纸张干燥中湿分扩散系数的估算

Estimation of moist diffusion coefficient in paper drying

纸张干燥过程涉及到多孔介质的热质传递,如何确定质量扩散系数是所建立的多孔物料湿分扩散模型能否进行数值计算的关键。按Liukov公式将湿分扩散系数视为含湿质量分数的非线性函数,在恒温下进行纸张干燥实验,通过比较湿分蒸发质量的测量值与理论计算值,采用多变量寻优的方法对多孔介质一维情况下的湿分扩散系数进行估算,得到了实验条件下的纸张湿分扩散系数的计算公式。并进一步确定了纸张中的湿分扩散系数与含湿质量分数和温度之间的函数关系式。

Paper drying involves heat and mass transfer in porous media. How to precisely determine the moist diffusion coefficient is very important when the moist transfer theoretical models of porous media are numerically calculated. Paper drying test was done under isothermal conditions. The moisture diffusion coefficient is a non- linear function of the moisture mass fraction as described by Liukov. One method of parameter estimation for porous media at one-dimension involving moisture transfer in paper drying process was presented by adopting muhivariable optimization method and comparing calculated moisture evaporation amount with measured ones. The calculation equation of moist diffusion coefficient under experimental condition was found. The relation between moisture diffusion coefficient, moisture mass fraction and temperature in paper sheets was also determined.