University Of Pune Question Paper
S.E. (Petroleum/Petrochemical/Polymer) (Semester – II) Examination, 2011
HEAT TRANSFER
(2003 Course)
Time : 3 Hours Max. Marks : 100
Instructions : 1) Answers to the two Sections should be written in separate
books.
2) Draw neat diagrams wherever necessary.
3) Numbers to the right indicate full marks.
4) Assume suitable data if necessary.
5) Use of logarithmic table, electronic pocket calculators is
allowed.
SECTION – I
1. a) Explain the followings : 16
i) Thermal Diffusivity
ii) Newton’s Law of Cooling
iii) Stefan-Boltzmann Law of Radiation
iv) Thermal Resistance
v) Fourier’s Law of Heat Conduction
vi) Thermal Conductivity.
OR
2. a) A plane wall is 150 mm thick and its wall area is 4.5 m2. If its thermal
conductivity is 9.35 W/m °C and the surface temperatures are steady at 150 °C
and 45 °C, determine i) Heat flow across the plane wall; ii) Temperature
gradient in flow direction. 8
b) An Aluminium plate 50 mm thick whose one face is maintained at 250 °C and
other face at 50 °C. Thermal conductivity k(Al)
= 225 W/m °C, calculate the
rate of the heat transfer per unit area through the given plate. 4
c) Calculate the rate of the heat transfer per unit area through a copper plate 45 mm
thick whose one face is maintained at 350 °C and other face at 50 °C. Thermal
conductivity k(Copper) = 370 W/m °C. 4
[3962] – 347 -2-
3. a) Explain with the necessary expression the term “Logarithmic mean area for
the hollow cylinder”. 9
b) Derive the necessary expression for the heat conduction through a hollow
cylinder under the following cases i) Uniform thermal conductivity K and
ii) Variable thermal conductivity given by the equation K = K0 (1 + βT). 9
OR
4. a) A wall of a furnace is made up of inside layer of silica brick 120 mm thick
covered with a layer of magnesite brick 240 mm the temperature at the inside
surface of silica brick wall and outside surface of magnesite brick wall are at
725 °C and 110 °C respectively. The contact thermal resistance between the
two walls at the interface is 0.0035 °C/w per unit wall area. Estimate the rate
of the heat loss per unit are and temperature drop at the interface.
Thermal conductivity kSilica Brick = 1.7 W/m °C
Thermal conductivity kMagnesite Brick = 5.8 W/m °C. 10
b) Write a note on critical thickness of insulation. 8
5. a) Write a note on heat transfer by Natural Convection. Differentiate between
Natural Convection Vs Forced Convection. 12
b) Write a note on thermal boundary layer. 4
OR
6. a) Write a note on Overall Heat Transfer Coefficient. 6
b) Discuss any five dimensionless by numbers used in heat transfer studies. 10
SECTION – II
7. a) Discuss the concept of Black Body with neat diagram. 6
b) Prove that the total Emissive Power of diffuse surface is equal to π times its
Intensity of Radiation. 10
OR
-3- [3962] – 347
8. a) Write a note on Absorptivity, Reflectivity and Transmissivity of radiation and
based on above define the followings : Black Body, White Body and Opaque
Body. 10
b) Discuss in detail Kirchhoff’s law. 6
9. a) Discuss in detail Parallel, Counter flow and Cross flow heat exchangers with
neat diagrams. 9
b) Discuss with neat diagram Direct and Indirect Contact Type Heat Exchangers. 9
OR
10. a) Define the term “Logarithmic Mean Temperature Difference”. Derive the
necessary equation for the LMTD for parallel type heat exchanger. 14
b) It is desired to heat 4450 kg/h of cold benzene from 27 °C to 49 °C by using
hot toluene which is cooled from 71 °C to 38 °C. Benzene flows through the
inner pipe in counter current manner to toluene. Find the log mean temperature
difference for the given case. 4
11. Explain the following terms in detail : Evaporator Capacity, Evaporator Economy,
Boiling Point Elevation, Material and Enthalpy balances for single effect evaporator. 16
OR
12. Define evaporation with its the importance and state the classification of evaporators
and explain any one evaporator in detail. 16
—————
S.E. (Petroleum/Petrochemical/Polymer) (Semester – II) Examination, 2011
HEAT TRANSFER
(2003 Course)
Time : 3 Hours Max. Marks : 100
Instructions : 1) Answers to the two Sections should be written in separate
books.
