PRESENTATION ON BASIC THERMOELECTRIC EFFECT ON MAGNETIC MANOSTRUCTURE

Name- Rupesh Kumar DasUID- k10741Course- B.TechBranch- MechanicalSem- 6th

Sub- Refrigeration and Air conditioning

Thermoelectric effect on magnetic nanostructure gives rise to magnetic refrigeration.

It is based on magneto caloric effect. Effect is caused due to varying magnetic entropy of

magnetic materials. It can be easily used in place of VC cycle. It has lower cost

than VC cycle and consumes less electricity.

Introduction

It is a magneto thermodynamic phenomena. Defined as the heating and cooling of magnetoelectric

material when it is magnetised and demagnetised respectively where pressure has no influence.

Entropy- It is defined as degree of randomness of the system.

Theory

Substance placed in insulated environment. Magnetic field and heat increases This causes magnetic dipoles of atoms to align. The net result is that the total entropy of the item is not

reduced and items heats up.

Adiabatic demagnetisationSubstance returns to another adiabatic stateEntropy remains constantMagnetic field is decreasedThermal energy causes magnetic moments to overcomes the

field and sample cools

Adiabatic magnetisation

No compressor No refrigerant gas Low pressure operation Low running cost Safety cooling and very less environment impact

Disadvantages Initial investment is more as compared with conventional. Magneto caloric material are rare earth material hence their

availability also adds up disadvantages .

Advantages

Conclusion The conventional gas compression refrigerators have been

mainly used for refrigeration applications. Generally, such refrigerators are not power-efficient. In addition, gases used in these refrigerators causes harmful effects on the environments. This has led to the development of magnetic refrigeration technology. Over the last decade or so, magnetic refrigeration at room temperature has become the subject of considerable attention.

This technology is based on the use of magnetocaloric effect: that is the response of a solid to an applied magnetic field which emerges as a change in its temperature. This technology is ultimately aimed at developing a standard refrigerator for home use.

References 

Allab, F. (2008). Conception et réalisation d’un dispositif de réfrigération magnétique base sur l’effet magnétocalorique et dédié a la climatisation automobile, Thèse de doctorat, Grenoble, Institut National Polytechnique de Grenoble.

  Bianchi, A.M., Fautrelle, Y., Etay, J. (2004). Transferts

thermiques, première édition, Presses polytechnique et universitaires romandes, ISBN 2-88074-496-2, Lausanne.

  Bjork, R., Bahl, C.R.H., Smith, A., Pryds, N. (2010). Review

and comparison of magnet designs for magnetic refrigeration. International. Journal of Refrigeration. 33, 437-448.