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《Journal of Forestry Engineering》 2018-01
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Heat and mass transfer multi-scale unit characterization model in the drying process of Pinus sylvestris

LIU Jijian;YU Jianfang;WANG Ximing;LI Yaling;Hebei Saihanba Machinery Forest Farm;College of Material Science and Art Design,Inner Mongolia Agricultural University;  
Understanding the theory of heat and mass transfer in wood drying is conducive to wood drying process improvement and energy saving. Pinus sylvestr was used as experimental material and a multiscale mathematical model was construct,which can accurately simulate the temperature and moisture content changes during the wood drying process. The model was made up of three coupled equations: two water diffusion equations and one energy balance equation in macroscopic level,and water transfer balance in single cell equation in microscopic level. The process of parsing the model was as follows: analyzing of the initial and boundary conditions,forming of the finite element mesh,the discretization of the equation,searching the corresponding parameters,and solving the programme by MATLAB software. Finally,the accuracy of the established multi-scale model was verified by the experimental analysis. The results showed that:( 1) Comparing the experimental value and analog value by slice weighing method and density volumetric method at 80℃,the P value of slice weighing method was lower than 0. 5,while the P value of density volumetric method was higher than 0.5,proving that the density volumetric method was more coincident with model method than slice weighing method was;( 2) The average moisture content of sawn timber change experiment was performed by the density volumetric method at 40℃,60℃ and 80℃,experiment and model results were congruence. The multi-scale model could reflect the heat and mass transfer behavior at the wood drying process. Establishing the heat and mass transfer mathematical model from different scales can accurately reflect the moisture content changes in the wood and spatial distribution.
【Fund】: 科技部国际合作项目(2013DFA32000);; 内蒙古自治区自然科学基金(2015MS0344);; 内蒙古自治区高等学校科学研究项目(NJZY11054);; 博士科研启动基金(BJ10-25)
【CateGory Index】: S781.71
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