Numerical Simulation of Microwave Heating of Low Moisture Food in a 915 MHz Cavity for Dielectric Properties Estimation
Year: 2024
Type: conference-paper
Abstract: Context and objectives In the field of food processing, microwaves are ideal for pasteurisation, sterilisation, disinfection, drying and extraction of biochemical products, for example [1]. However, one of the main difficulties in using microwaves is the nonuniformity of heating, which limits their industrial use. Understanding the temperature distribution in heated food is obviously crucial to guaranteeing the quality of a food product. While knowledge of the thermophysical properties of the products is essential, it is above all the distribution of the microwave energy absorbed that will define the level of heterogeneity of the heat treatment. The amount of energy absorbed is itself influenced by the distribution of the electric field inside the microwave oven or applicator and is highly dependent on the dielectric properties of the product. Knowledge of the dielectric properties of products is therefore an essential prerequisite for any use of microwaves. They characterize the interaction of the material with electromagnetic fields. They are defined by the real and imaginary parts of the complex permittivity ε r * (ε r * = ε r ' -j•ε r '' ; j 2 = -1). The first is the dielectric constant that represents the ability of a material to store electrical energy and the second is the loss factor that expresses the conversion of electromagnetic energy as heat. Data on the dielectric properties of foods has been published by many authors over the years. However, foods are such complex materials in terms of composition and variability that it is difficult to use models or data from the literature. It is therefore generally always necessary to determine the dielectric properties of the specific product in order to obtain reliable data. The problem of low moisture content foods, such powders, is that their dielectric properties are very low. A recent study has shown the difficulty to measure dielectric properties of such materials, whatever the techniques used: open-ended coaxial probe or perturbation cavity techniques [2]. The aim of this work is to show how numerical simulation, combined with experimental measurements, can help in estimating the dielectric properties of these low-loss products.
Source: HAL
Language: English
Subfield: Electrical and Electronic Engineering
Field: Engineering
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7117398465