The present work studies numerically the heating of multilayer porous packed bed which is subjected to the microwave radiation with a rectangular waveguide. The multilayer porous packed bed consists of the layers of fine and coarse beds. The simulations of electromagnetic field are described by solving Maxwell’s equations with the finite difference time domain (FDTD) method. The flow fields and the temperature profiles are determined by the solutions of the Brinkman–Forchheimer extended Darcy model, energy, and Maxwell’s equations. The study aims to understand of the influences of layered configuration, layered thickness, and operating frequency on the transport processes in a multilayer porous packed bed. The results show that all parameters have significant effect on the distributions of electromagnetic field inside a waveguide, temperature profiles, and velocity fields within the multilayer porous packed bed.
This paper proposes mathematical models of the microwave heating process of dielectric materials filled in a rectangular waveguide with a resonator. A microwave system supplies a monochromatic wave in a fundamental mode (TE10 mode). A convection exchange at the upper surface of the sample is considered. The effects of resonator distance and operating frequency on distributions of electromagnetic fields inside the waveguide, temperature profile, and flow pattern within the sample are investigated. The finite-difference time-domain method is used to determine the electromagnetic field distribution in a microwave cavity by solving the transient Maxwell equations. The finite control volume method based on the SIMPLE algorithm is used to predict the heat transfer and fluid flow model. Two dielectric materials, saturated porous medium and water, are chosen to display microwave heating phenomena. The simulation results agree well with the experimental data. Based on the results obtained, the inserted resonator has a strong effect on the uniformity of temperature distributions, depending on the penetration depth of microwave. The optimum distances of the resonator depend greatly on the operating frequencies.
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