A coupled electromagnetic and heat transfer model for casket designing for efficient microwave heating: An insight from theoretical analysis, Multiphysics simulation, and experimental investigations

Abstract

Microwave heating is extensively used in several industries due to its advantageous capabilities such as volumetric heating, reduced processing time and less energy consumption as compared to conventional heating. Refractory casket insulation is primarily used in microwave heating systems for the purposes of insulation and effective microwave transmission. This investigation aims to provide knowledge and insights for selecting suitable high-temperature refractory insulating casket materials, particularly focusing on three different types: dense alumina, dense alumina-silica, and porous alumina-silica casket. The investigation involves evaluating the microwave transmission efficiency (PTC) and insulation resistance capability of the three casket materials concerning their dielectric and thermophysical properties at varying temperatures. Among three casket materials, porous alumina-silica casket showed a significantly lower values of dielectric constant (1.50 to 1.68), loss tangent (0.000086–0.00318) and thermal conductivity (0.26 W/m·K to 0.50 W/m·K) over the entire temperature range. Consequently, the porous alumina-silica casket exhibited superior insulation and PTC (0.9997 to 0.9876) during microwave heating. The heating phenomenon of each casket material has been established. The COMSOL Multiphysics model was used to analyze the microwave heating behavior of SiC susceptor with varying casket composition and geometry under similar parameters for the first time. A higher heating rate was observed by COMSOL simulation for the porous alumina-silica (58.8 °C/ min) casket than dense alumina-silica (22.31 °C/ min) and dense alumina (9.63 °C/min) casket during microwave heating of SiC susceptor at 1200 W, 1500 s. The COMSOL simulation data were corroborated with experimental results. The study serves a general guideline to select an appropriate casket material for any microwave processing.