Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2019 Summer 7th Sem New 2170102 Theory Of Heat Transfer Previous Question Paper
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?VII(NEW) EXAMINATION ? SUMMER 2019
Subject Code:2170102 Date:14/05/2019
Subject Name:Theory of Heat Transfer
Time:02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (a) What are the modes of Heat Transfer? Also mention their governing
laws.
03
(b) Differentiate Conduction & Convection heat transfer. 04
(c) Derive general heat conduction equation in Cartesian coordinate
system.
07
Q.2 (a) Differentiate Natural & Forced Convection. 03
(b) Compare Electrical Analogy & Thermal Analogy for Plane Wall in
terms of Voltage and Temperature Difference respectively.
04
(c) 0.5cm thick glass (k= 0.78 W/mK) is exposed to air at 25? C (inner
side) with convection heat transfer coefficient of 15 W/m?K. The
outside air at -15? C with convection coefficient of 50 W/m?K.
Determine:
(1) Temperature at inner and outer glass surfaces
(2) Heat transfer rate
07
OR
(c) An outer wall of a house may be approximated by a 0.1m layer of
common brick (k= 0.7 W/m?C) followed by a 0.04m layer of Gypsum
plaster (k= 0.48 W/m?C). What thickness of loosely packed rockwool
insulation (k= 0.065 W/m?C) should be added to reduce the heat loss
or gain the wall by 80% ?
07
Q.3 (a) What are the common applications of Extended surfaces? 03
(b) What are the different types of Extended surfaces? 04
(c) Derive an expression for heat flow through Rectangular fins. 07
OR
Q.3 (a) What is (1) Prandtl Number (2) Grashoff Number & (3) Nusselt
Number?
03
(b) Briefly discuss the concept of Hydrodynamic boundary layer. 04
(c) Using Rayleigh?s Method, Prove that when a sphere of diameter ?d?,
moves with a uniform velocity ?V?, through a fluid of density ??? and
dynamic viscosity ???, the resistance ?R? will be
?? = ???? ??? ?? [
?? ?????? ]
07
Q.4 (a) Define Emissive Power & Emissivity. 03
(b) Define Absorptivity, Reflectivity & Trasnmissivity. 04
(c) A black body of total area 0.045 m? is completely enclosed in a space
bounded by 5 cm thick walls. the walls have a surface area 0.5 m? and
thermal conductivity 1.07 W/m?C. If the inner surface of the
07
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1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?VII(NEW) EXAMINATION ? SUMMER 2019
Subject Code:2170102 Date:14/05/2019
Subject Name:Theory of Heat Transfer
Time:02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
Q.1 (a) What are the modes of Heat Transfer? Also mention their governing
laws.
03
(b) Differentiate Conduction & Convection heat transfer. 04
(c) Derive general heat conduction equation in Cartesian coordinate
system.
07
Q.2 (a) Differentiate Natural & Forced Convection. 03
(b) Compare Electrical Analogy & Thermal Analogy for Plane Wall in
terms of Voltage and Temperature Difference respectively.
04
(c) 0.5cm thick glass (k= 0.78 W/mK) is exposed to air at 25? C (inner
side) with convection heat transfer coefficient of 15 W/m?K. The
outside air at -15? C with convection coefficient of 50 W/m?K.
Determine:
(1) Temperature at inner and outer glass surfaces
(2) Heat transfer rate
07
OR
(c) An outer wall of a house may be approximated by a 0.1m layer of
common brick (k= 0.7 W/m?C) followed by a 0.04m layer of Gypsum
plaster (k= 0.48 W/m?C). What thickness of loosely packed rockwool
insulation (k= 0.065 W/m?C) should be added to reduce the heat loss
or gain the wall by 80% ?
07
Q.3 (a) What are the common applications of Extended surfaces? 03
(b) What are the different types of Extended surfaces? 04
(c) Derive an expression for heat flow through Rectangular fins. 07
OR
Q.3 (a) What is (1) Prandtl Number (2) Grashoff Number & (3) Nusselt
Number?
03
(b) Briefly discuss the concept of Hydrodynamic boundary layer. 04
(c) Using Rayleigh?s Method, Prove that when a sphere of diameter ?d?,
moves with a uniform velocity ?V?, through a fluid of density ??? and
dynamic viscosity ???, the resistance ?R? will be
?? = ???? ??? ?? [
?? ?????? ]
07
Q.4 (a) Define Emissive Power & Emissivity. 03
(b) Define Absorptivity, Reflectivity & Trasnmissivity. 04
(c) A black body of total area 0.045 m? is completely enclosed in a space
bounded by 5 cm thick walls. the walls have a surface area 0.5 m? and
thermal conductivity 1.07 W/m?C. If the inner surface of the
07
2
enveloping wall is to be maintained at 215 ?C and the outer wall surface
is at 30?C, calculate the temperature of the black body. Neglect the
difference between inner and outer surface areas of enveloping
material.
OR
Q.4 (a) What is Overall heat transfer coefficient? 03
(b) Classify Heat Exchangers on the basis of its Mechanical Design. 04
(c) Derive an expression for Radiation between two non-black parallel
surfaces.
07
Q.5 (a) What do you mean by Heat Exchanger effectiveness? 03
(b) Differentiate Filmwise and Dropwise condensation. 04
(c) Derive LMTD Method. 07
OR
Q.5 (a) Define Boiling, Condensation & Evaporation? 03
(b) Discuss Fouling/Scale deposition phenomenon in Heat Exchangers.
Also state it?s Disadvantages.
04
(c) Write a short note on Boiling Phenomenon. 07
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This post was last modified on 20 February 2020