木材微波真空干燥过程的数学模拟

Mathematical modeling of wood microwave-vacuum drying

该研究根据微波真空干燥过程中木材内部水分和热量的迁移机理,建立了木材微波真空干燥的数学模型,并通过试验对该模型进行了验证。结果表明:木材的微波真空干燥过程可以分为3个阶段,即快速升温加速干燥段(Ⅰ)、恒温恒速干燥段(Ⅱ)和后期升温减速干燥段(Ⅲ),且恒温恒速干燥段在整个干燥过程中所占的比例较大;该模型能较好地模拟木材在微波真空干燥过程中的温度和含水率的变化规律,其模拟精度较高,模拟值与试验值之间相关系数的平方在0.9以上,且含水率变化规律的模拟精度高于温度变化规律的模拟精度。

Based on the mechanism of moisture and heat transfer in wood during microwave-vacuum drying （MVD）, an one-dimensional mathematical model to describe the process of wood MVD was established and verified by experiments in this research. The results showed that the process of wood MVD experienced three distinct periods： Rapid warming-up with accelerating drying period （ Ⅰ ）, a constant temperature and constant rate drying period （ Ⅱ ）, and a heating-up with falling rate drying period （ Ⅲ ） . Compared with conventional hot air drying, the second period made up the bulk of the whole drying process. The predicted temperature and moisture content in wood match well with the experimental data, the square of the relevant coefficient of the values of simulation and test is above 0.9, and the simulation precision of the changing rule of the moisture is higher than that of the temperature.