Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2018 Winter 5th Sem New 2153613 Basics Of Heat Transfer Previous Question Paper
1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?V (NEW) EXAMINATION ? WINTER 2018
Subject Code:2153613 Date:16/11/2018
Subject Name:Basics of Heat Transfer
Time: 10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
MARKS
Q.1 (a) Explain mode of heat transfer. 03
(b) Explain Fourier?s law and Newton?s law of cooling. 04
(c) Derive an expression for steady state heat conduction through hollow sphere. 07
Q.2 (a) What do you mean by convection? How do you differentiate between free
and force convection?
03
(b) A hot plate 1m? 1.5m is maintained at 300
0
C. Air at 20
0
C blows over the
plate. If the convective heat transfer coefficient is 20 W/m
2 0
C, calculate the
rate of heat transfer.
04
(c) Explain extended surface with different types. Derive the expression for heat
transfer from infinitely long fin.
07
OR
(c) A furnace wall is composed of 250 mm of fire bricks, 200 mm of common
brick, 50 mm of 85% magnesia and 3 mm of steel plate on outside. If the
inside surface temperature is 1800
K and outside surface temperature is 363
K, estimate the temperature between layer and calculate the heat loss.
Assure k (for fire brick) =4 W/(m.K), k (for common brick)=2.8 W/(m.K),
k (85% magnesia)=0.24 W/(m.K) and k (for steel)=240 W/(m.K).
07
Q.3 (a) List out various laws of radiation and explain any one in detail. 03
(b) Write Dittus Boelter equation to compute heat transfer coefficient. Explain all
the terms with their SI units
04
(c) Lubricating oil used in gear box of a 14000 rpm high speed blower is being
recycled continuously through a double pipe counter current heat exchanger
for cooling. The oil is cooled from 70
0
C to 40
0
C at the rate of 1000 kg/h
using water entering at 28
0
C. The water temperature at exit should not
exceed 42
0
C. The specific heat of oil is 2.05 kJ/kg
0
C and that of water is
4.17 kJ/kg
0
C. Calculate required rate of flow of water. If the heat exchanger
area is 3.0 m
3
, calculate the overall heat transfer coefficient.
07
OR
Q.3 (a) Give the physical significance of : Fourier?s Number, Biot number and
Reynolds number
03
(b) Explain hydrodynamic and thermal boundary layers. 04
(c) What is critical radius? Why it is necessary? Derive expression of critical
radius for Spherical shape.
07
Q.4 (a) Explain with neat sketch falling film evaporator. 03
(b) Explain feeding arrangements in multi effect evaporator (any one) 04
(c) What are different flow arrangements in heat exchanger? Derive the equation
for L.M.T.D. in co-current flow heat exchanger.
07
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1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?V (NEW) EXAMINATION ? WINTER 2018
Subject Code:2153613 Date:16/11/2018
Subject Name:Basics of Heat Transfer
Time: 10:30 AM TO 01:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
MARKS
Q.1 (a) Explain mode of heat transfer. 03
(b) Explain Fourier?s law and Newton?s law of cooling. 04
(c) Derive an expression for steady state heat conduction through hollow sphere. 07
Q.2 (a) What do you mean by convection? How do you differentiate between free
and force convection?
03
(b) A hot plate 1m? 1.5m is maintained at 300
0
C. Air at 20
0
C blows over the
plate. If the convective heat transfer coefficient is 20 W/m
2 0
C, calculate the
rate of heat transfer.
04
(c) Explain extended surface with different types. Derive the expression for heat
transfer from infinitely long fin.
07
OR
(c) A furnace wall is composed of 250 mm of fire bricks, 200 mm of common
brick, 50 mm of 85% magnesia and 3 mm of steel plate on outside. If the
inside surface temperature is 1800
K and outside surface temperature is 363
K, estimate the temperature between layer and calculate the heat loss.
Assure k (for fire brick) =4 W/(m.K), k (for common brick)=2.8 W/(m.K),
k (85% magnesia)=0.24 W/(m.K) and k (for steel)=240 W/(m.K).
07
Q.3 (a) List out various laws of radiation and explain any one in detail. 03
(b) Write Dittus Boelter equation to compute heat transfer coefficient. Explain all
the terms with their SI units
04
(c) Lubricating oil used in gear box of a 14000 rpm high speed blower is being
recycled continuously through a double pipe counter current heat exchanger
for cooling. The oil is cooled from 70
0
C to 40
0
C at the rate of 1000 kg/h
using water entering at 28
0
C. The water temperature at exit should not
exceed 42
0
C. The specific heat of oil is 2.05 kJ/kg
0
C and that of water is
4.17 kJ/kg
0
C. Calculate required rate of flow of water. If the heat exchanger
area is 3.0 m
3
, calculate the overall heat transfer coefficient.
07
OR
Q.3 (a) Give the physical significance of : Fourier?s Number, Biot number and
Reynolds number
03
(b) Explain hydrodynamic and thermal boundary layers. 04
(c) What is critical radius? Why it is necessary? Derive expression of critical
radius for Spherical shape.
07
Q.4 (a) Explain with neat sketch falling film evaporator. 03
(b) Explain feeding arrangements in multi effect evaporator (any one) 04
(c) What are different flow arrangements in heat exchanger? Derive the equation
for L.M.T.D. in co-current flow heat exchanger.
07
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2
OR
Q.4 (a) Explain construction and working of plate heat exchanger with neat sketch. 03
(b) Explain boiling point elevation and duhring?s rule 04
(c) Derive the expression for Reynolds analogy. 07
Q.5 (a) Elaborate the concept of Black Body and Grey Body. 03
(b) Explain film wise and drop wise condensation. 04
(c) Explain shell and tube heat exchanger. 07
OR
Q.5 (a) Explain the construction and working of calendria type evaporators 03
(b) What is evaporation economy? Which are the different method for increase
economy?
04
(c) What is condensation? What are the different factors which affects
condensation?
07
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This post was last modified on 20 February 2020