Improvement of Microwave Heating Uniformity Using Symmetrical Stirring

This study proposes a new method of symmetrical stirring using an anchor paddle to improve the heating uniformity of liquids. To simulate the complex physical process of microwave heating a fluid while stirring it, the finite element method (FEM) and the arbitrary Lagrangian–Eulerian (ALE) method were utilised to model the interactions between electromagnetics, heat transfer, and fluid flow. The temperature coefficient of variation (COV) of the water when subjected to microwave heating and the symmetrical stirring paddle decreased by an 11.2–81.5% compared to that achieved by the traditional rotating turntable method, and it further decreased as the stirring frequency increased. This implies that the stirring method performed more favourably than the rotation method in improving the uniformity of the microwave heating. The distributions of the three physical fields indicated that symmetrical stirring enhanced the axial fluid flow and heat transfer, reducing the large intrinsic temperature difference along the vertical direction. Furthermore, the computation results were validated experimentally, showing that the proposed method is sufficiently accurate for evaluating the uniformity of microwave heating.