木材微波-真空干燥特性的研究.doc

木材微波-真空干燥特性的研究 （作者：李贤军，导师：张璧光教授FSP上时，木材中的自由水和水蒸汽在压力梯度的作用下以渗透流的形式在木材内部迁移，迁移的强度主要取决于微波辐射强度和木材初含水率；当木材含水率在FSP以下时，木材中的吸着水本身不产生移动，而是向邻近的细胞腔蒸发，再在压力梯度的作用下，以水蒸汽的形式向木材表面迁移；在微波-真空干燥过程中，因热扩散、毛细张力、含水率梯度引起的水分迁移可以忽略不计。④ 基于微波-真空干燥过程中木材内部的热、质迁移机理，以压力梯度为木材内水分迁移的驱动力，从能量和质量守恒方程出发，建立了微波-真空干燥过程中，木材内热、质迁移的一维数学模型。模拟结果亦证明木材的整个微波-真空干燥过程可以分为快速升温加速干燥段、恒温恒速干燥段和后期升温减速干燥段。实验证实用该模型对木材的微波-真空干燥过程进行模拟是可行的，且具有较高的模拟精度。其模拟含水率数据与验证实验数据的相关程度较高，相关系数的平方为0.99；模拟温度数据与实验测定温度的相关程度略低，但其相关系数的平方也在0.98以上。 关键词： 木材干燥 微波-真空 热、质迁移 数学模型 Research on the Characteristics of Wood Microwave-Vacuum Drying （Li Xianjun Directed by Prof. Zhang Biguang）Wood drying is not only the most energy intensive and time consuming component of the lumber manufacturing process, and which is also a key factor to affect the quality of wood product. It is impossible for conventional hot air drying technology to solve the drying problem of plantation hard wood and wood with large dimension. Microwave-vacuum (MV) drying is a new potential drying technology with high drying rate even at low temperature. The paper related to the fundamental law and mechanism of wood drying under microwave-vacuum was seldom published. In this paper, under the condition of MV, the drying characters of wood using Masson pine as experimental material has been systematically researched and concluded, the mechanism of heat and mass transfer in wood has been described, and the mathematic model based on the theory of heat and mass transfer has been developed to model the drying process of wood during MV drying. The research will provide a theory basis for the further application of MV drying technology in wood industry. The main conclusion and originality can be showed as the following: 1. The drying characters of wood under MV has been systematically analyzed and concluded based on a lot of experiences. The results show :①.The average drying rate of wood increases with the increase of microwave input power, wood initial moisture content and vacuum level;②.T