information about peltier effect

1. Muhammad Umair (15261509-048)
Sana Nazir (15261509-077)
Maryam Butt (15261509-080)
Saba Mazhar (16341509-003)
Presented by:

2. Peltier’s Effect

3. History:
 In1834, a Frenchwatchmaker and part time physicist, Jean
Charles AthanasePeltier foundthat an electrical current would
produce heating or cooling at the junctionof two dissimilar
metals.
 In1838 Lenz showedthat depending on thedirection of
current flow, heat couldbe either removed froma junction to
freeze waterinto ice, or by reversing the current, heat can be
generated to melt ice.

4. What is Peltier’s Effect?
 The Peltier effect is the presence of heatingor cooling at an electrified
junctionof two different conductors.
 The Peltier effect is a temperature difference createdby applying a
voltage between two electrodes connected to a sampleof semiconductor
material.
 Electrodes (a conductor through which electricity enters or leaves an
object, substance, or region).
 Semiconductor material(a solid substance that has a conductivity
betweenthat of an insulator andthat of most metals, either due to the
additionof an impurity or because of temperature effects).

5. This phenomenoncan be useful when it is necessary to transfer heat from one
mediumto another on a small scale

6. Peltier’s Effect Process:

7. Equation:
 When a currentis made to flow through a junctionbetween
two conductors, A and B, heat may be generated or removedat
the junction. The Peltier heat generatedat the junction per unit
time, Q˙
Q˙ = ( Π A − Π B )I
where Π A, Π B is the Peltier coefficient of
conductor A and B, and I is the electric current
(fromA to B).

8. Cont…
 The total heat generatedis not determinedby the Peltier effect
alone, as it may also be influenced by Joule heating.

9. Explanation of peltier’s effect
 Consider a Cu-Fe thermocuple having boththe
junction at the same temperature. If current is passed
throughthis thermocouple in the direction as shown, heat
is evolvedat the junction A and absorbed at the junction
B.
 Therefore, junction A is heated whilethe junction B is
cooled.

10. Cont…
 If current in the circuit is reversed, thermoelectric effect
is also reversed i.e., junction B is heatedand junction A is
cooled.
 When two dissimilar metal are joined, contact potential
difference is establishedat the junction i.e. potential of the
one metal becomes above that of the other.
 In the case Cu-Fe thermocouple, the potential of Fe is
above that of Cu.

11. Cont…
 At the junction B, current flows fromCu to Fe i.e. fromlower
potential to higher potential. Hence, energyis required for this
purpose. As a result, energy is absorbedfromthe junction and it
is cooled.
 At the junction A , current flows fromFe to Cui.e. fromhigher
potential to lower potential. Hence, energy is givenout at this
junction. Consequently, junction A becomes hot.

12. Cont…
 Peltier effect is reversible. If the direction of current
throughthe thermocouple is reversed, the heat is evolved
and absorbed at the junction are also interchanged.

13. The Peltier effect can be
used to createa
Refrigerator that is
compact and hasno
circulatingfluid or moving
parts.Suchrefrigerators
are useful in applications
where theiradvantages
outweighthe disadvantage
of their verylow efficiency
Refrigerator

14. Dehumidifiers:
The coolingeffect of Peltier
heat pumps can be used to
extract water fromthe air
in dehumidifiers. A
camping/cartype electric
cooler can typicallyreduce
the temperature by up to 20
°C (36 °F) belowthe
ambient temperature.
Climate-controlledjackets
are beginningto use Peltier
elements.

15. The effect is usedin satellite
and spacecraft to counter
the effect of direct sunlight
on one side of a craft by
dissipatingthe heat over
the coldshaded side,
whereuponthe heat is
dissipated by thermal
radiation into space.
satellite

16. In fiber optic applications,
where the wavelengthof a
laser or a component is
highlydependent on
temperature, Peltiercoolers
are used alongwitha
thermistor in a feedback
loop to maintaina constant
temperature and thereby
stabilize the wavelengthof
the device.
fiber opticapplications

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