PTU Punjab Technical University B-Tech May 2019 Question Papers 3rd Semester Petroleum Refinary Engineering
Total No. of Pages : 02
Total No. of Questions : 09
B.Tech.(Petroleum Refinary Engineering) (2013 Onwards) (Sem.?3)
HEAT TRANSFER
Subject Code : BTPC-303
M.Code : 72192
Time : 3 Hrs. Max. Marks : 60
INSTRUCTION TO CANDIDATES :
1.
SECTION-A is COMPULSORY consisting of TEN questions carrying T WO marks
each.
2.
SECTION-B contains FIVE questions carrying FIVE marks each and students
has to attempt any FOUR questions.
3.
SECTION-C contains T HREE questions carrying TEN marks each and students
has to attempt any T WO questions.
SECTION-A
1. Answer briefly :
a. Write down Fourier, Laplace & Poisson equations of heat transfer.
b. What is critical Reynolds number?
c. "Condensing equipments are always designed for film-wise condensation" Why?
d. Define thermal diffusivity. What is its physical significance?
e. Define effectiveness and NTU of a heat exchanger.
f. Indicate the various methods of improving the overall efficiency of evaporators.
g. Discuss the advantages of a multiple effect evaporator.
h. Define Kirchhoff's law.
i. Explain the terms "Black body" and "Grey body" with reference to radiant heat
transfer.
j. Define view factor and discuss its importance.
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SFCTION-B
2.
Discuss briefly the difference between film-wise and drop-wise condensation. What are the
methods emploved to promote drop-wise condensation?
3.
Define emissive power and intensity of radiation. Obtain relation between the two.
4.
Define LMTD and explain the reason for which this concept is introduced in heat
exchanger design. Explain why correction factors are being used when applying this
technique for the design of multi-pass heat exchangers.
5.
Discuss briefly the phenomenon of nucleate and film boiling. Explain with a neat diagram
the various zones of boiling.
6.
State Dittus-Boelter equation and Colburn equation for heat transfer and discuss their
application.
SECTION-C
7.
Water flows through a cast steel pipe (k50 W/m-k) with an outer diameter of 104mm and
2mm wall thickness.
a. Calculate the heat loss by Convection and conduction per metre length of an insulated
pipe when the water temperature is 15 degree Celsius the outer air temperature is
?10 degree Celsius the water side heat transfer Coefficient is 30 kilo Watt per metre
square per Kelvin and the outside heat transfer Coefficient is 20 Watt per metre square
per Kelvin.
b. Calculate the corresponding heat loss when the pipe is lagged with insulation having an
outer diameter of 300 mm and thermal conductivity of k 0.05 Watt per metre per
Kelvin.
8.
A heat exchanger tube of D ? 20mm diameter conveys 0.0983kg/s of water
(Pr ? 4.3. k ? 0.632 W/m K, - 1000kg/m3. ? 0.651 ? 10?1 kg/ms) on the inside which is
used to cool a stream of air on the outside where the external heat transfer coefficient has a
value of h = 100 W/m2 K Ignoring the thermal resistance of the tube walls, evaluate the
overall heat transfer coefficient, U assuming that the internal heat transfer coefficient is
given by the Dittus-Boelter relation for fully) developed turbulent pipe flow.
9.
Two large parallel planes are at 1000 k and 600 k. Determine the heat exchanger per unit
area.
a. if surfaces are black.
b. if the hot one has an emissivity of 0.8 and the cooler one 0.5.
c. if a large plate is inserted between these two, the plate having an emissivity of 0.2.
NOTE : Disclosure of Identity by writing Mobile No. or Making of passing request on any
page of Answer Sheet will lead to UMC against the Student.
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This post was last modified on 04 November 2019