Thermodynamics In The Presence Of Electromagnetic Fields And Its Applied Research

Electromagnetic technology(ET), commonly existing in the physical world, is a integrated technolgy of wide applications and coverage. The classical electromagnetic theory laid a solid foundation for the development of the ET. After entering the 21st century, with the development of every subject, ET has a interdisciplinary study with related disciplines, which is applied to the fields of energy saving, environmental protection, mechanism, medicine, agriculture, biology, national defense and so on.The further wide applications of ET need a deep study of interactions between electromagnetic fields and material. Some of the physical mechanisms are still not clear because of the particularity and complexity of interactions between electromagntic fields and material. Therefore, the development and research of ET is still an important subject of technological workers now. This passage bases on electromagnetic field theories, analyzes the physical meanings of electromagnetic energy density from the standpoint of interactions between fields and medium. The physical mechanisms of electromagnetic energy loss in alternating electromagnetic fields are also analyzed and the expression of mean power density of electromagnetic energy loss is derived in harmonic alternating external fields.There is an apparent effect to use the electromagnetic fields strengthen physical and chemical processes and which is an effective method to use thermodynamics describe processes of the electromagnetic actions. The research of the thermodynamics is divided into the research of the equilibrium thermodynamics and nonequilibrium thermodynamics according to the state of objects of study. To the system of equilibrium thermodynamics in the electromagnetic fields, the electric parameters and magnetic parameters is added to the differential expression of thermodynamic energy by the use of energy axiom, differential expression of electric energy and magnetic energy. Then define related assisted functions, deduce corresponding differential expressions, therefore we can analyze the thermodynamic properties of the system in the electromagnetic fields.In the ordinary nonequilibrium thermodynamics, forces in the expression of entropy production are assumed to conservative forces. But to the system of nonequilibrium thermodynamics in the electromagnetic fields, the electormagntic force is not conservative. It must deduce the balance equations again when research the nonequilibrium phenomena caused by the electromagnetic fields. Entropy balance equation is deduced by balance equations and the local equilibrium assumption. Then the energy loss and phenomenological theory are analyzed based on the entropy production.The electromagnetic wave of frequency arranges from 300MHz to 300GHz is microwave, which is widely applied to wireless communications, material processing, microwave heating, strengthening the chemical processes, medical diagnosis and so on. This passage applies the research method of electromagnetic thermodynamics to two common application areas of microwave which are wood microwave drying and microwave assisted extraction.