2) Draw neat diagrams wherever necessary.
3) Numbers to the right indicate full marks.
4) Assume suitable data if necessary.
5) Use of logarithmic table, electronic pocket calculators is
allowed.
SECTION – I
1. a) Explain the followings : 16
i) Thermal Diffusivity
ii) Newton’s Law of Cooling
iii) Stefan-Boltzmann Law of Radiation
iv) Thermal Resistance
v) Fourier’s Law of Heat Conduction
vi) Thermal Conductivity.
OR
2. a) A plane wall is 150 mm thick and its wall area is 4.5 m2. If its thermal
conductivity is 9.35 W/m °C and the surface temperatures are steady at 150 °C
and 45 °C, determine i) Heat flow across the plane wall; ii) Temperature
gradient in flow direction. 8
b) An Aluminium plate 50 mm thick whose one face is maintained at 250 °C and
other face at 50 °C. Thermal conductivity k(Al)
= 225 W/m °C, calculate the
rate of the heat transfer per unit area through the given plate. 4
c) Calculate the rate of the heat transfer per unit area through a copper plate 45 mm
thick whose one face is maintained at 350 °C and other face at 50 °C. Thermal
conductivity k(Copper) = 370 W/m °C. 4
[3962] – 347 -2-
3. a) Explain with the necessary expression the term “Logarithmic mean area for
the hollow cylinder”. 9
b) Derive the necessary expression for the heat conduction through a hollow
cylinder under the following cases i) Uniform thermal conductivity K and
ii) Variable thermal conductivity given by the equation K = K0 (1 + βT). 9
OR
4. a) A wall of a furnace is made up of inside layer of silica brick 120 mm thick
covered with a layer of magnesite brick 240 mm the temperature at the inside
surface of silica brick wall and outside surface of magnesite brick wall are at
725 °C and 110 °C respectively. The contact thermal resistance between the
two walls at the interface is 0.0035 °C/w per unit wall area. Estimate the rate
of the heat loss per unit are and temperature drop at the interface.
Thermal conductivity kSilica Brick = 1.7 W/m °C
Thermal conductivity kMagnesite Brick = 5.8 W/m °C. 10
b) Write a note on critical thickness of insulation. 8
5. a) Write a note on heat transfer by Natural Convection. Differentiate between
Natural Convection Vs Forced Convection. 12
b) Write a note on thermal boundary layer. 4
OR
6. a) Write a note on Overall Heat Transfer Coefficient. 6
b) Discuss any five dimensionless by numbers used in heat transfer studies. 10
SECTION – II
7. a) Discuss the concept of Black Body with neat diagram. 6
b) Prove that the total Emissive Power of diffuse surface is equal to π times its
Intensity of Radiation. 10
OR
-3- [3962] – 347
8. a) Write a note on Absorptivity, Reflectivity and Transmissivity of radiation and
based on above define the followings : Black Body, White Body and Opaque
Body. 10
b) Discuss in detail Kirchhoff’s law. 6
9. a) Discuss in detail Parallel, Counter flow and Cross flow heat exchangers with
neat diagrams. 9
b) Discuss with neat diagram Direct and Indirect Contact Type Heat Exchangers. 9
OR
10. a) Define the term “Logarithmic Mean Temperature Difference”. Derive the
necessary equation for the LMTD for parallel type heat exchanger. 14
b) It is desired to heat 4450 kg/h of cold benzene from 27 °C to 49 °C by using
hot toluene which is cooled from 71 °C to 38 °C. Benzene flows through the
inner pipe in counter current manner to toluene. Find the log mean temperature
difference for the given case. 4
11. Explain the following terms in detail : Evaporator Capacity, Evaporator Economy,
Boiling Point Elevation, Material and Enthalpy balances for single effect evaporator. 16
OR
12. Define evaporation with its the importance and state the classification of evaporators
and explain any one evaporator in detail. 16
—————
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