Simulation And Optimization Of Efficiency And Uniformity Of Cylindrical Microwave Heater

Microwave heating, which has some unique advantages such as fast, efficient and selective heating, is widely used in industrial production, agricultural production and livelihood. However, when different heating objects are heated in the microwave heating chamber, it will form different electromagnetic field distribution, and then it has different heating efficiency and uniformity. To improve the efficiency and uniformity of microwave heating, it is necessary for us to make a study for the rule how different heating objects form different electromagnetic field distribution in the microwave heating chamber. Based on the HFSS electromagnetic simulation software, this paper analyzed a cylindrical microwave heater’s efficiency and uniformity when it heat different loading medium. The main work is summarized as follows:This paper analyses and summarizes the basic theories for the design of microwave heating chamber which include Finite Element Method theory, Resonate Cavity theory, Perturbation theory and the application of HFSS software in the microwave reaction cavity design.This experiment uses HFSS electromagnetic simulation software to simulate cylindrical microwave heating chamber’s design parameters including the position and length of feed port, the radius and height of inner cylinder, the load type and size, and the influence of these design parameters on the heater’s efficiency. The results show that the efficiency of cylindrical microwave heating applicator are affected by various design parameters:(1) When the angle between the two feed ports is greater than120?, there is low echo in the feed ports, and most of the microwave energy are absorbed by the heated object, so heating efficiency is relatively high;(2) when the feed’s length is greater than30 mm, its influence on the heating efficiency is stable; when the feed’s length is between 80 mm and 90 mm, the heating efficiency is slightly higher;(3) when the cylinder radius and height differ between 200 mm to 250 mm, the heating efficiency is the highest;(4) when the thickness of load medium are even number times of its effective electromagnetic wavelength, heating efficiency is the highest. The simulating results show that the heating efficiency of the optimized cylindrical microwave heating chamber is improved to 99%.Based on the HFSS and heating uniformity evaluation method, this paper studies the influence of the number of feed ports and the heating chamber’s inner cylinder that has concave cambered surface structure on the heating uniformity of cylindrical microwave heating chamber. Results show that when a cylindrical heating chamber’s inner cylinder has concave cambered surface structure, it can scatter electromagnetic waves to multiple directions, and urge electromagnetic energy experience more times of reflection in the heating chamber, so it can gain more evenly electromagnetic field distribution in the heating chamber, and then improve effectively the uniformity of microwave heating. When it keeps it original heating efficiency, comparing with smooth inner cylinder structure, the inner cylinder that has concave surface structure can improve the heating uniformity overall 10.7%, and the highest improvement of the surface’s electric field distribution uniformity can be up to 25.8%.