oil bath maintained at
' 50?C temperature. The heat transfer coef?cient
between the ball bearing and oil is 325 W/mZK and
the thermodynamics properties of the bearing can
be taken as : k = 45 W/m-k and thermal diffusivity
'a = 1.25 x 10?5 mZ/s. Determine :
- The time duration for which bearing must
remain in oil to attain 225?C temperature.
- The instantaneous heat transfer rate from the
bearings when they are ?rst immersed 'in oil
and when they reach 225?C.
What is the signi?cance of Heisler chart? Describe
various types of Heisler chart. What is characteristic
length?
An egg with mean diameter of 40 mm and initially
at 20?C is placed in a boiling water pan for 4 minutes
and found to be boiled to the consumer?s taste. For
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how long should a similar egg for same consumer
'be boiled When taken from a refrigerator at 5?C.
Take the following properties for egg :
K = 10 W/m?C, p = 1200 kg/m3, c ='2 kJ/kg?C and
h = 100 W/mZOC.
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This post was last modified on 29 January 2020