A Numerical Study of the Influence of Rotational Speed on Microwave Heating Processes in Rotating Centella Asiatica Porous Domains Using a Moving Mesh Technique

Abstract

This research investigates the influence of the rotational speed of Centella asiatica (CA) domains on the temperature distribution under microwave heating processes using a three-dimensional model. The model consists of a rectangular cavity, rectangular waveguides, and CA domains. The CA domains are constructed as six vertically stacked equidistant cylindrical domains. They are porous media consisting of a solid phase (CA) and a fluid phase (air) filled in the interstitial spaces between the solid. The moving mesh technique is used to rotate the CA domains during the simulation. The mathematical models used to describe the related phenomena consist of electromagnetic wave propagation analysis based on Maxwell's equations, heat transfer analysis based on porous media theory with the local thermal non-equilibrium (LTNE) model coupled with fluid flow analysis based on Brinkman's equations. The results illustrate the temperature distributions of the solid phase of CA domains during microwave heating, including five cases, with no rotation, and with rotational speeds of 1, 2, 6 and 20 rpm. The temperature profiles in cases with different rotational speeds exhibit similar characteristics. The temperature distribution of CA domains changes with radial distance only. Thus, the high-temperature distributions occur on the side of CA domains and low-temperature distributions occur at their centers. The highest maximum temperature, 123.27 °C, occurs with a rotational speed at 1 rpm and the lowest maximum temperature, 114.09 °C, occurs at 20 rpm. The temperature distribution in a case with no rotation is also investigated. A much higher temperature is observed, 550.02 °C. Therefore, rotation of the CA domains during microwave heating is crucial and necessary to obtain a consistent temperature distribution and prevent patchy high temperature areas in microwave applications.