PPT: Fins | Heat Transfer - Mechanical Engineering PDF Download

 Page 1


• Fins are generally used to enhance the heat 
transfer from a given surface.
• Addition of fins can increase the heat transfer 
from the surface by several folds.
• Typical application areas of Fins are
HEAT TRANSFER FROM EXTENDED 
SURFACES (FINS)
Aug. 2016 MT/SJEC/M.Tech. 7
• Typical application areas of Fins are:
• Radiators for automobiles
• Air-cooling of cylinder heads of Internal 
Combustion engines (e.g. scooters, motor 
cycles, aircraft engines etc.), air compressors 
etc.
Page 2


• Fins are generally used to enhance the heat 
transfer from a given surface.
• Addition of fins can increase the heat transfer 
from the surface by several folds.
• Typical application areas of Fins are
HEAT TRANSFER FROM EXTENDED 
SURFACES (FINS)
Aug. 2016 MT/SJEC/M.Tech. 7
• Typical application areas of Fins are:
• Radiators for automobiles
• Air-cooling of cylinder heads of Internal 
Combustion engines (e.g. scooters, motor 
cycles, aircraft engines etc.), air compressors 
etc.
• Economizers of steam power plants
• Heat exchangers of a wide variety, used 
in different industries
• Cooling of electric motors, transformers 
Fins – Applications (contd.)
 
• Cooling of electric motors, transformers 
etc.
• Cooling of electronic equipments, chips, 
I.C. boards etc.
Page 3


• Fins are generally used to enhance the heat 
transfer from a given surface.
• Addition of fins can increase the heat transfer 
from the surface by several folds.
• Typical application areas of Fins are
HEAT TRANSFER FROM EXTENDED 
SURFACES (FINS)
Aug. 2016 MT/SJEC/M.Tech. 7
• Typical application areas of Fins are:
• Radiators for automobiles
• Air-cooling of cylinder heads of Internal 
Combustion engines (e.g. scooters, motor 
cycles, aircraft engines etc.), air compressors 
etc.
• Economizers of steam power plants
• Heat exchangers of a wide variety, used 
in different industries
• Cooling of electric motors, transformers 
Fins – Applications (contd.)
 
• Cooling of electric motors, transformers 
etc.
• Cooling of electronic equipments, chips, 
I.C. boards etc.
Fins of uniform cross-section 
(rectangular or circular) – Governing 
differential equation:
Q
conv
T
o
t
Y
A
c
h, T
a
 
L
dx
Q
x
Q
x+dx
w
X
X
Z
Fig. 6.2(a) Rectangular fin of uniform crosssection
Page 4


• Fins are generally used to enhance the heat 
transfer from a given surface.
• Addition of fins can increase the heat transfer 
from the surface by several folds.
• Typical application areas of Fins are
HEAT TRANSFER FROM EXTENDED 
SURFACES (FINS)
Aug. 2016 MT/SJEC/M.Tech. 7
• Typical application areas of Fins are:
• Radiators for automobiles
• Air-cooling of cylinder heads of Internal 
Combustion engines (e.g. scooters, motor 
cycles, aircraft engines etc.), air compressors 
etc.
• Economizers of steam power plants
• Heat exchangers of a wide variety, used 
in different industries
• Cooling of electric motors, transformers 
Fins – Applications (contd.)
 
• Cooling of electric motors, transformers 
etc.
• Cooling of electronic equipments, chips, 
I.C. boards etc.
Fins of uniform cross-section 
(rectangular or circular) – Governing 
differential equation:
Q
conv
T
o
t
Y
A
c
h, T
a
 
L
dx
Q
x
Q
x+dx
w
X
X
Z
Fig. 6.2(a) Rectangular fin of uniform crosssection
Fins of uniform cross-section 
(rectangular or circular) – Governing 
differential equation:
• Assumptions:
• Steady state conduction, 
with no heat generation 
in the fin
• Thickness ‘t’ is small 
 
• Thickness ‘t’ is small 
compared to length L 
and width w, i.e. one-
dimensional conduction 
in the x-direction only.
• Thermal conductivity, k 
of the fin material is 
constant.
Page 5


• Fins are generally used to enhance the heat 
transfer from a given surface.
• Addition of fins can increase the heat transfer 
from the surface by several folds.
• Typical application areas of Fins are
HEAT TRANSFER FROM EXTENDED 
SURFACES (FINS)
Aug. 2016 MT/SJEC/M.Tech. 7
• Typical application areas of Fins are:
• Radiators for automobiles
• Air-cooling of cylinder heads of Internal 
Combustion engines (e.g. scooters, motor 
cycles, aircraft engines etc.), air compressors 
etc.
• Economizers of steam power plants
• Heat exchangers of a wide variety, used 
in different industries
• Cooling of electric motors, transformers 
Fins – Applications (contd.)
 
• Cooling of electric motors, transformers 
etc.
• Cooling of electronic equipments, chips, 
I.C. boards etc.
Fins of uniform cross-section 
(rectangular or circular) – Governing 
differential equation:
Q
conv
T
o
t
Y
A
c
h, T
a
 
L
dx
Q
x
Q
x+dx
w
X
X
Z
Fig. 6.2(a) Rectangular fin of uniform crosssection
Fins of uniform cross-section 
(rectangular or circular) – Governing 
differential equation:
• Assumptions:
• Steady state conduction, 
with no heat generation 
in the fin
• Thickness ‘t’ is small 
 
• Thickness ‘t’ is small 
compared to length L 
and width w, i.e. one-
dimensional conduction 
in the x-direction only.
• Thermal conductivity, k 
of the fin material is 
constant.
Fins of uniform cross-section 
(rectangular or circular) – Governing 
differential equation:
• Assumptions (contd.):
• Isotropic (i.e. const. k in all 
directions) and homogeneous 
(i.e. const. density) material.
• Uniform heat transfer coeff. h, 
over the entire length of fin.
 
• Uniform heat transfer coeff. h, 
over the entire length of fin.
• No bond resistance in the 
joint between the fin and the 
base wall, and
• Negligible radiation effect.