thermocouple,peltier effect,seabeck effect

gives information about heat and thermodynamics

1. Group member Name Roll no Maryam 15261509-022 Sundas 15261509-009 Iqra 15261509-018 Saira 15261509-005 Samra 15261509-035

2. Content: Low Temperature physics Thermo Electricity Thermo couple Thermo seabeck’s effect Peltier’s effect

3. Low Temperature Physics

4. Temperature: A measure of the warmth or coldness of an object or substance with reference to some standard value. The temperature of two systems is the same when the systems are in thermal equilibrium. www.dictionary.com/browse/temperature

5. Thermodynamics by Prof.M.H.Musaddiq low temperature : In every day life, temperature below or around 0 °C are termed as low temperatures. The branch of physics which deals with production of low temperature is called cryogenics or low temperature physics.

6. www.comsol.com/multiphysics/joule-thomson-effect Joule thomsan effect: For several years, James Prescott Joule and William Thomson – both British physicists – worked in collaboration, conducting experiments designed to analyze and advance thermodynamics. In 1852, the researchers made a particularly notable discovery. They found that a temperature change can occur in a gas as a result of a sudden pressure change over a valve. Known as the  Joule-Thomson effect  (or sometimes the  Thomson-Joule effect

7. James Prescott Joule

8. William Thomson

9. Samra 2.Thermo Electricity by

10. CONTENTS : 1: Introduction 2: Why Thermoelectricity? 3: Principle 4: Working and Construction 5: Material of choice for TEG 6: Advantages and Disadvantages 7: Applications 8: Conclusion

11. INTRODUCTION: Thermoelectric power generation using waste heat energy as an alternative green technology..

12. Why thermoelectricity? Increasing energy demand.. Increasing pollution.. Increasing IC heat.. Green energy production by thermoelectricity. Automobile waste heat thermoelectric power generation. On chip thermoelectric cooling.

13. How does thermoelectricity work? In 1821, Thomas Johann SeeBeck discovered that a thermal gradient formed between two dissimilar conductors can produce electricity. At the heart of the  thermoelectric effect is the fact that a temperature gradient in a conducting material results in heat flow; this results in the diffusion of charge carriers.

14. WORKING:

15. Material of choice for thermoelectricity: TE Parameters Materials.. Semiconductors most suitable TE material. Allow separate control of G (electrons) and κ (phonons)

16. Choice of material:

17. advantages and disadvantages: ADVANTAGES  Environmentally friendly  Recycles wasted heat energy  Reliable source of energy  Lowers production cost  

18. DISADVANTAGES: TE material is expensive. Structural failure of TE element at high temperatures. Electrical resistivity increases.

19. CONCLUSION:  Thus, by using Teg, the waste heat can be used to generate electricity.  Simulations and experiments has been conducted and more efficient systems can be developed in future with Nanocrystalline approach. 

20. Iqra 3.Thermo couple

21. Thermocouple:- Thermocouple is a combination of two words: Thermo : relating to heat. Couple: a pair of forces.

22. What is a Thermocouple? A thermocouple is a temperature measuring device consisting of two dissimilar wires forming electrical junctions at different temperatures . A thermocouple produces a temperature-dependent voltage as a result of the thermoelectric effect, and this voltage can be interpreted to measure temperature. Thermocouples are a widely used type of temperature sensor . Zemansky -Heat And Thermodynamics

23. Thermocouple wires:-

24. How does a thermocouple work ? When two wires composed of dissimilar metals are welded at both ends , creating a junction and the junction is heated. This junction is where the temperature is measured. When the junction experiences a change in temperature, a voltage is created. Which means that when the junction of the two metals is heated, or cooled, a voltage is produced. http://www.thermocoupleinfo.com/

25. Thermocouple types:- Thermocouples are available in different combinations of metals or calibrations: “Base Metal ” “Noble Metal” Type J Type R Type K Type S Type T Type B Type E Type C http://www.thermocoupleinfo.com/

26. Applications:- Steel industry. Temperature sensor for measurement . Control and convert temperature in electricity . In stoves & tosters . Used in researches. Used in offices. Used in homes . Temperature measurement for furances . https://www.slideshare.net/ShyamakantSharan/ppt-thermocouple

27. Working Principle:- The working principle of the thermocouple is based on two effects discovered by: Seebeck effect Peltier effect They are as follows: https://www.slideshare.net/keshavakrishnan34/thermocouple-52341426

28. Sundas 4.Seebeck effect by

29. History In 1821, Seebeck found that: A current flows in a circuit consisting of two dissimilar metals, when one junction is heated, while other junction is kept cold .

30. Seebeck effect The existence of a thermal emf € AB in the circuit is known as the Seebeck effect . In figure, a thermocouple consisting of two different conductors A and B has its junctions in contact with different heat reservoirs. We call the warmer junction at T the test junction, and the other at temperature T R the reference junction. Zemansky-HeatAndThermodynamics

31. Zemansky-HeatAndThermodynamics

32. Conti … When the temperature of the reference junction is kept constant, the thermal emf is found to be a function of the temperature T of the test junction. This fact enables the thermocouple to be used as a thermometer. Zemansky-HeatAndThermodynamics

33. Conti … The Seebeck effect arises from the fact that the density of charge carries (electrons in a metal) differs from one conductor to another and depends on the temperature. When two different conductors are connected to form two junctions and two junctions are maintained at different temperatures. Zemansky-HeatAndThermodynamics

34. Conti … For a given T R , € AB is a function of T. If T R is changed to another constant value, the relation between € AB and T is the same expect for an additive constant. Zemansky-HeatAndThermodynamics

35. Conti … It follows therefore that the value of d€ AB / dT is independent of T R and depends only the nature of A and B and upon T. The derivative d€ AB / dt , at any value of T R , is known as the thermoelectric power of the thermocouple. Zemansky-HeatAndThermodynamics

36. Peltier effect In 1834, a French watchmaker and part time physicist, Jean Peltier found that an electrical current would produce a temperature gradient at the junction of two dissimilar metals when the current direction was r reversed, the cold junction w would get hot while the hot junction w would get cold.

37. Cause of peltier effect When a current flows across the junction of two metals, it gives rise to an absorption or liberation of heat, depending on the direction of the current. i.e. Applying a current (e - carriers) transports heat from the warmer junction to the cooler junction.

38. Example As an example of the Peltier effect, consider the circuit shown here. Under these conditions, it is observed, as indicated in the diagram, that the right-hand junction is heated. It shows, in other words, that electrical energy is being transformed into heat energy. Meanwhile, heat energy is transformed into electrical energy at the left junction, thereby causing it to be cooled. When the current is reversed, heat is absorbed at the right junction and produced at the left one.

39. Conti. The rate of evolution of or absorption of heat is proportional to the current &thus the peltier effect is reversible. If direction of current is changed then the peltier effect is also reversed. The energy absorbed or evolved at one of the junctions of the two dissimilar metals when one ampere of current flows for one second is called Peltier coefficient ,denoted by ∏

40. Experimental demonstration of peltier effect In this experiment, two rods of bismuth and antimony are joined as shown. A differential air thermometer is placed with its two bulbs at junctions A and B.

41. Conti.. When no current flows through the thermocouple , the junctions A & B are at same temperature. When large current is passed through the thermocouple , then there will be: Evolution of heat at junction A. Absorption of heat at junction B. Hg pellet moves to one direction If direction of current is changed the pellet moves in the opp. Direction indicating that now A has become cold and B has become hot.