Abstract

Power loss density and electric field distributions in a box of water loaded in a stationary microwave oven with mode stirrers are simulated by COMSOL Multiphysics. For the aspect (x:y) ratio close to 1, the load exhibits the edge heating from hot spots aligning in the y axis. The power loss density is substantially modified by varying the length (x) and width (y) for the same load thickness (z). For the aspect ratio of around 2, hot spots tend to orient along the x-axis, leaving the edges as low-heating zones. Such a non-uniform power loss density on the horizontal plane is varied with the height in the load. In contrast to an elongated load, the changes are less pronounced in the case of aspect ratio close to 1. Covering four sides of the load with copper sheets improves the heating uniformity. Furthermore, the partial shielding of the bottom plane regulates the power loss density. Small circular and rectangular holes reduce the heating cross-section, whereas the largest hole results in uniform heating with a moderate power loss density. The power loss density is maximized at the optimum size determined from the simulation. These results suggest the selection for dimensions and shielding of containers to improve the power distribution for food heating, material processing, as well as microwave-assisted synthesis and extraction.