Ekologiczne chłodziarki magnetyczne

Artykuł opisuje cykl przemiany energii w materiałach magnetokalorycznych, prototypy wybranych konstrukcji układów chłodzących, ich wady i zalety. Przedstawiono również tło polityczne i warunki środowiskowe wymagane przez UE w stosunku do urządzeń chłodniczych i klimatyzacyjnych.

The magnetocaloric effect (MCE) is a thermodynamic process in which the temperature changes of a paramagnetic material are the effect of an external magnetic field changing in cycles. The refrigeration occurs in two stages: the first one is the isothermal magnetizing of the material, during which the intensity of the magnetic field rises from H0 to H3 (Fig. 1 process 1-2); during the magnetizing the dipoles of the paramagnetic material become arranged parallely to the intensity of the external magnetic field and the entropy of the material decreases from S1 to S2. As a result of magnetizing, heat is transferred to the surroundings in a quantity proportional to the work executed by the magnetic field. The second stage is the adiabatic demagnetization of the paramagnetic material to the value of the field intensity of H0, during which there occures a decrease in temperature of the material from Tp to T12 (Fig. 2 process 2-3).