ppt on transfer of heat, using fins

1. HEAT TRANSFER BY FINS
SUBMITTED BY:
SATYAM SINGH
SANJAY SHARMA
SUSHIL KUMAR
SUSHIL KUMAR SINGH

2. CONTENTS
1. What is fin…??
2. Types of fin
3. Application of fin
4. Material of fin
5. Fin performance
6. Heat dissipation from an infinitely long fin
7. Heat dissipation from a fin insulated at tip
8. Heat dissipation from a fin losing heat at tip

3. What is fin…??
A fin is a surface that extends from an object to increase the rate
of heat transfer to or from the environment by increasing
convection.
The amount of conduction, convection, or radiation of an object
determines the amount of heat it transfers.
Adding a fin to an object, increases the surface area resulting in
an effective heat transfer.

4. Types of fins
a) Rectangular/ plate fins
b) Tapered fin
c) Radial plate fins
d) Disk/ annular fins
e) Pin fins

5. APPLICATION OF FIN
Economizers for steam power plants.
Convectors for steam power plants.
Air cooled cylinders of aircraft engines, I.C. engines and air
compressors.
Electrical transformers and motors.
Cooling coils and condenser coils in refrigerators and air
conditioners.
Electronic equipment etc..

6. Economizers for steam power plants
Application of economizers in steam power-plants is to capture
the waste heat from flue gas and transfer it to the boiler feed
water.
This raises the temperature of the boiler feed water, lowering the
needed energy input.

7. Materials of fins
The most common heat sink materials are aluminium alloy has
one of the higher thermal conductivity values at 229 W/mK but is
mechanically soft.
Copper has around twice the thermal conductivity of aluminium
and faster, more efficient heat absorption. But it is more expensive
than aluminium
Applications : In industrial facilities, power plants, solar thermal
water systems, gas water heaters, forced air heating and cooling
systems, and electronic systems etc.

8. Diamond is another heat sink material, and its thermal
conductivity is about 2000 W/mK .
Lattice vibrations are responsible for diamond's very high thermal
conductivity.
Nowadays synthetic diamond is used as sub mounts for high-power
integrated circuits and laser diodes.
Composite materials, example copper tungsten, silicon carbide
Dymalloy (diamond in copper-silver alloy matrix), and E-material
(beryllium oxide in beryllium oxide in matrix) are also used.

9. Steady flow of heat along a rod
It is considered that fin protruding from a wall surface is straight.
its length is “ l ”
constant cross-sectional area “ Ac ”
and the circumferential parameter “ P ”
For rectangular fin
Ac = bt ; P = 2(b+t)
For circular fin (spine)
Ac = (π/4) × d2 ; P = πd

11. Heat from the heated wall is conducted through the fin and it is
convected from the sides of the fin to the surroundings.
So, heat conducted into the fin at plane “ l = x ” ,
Qx = -k A ( dT/ x)
where k = thermal conductivity of fin
dT = change in temp. of fin at l = x and temp. at base Tc
A = p l

13. Fin performance
The utility of a fin in dissipating a given quantity of heat is
generally assessed on the basis of the following parameters :
 Efficiency of fin
 Effectiveness of fin

14. Efficiency of fin
Fin efficiency is defined as the ratio of actual heat transfer rate to
the maximum possible heat transfer rate from the same fin.
(i.e. it would dissipate heat at maximum rate if the entire fin
surface area is maintained at the base temperature).
=

15. Effectiveness of fin
It is the ratio of the fin heat transfer rate to the heat transfer
that would exist without a fin.
=

16. Heat dissipation from an infinitely long fin
Qfin = c
(To – Ta)
where, P = circumferential parameter, m
h = convective heat transfer coefficient, W/m²K
k = thermal conductivity, W/mK
Ac = cross-sectional area, m²
To = temp. at the base of fin, K
Ta = surrounding temp. , K

17. Heat dissipation from a fin insulated at tip
Qfin = c (To – Ta) tanh ml
Heat dissipation from a fin losing heat at tip
Qfin = c (To – Ta) [tanh ml + h/km] / [1+h/mk tanh ml]

18. Thank you all for your kind attention