Microwave characterization and mathematical simulation of dielectric properties in poplar wood with different moisture contents

Abstract

In recent years, there has been a marked increase in demand for timber. Conventional timber drying methods, characterized by long drying times and significant pollution, have struggled to meet this demand effectively. In contrast, microwave drying, as an emerging technology, offers the benefits of speed, high efficiency, environmental friendliness, safety, and sterilization capabilities. However, this method also faces challenges such as uneven drying and low efficiency during the process. To address these issues, the article initially explores the theoretical relationship between the dielectric permittivity, moisture content, energy utilization rate, and microwave penetration depth. It then delves into the principles of microwave heating and outlines the main factors influencing timber drying, specifically moisture content and microwave frequency. Subsequently, a three-port circular resonant cavity was designed using finite element analysis software using a homogeneous wood material as a simulation object in order to simulate the effect of microwave application on the uniformity of the internal temperature distribution during the drying process. The simulation analyses and fits the relationship between moisture content, dielectric permittivity, energy utilization rate, temperature coefficient of variation, and microwave penetration depth, culminating in a model of high predictive accuracy. Simulated results confirm that the methods and parameter settings proposed in this paper are highly effective, offering potential solutions to the challenges of uneven temperature distribution and low energy utilization rates in microwave timber drying.