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稻谷籽粒內部熱濕傳遞三維適體數(shù)學模型研究
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國家自然科學基金面上項目(31471618)


Three Dimensional Body-fitted Mathematical Model of Rice Kernel in Hot Air Drying Process
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    摘要:

    針對稻谷熱風干燥過程中出現(xiàn)爆腰,而其機理又尚未明確的問題,以圖像法構建稻谷籽粒三維適體網格,TPS法測定導熱系數(shù),逆推法計算水分有效擴散系數(shù),利用COMSOL Multiphysics軟件模擬計算熱風干燥過程中稻谷籽粒內部的溫度和水分分布,并與實驗結果對比。結果表明:三維適體數(shù)學模型具有較高的精度,干燥過程中稻谷籽粒干基含水率模擬數(shù)據(jù)與實驗數(shù)據(jù)最大誤差低于8%;稻谷籽粒內部溫度和水分分布梯度沿徑向(短軸)比沿軸向(長軸)大,且水分梯度維持時間遠大于溫度梯度;沿籽粒徑向由外表面至中心1/3長度內的水分梯度較徑向其它部分的水分梯度大,與實驗觀察的爆腰由籽粒表面向內擴展相吻合。研究結果為準確預測籽粒內部的干燥應力,揭示稻谷爆腰機理提供了基礎。

    Abstract:

    Rice cracking occurring in the hot air drying of rice kernels reduced its quality and economic values. The reason for the rice cracking is due to the local drying stress of the kernel exceeds its resistance. The drying stress includes the stresses induced by temperature and water gradient, so the temperature and water gradient is basis for predicting drying stress. The purpose was to predict the heat and mass transfer process inside the rice kernel. The image processing technology was applied to construct a three-dimensional body-fitted grid for the rice kernel. The governing equations and relative boundary conditions were developed for the heat and mass transfer processes respectively. New measuring technology (TPS) was used to measure the properties of rice kernel such as the heat conduction and mass diffusion coefficient. Finally, the Comsol Multiphysics software was applied to solve the mathematical model. The simulation results were compared with the experimental data and the difference was less than 8%, indicating high model accuracy. The temperature and water distribution gradients in the rice kernel along the radial direction (short axis) were larger than those along the axial direction (long axis), and the duration time of water gradient existence was longer than temperature gradient existence. The moisture gradient in the radial direction from the outer surface to the one-third of center was larger than that in other parts of the radial direction, which was consistent with the cracking phenomena observed in experiments—the crack extended from the surface inward. The image processing technology was applied to construct three-dimensional body-fitted grid for the rice kernel. New measuring technology (TPS) was used to measure the properties of rice kernel.

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吳中華,李凱,高敏,趙麗娟,張忠杰.稻谷籽粒內部熱濕傳遞三維適體數(shù)學模型研究[J].農業(yè)機械學報,2018,49(1):329-334. WU Zhonghua, LI Kai, GAO Min, ZHAO Lijuan, ZHANG Zhongjie. Three Dimensional Body-fitted Mathematical Model of Rice Kernel in Hot Air Drying Process[J]. Transactions of the Chinese Society for Agricultural Machinery,2018,49(1):329-334.

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  • 收稿日期:2017-05-04
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  • 在線發(fā)布日期: 2018-01-10
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