@T SHANMUKHA REDDYON 22/03/17

SEEBECK PELTIERWILLIAM THOMSON

Contents

1. Seebeck effect

2. Peltier effect

3. Joule Thomson effect

4. Thermo-electric effect

5. Thermo-electric generators

• The Seebeck effect is a phenomenon in which atemperature difference between two dissimilarelectrical conductors or semiconductors produces avoltage difference between the two substances.

• This was discovered by German physicist ThomasSeebeck (1770-1831).

• When heat is applied to one of the two conductors orsemiconductors, heated electrons flow toward the coolerone. If the pair is connected through an electrical circuit,

direct current (DC) flows through that circuit.

• The voltages produced by Seebeck effect

are small, usually only a few micro volts

per Kelvin of temperature difference at the junction.

• Numerous devices can be connected in seriesto increase the output voltage or

• In parallel to increase the maximum

deliverable current.

Seebeck Coefficient:

• The voltage produced between the two points on a conductor when a consistent temperature difference of 1o Kelvin is maintained between them is termed as Seebeck coefficient.

• One such combination of copper constantan, has a see beck coefficient of 41 micro-volt per Kelvin at room temperature.

• The Peltier effect is a phenomenon in which temperature difference created by applying a voltage between two electrodes connected to a sample of semiconductor material.

• This was discovered by

Jean Charles Peltier.

• This phenomenon can be useful when it is necessary to transfer heat from one medium to another on a small scale.

• Peltier effect is converse of Seebeck effect.

French physicistJEAN CHARLES PELTIER

Peltier Coefficient:

• Peltier coefficient is defined as the amount of heat energy absorbed or evolved due to peltier effect at the junction of two dissimilar metals when one coulomb of charge passes through the junction.

• Peltier coefficient is denoted by π.

• Value of Peltier Coefficient is different for different thermo-couple .Its value also depends upon the temperature of the

junction.

• Thomson effect is the phenomenon in which the generation or absorption of heat in a current carrying conductor with a temperature gradient.

• A phenomenon discovered in

1854 by William Thomson,

later Lord Kelvin.LORD KELVIN

(WILLIAM THOMSON)

• Thomson showed that the Peltier heat or power (Qp) at a junction was proportional to the junction current (I) through the relationship Qp = πI,

where π is the Peltier coefficient.

Thomson coefficient:

• Through thermodynamic analysis, Thomson also showed the direct relation between the Seebeck and Peltier effects, namely that π = αT,

where T is the temperature of the junction(Thomson coefficient)

• The thermoelectric effect is the direct conversion of temperature differences to electric voltage and vice versa.

• A thermoelectric device creates voltage when there is a different temperature on each side. Conversely, when a voltage is applied to it, it creates a temperature difference.

• The term "thermoelectric effect" encompasses three separately identified effects: the Seebeck effect, Peltier effect, and Thomson effect.

Applications:

• To measure temperature using thermo electric thermometer.

• To detect heat radiation using thermopiles.

• Thermoelectric refrigerator or generator.

(A thermopile is an electronic device that converts thermal energy into electrical energy.)

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• A thermoelectric generator (TEG), also called a Seebeck generator.

• A thermo electric generator is a device which converts heat (temperature differences) directly into electrical energy through a phenomenon of thermo electric effect (Seebeck, Peltier, Thomson effects)

• Advantages

• Easy maintenance: They works electrically without any moving parts so they are virtually maintenance free.

• Environment friendly: Thermoelectric generatorsproduce no pollution. Therefore they are eco friendlygenerators.

• Compact and less weight: The overall thermoelectriccooling system is much smaller and lighter than acomparable mechanical system.

• High Reliability: Thermoelectric modules exhibit veryhigh reliability due to their solid-state construction

Applications: