Study Of Electrically Conductive Bead On Microwave Drying Uniformity

Compared to traditional drying methods, microwave drying has many advantages such as fast-drying, easy to control and no pollution. Therefore, microwave drying is widely applied in food industry. However, non-uniformity of microwave drying is a major bottleneck in microwave drying practice because of low product quality at present.During the process of microwave heating, the temperature profiles inside the material are very complex, depending on the electromagnetic field intensity in the material, dielectric properties, moisture content distribution inside the material, etc. And these parameters are interplayed, so how to resolve the non-uniformity of microwave heating is a difficult problem.Aiming at non-uniformity of microwave drying, it is illustrated that placing electrically conductive beads in cavity can improve uniformity, also studied improvement of microwave drying uniformity using settling and random moving beads. To make absorption of microwave more even, we place beads to improve uniformity of electric field distribution. Electrically conductive beads with metal material can reflect microwave power from stronger electric field intensity district to weaker district because microwave can be reflected on metal.It is researched that the effect of settling an electrically conductive bead on improving partial overheating phenomenon in microwave food heating, depending on studying the electrical distribution in microwave cavity and temperature distribution in material, The results show that placing a settling bead in cavity can change electrical distribution in cavity, weaken electric field intensity concentration, improve the uniformity of electric field distribution and temperature in material and enhance quality of product. Also, placing a bead on the positions which are close to corners and the distance between it and material surface is about half a wavelength can weaken the partial hot spot phenomenon efficiently.In addition, it is studied that the effect of random moving electrically conductive beads on improving the electric field distribution in microwave rotary dryer. On the basis of DEM, It is simulated to research random mixture of soybean and beads by EDEM(?) software, and study the effect of microwave feed inlets and beads on electric field distribution by COMSOL Multiphysics(?). The results show that in rotary dryer,4symmetrical, stagger, different-orientation microwave feed inlets can improve electric field distribution uniformity; random moving beads can increase electric field intensity, speed up drying rate.