Industrial microwave ovens are widely used in agri-food and chemical applications. Resonant cavities are used to speed up chemical reactions and have the advantage to be small sized and efficient in terms of microwave distribution. These multimode cavities are considered as batch ovens where a small amount of products is treated. Rotating plates are added in the cavities to ensure a homogeneous power distribution. For continuous treatments, microwave tunnels can be used. In these ovens the microwave distribution is supposed to be homogeneous. Due to the difficulty to measure the electromagnetic field, this assumption is difficult to prove in the case of industrial plants. The aim of this study is to simulate the behavior of the electric field inside a microwave applicator with conveyor belt system using Comsol 3.5a. The numerical results are discussed and experimental validations (from a qualitative point of view) are presented. Keywords: microwaves, finite elements, heat transfer

1. Introduction

Applicators with conveyor belt systems can be used in industry for multiple applications. Microwave applicators with conveyor belt systems are rapidly spreading due to the speed of the process and its efficiency [Metaxas & Meredith, 1986]. Conveyor belt carries load through the input and output ports of the industrial applicator. To improve thermal treatments, it is necessary to understand the different phenomena that occur inside the applicator. In case of microwave conveyors, it is difficult to predict the behavior of electric field inside the treatment zone. Thus, a numerical study is well suited to calculate electric field inside and predict its effect on loads. Many numerical techniques have been used to model microwave heating applicators with different loads. These methods include finite differences, finite elements, transmission line methods and others [Dibben D.C and Metaxas, 1994, 1997; Al-Rizzon et al, 2005; Dominguez-Tortajada et al, 2005; Yakovlev, 2006; Hallac, A and Metaxas, A.C, 2006]. This paper presents a numerical study of the electric field in an industrial microwave conveyor belt and its effect on load using COMSOL® code with qualitative experimental validation.