木材干燥预热过程的水分流和热流分析

THEORETICAL ANALYSIS ON THE MOISTURE FLUX AND HEAT FLUX IN PROCESSES OF WOOD PRE HEATING

本文将非平衡态热力学的水分流和热流线性耦合方程应用于多孔介质 (木材 )的干燥预热过程 ,从机理上分析了其水分流和热流的特性 ,同时运用在预热样品边界上积分的方法求解耦合流方程 ,针对木材干燥预热过程进行了具体计算 ,所得的有关结论与以往的实验结论相吻合。这一结果表明线性流耦合方程是研究多孔介质干燥过程中水分流和热流的特性及其相互作用规律的有效方法 ,既可揭示耦合过程中流的本质又可对其进行定量描述。因Soret效应预热过程中存在着进入木材内的水分热扩散流 ,预热结束后木材含水率将有所增加 ,而水分和热量的输运主要集中在预热开始的前 2h内。本文关于木材干燥预热的一些结果 。

The nature of moisture flux and heat flux in wood pre\|heating is analyzed by means of coupled flux equations,which are derived from the linear theories of non\|equilibrium thermodynamics.The coupled flux equation is solved by integrating on the boundary of the wood sample and the moisture change in the sample is work out.The calculation is in agreement with the previous results from experiment.It shows that the coupled flux equations are effective on analyzing the coupling between the heat flux and moisture flux.They can both depict the heat flux and moisture flux qualitatively and also estimate the magnitude of flux quantiatively.Because the temperature inside wood sample is lower than that of pre\|heating,moisture thermal diffusion occurs due to the Soret effect and the moisture of wood sample will increase to some degree in the pre\|heating process.During that period,the moisture and energy transported into wood amount to almost all of both total magnitudes within two hours.The conclusions for wood pre\|heating obtained in this paper can be used in the wood drying techniques and are useful to practical production.