Dehydrating is one of the most common processes in industry. This process is implemented by various techniques, such as freeze-drying. It is an energy-consuming process. Microwave sources are a good choice to supply the energy needed for this process. In reality, it is microwave-assisted freeze-drying. The microwave sources can be delivered around a few kilowatts. Electromagnetic energy is converted into thermal energy due to the interaction of electromagnetic fields and materials. In addition to providing energy, the microwave-assisted freeze-drying is time-saving. This method is fast due to penetrating electromagnetic fields in the material. It results in volumetrically heating instead of heating from the surface of the material in conventional methods. Usually, the frequency of electromagnetic fields is 2450 MHz, which is allocated by regulatory commissions in dielectric heating methods. In the following, the mechanism of this method is described. All relations governing the transfer of mass and heat are mentioned. How to transfer and dissipate energy is described. Dielectric properties of different materials are listed. The effective parameters in determining dielectric properties are discussed.
The existence of metasurface, in the way of propagating wave, affects the wave by blocking some of the incident power. In this chapter, modal analysis is used to analyze a metasurface structure, which is a two-dimensional periodic structure. First, the structure is modeled by an element inside the TEM waveguide. In the following, the reflected and transmitted waves are expanded by different modes, potentially propagated along the TEM waveguide. The key parameters in determining the behavior of structure are specified. The effect of each parameter in behavior of the structure is shown. This technique is used for different metasurfaces, and simulation results are presented in the chapter. This technique is extended to multilayer metamaterial structures.
Part of the book: Metamaterials and Metasurfaces