A comprehensive mathematical model of heat and moisture transfer for wood convective drying
A comprehensive mathematical model of heat and moisture transfer for wood convective drying
复制标题
木材对流干燥热湿传递综合数学模型
DOI：
10.1515/hf-2016-0148
复制
发表时间：
2017
期刊：
影响因子：
2.4
通讯作者：
Y. Cai
中科院分区：
文献类型：
--
作者：
Jingyao Zhao;Y. Cai
摘要本研究的重点是开发一种特定的干燥模型，用于设计和运行干燥室中堆叠木材的干燥系统。也就是说，建立了一个综合的三维（3D）数学模型，描述了木材在考虑周围流体流动影响的情况下进行对流干燥。在开发模型时，木材和流体流动的特性，即速度、压力、温度、相对湿度（RH）和含水率（MC）由质量、动量和能量守恒方程以及热力学关系来描述。利用商业软件COMSOL Multiphysics对模型进行了数值求解。在实验室条件下，仿真结果与实验数据进行了对比验证。在干燥过程中，气流循环是不均匀的，这是造成木材温度和MC变化速率不同的原因。在干燥初期，这种差异较大，但随着干燥过程的进行，这种差异逐渐减小。同时，观察了室内堆积木材周围的瞬态湿度聚集现象，以响应气流循环和水分蒸发速率。最后，对数值计算和实际检测中产生的误差来源进行了识别和讨论。
Abstract The focus of this study is the development of a specific drying model for the design and operation of drying systems for stacked lumber in drying chambers. Namely, a comprehensive three-dimensional (3D) mathematical model of heat and moisture transfer in stacked wood has been developed, where the wood was subjected to convective drying that accounts for the effect of the surrounding fluid flow. In developing the model, the characteristics of wood and fluid flow, i.e. velocity, pressure, temperature, relative humidity (RH) and moisture content (MC) are described by the conservation equations of mass, momentum and energy as well as thermodynamic relations. The model presented was solved numerically by means of the commercial software COMSOL Multiphysics. The simulation results were validated against experimental data under laboratory conditions. Air current circulation was found to be non-uniform during drying, which accounts for the different rates of temperature and MC in wood. At the initial stage of drying, this difference was relatively large but reduced gradually with the drying process. Meanwhile, the transient gathered phenomenon related to humidity around the stacked wood in the chamber was observed in response to air current circulation and evaporation rate of moisture. Finally, sources of error incurred in numerical calculations and actual detection were identified and discussed.