An Application of Thin-Layer-Drying Theory to Predicting Grain Moisture and Temperature Changes in a Mixing Bed of Rough Rice

The rough-rice-drying process in a mixing type dryer was analysed by the theory of thin layer drying. The drying period of rough rice in the dryer is assumed to be a pre-heating period, and a heat balance equation is introduced as one of the basic equations. The Becker\u27s equation of moisture content, the Henderson\u27s equation of equilibrium moisture content, and the equations of air and vapour characteristics are used for the analysis with a slight modification. The drying process in mixing type dryer is assumed to be as folloes; 1） Drying air increase its humidity and reduces its temperature by absorbing the moisture of the products through the mixing layer from the inlet to the outlet. This means that the state of air changes with drying time and grain position as in deep stationary bed. 2) The state of grains is independent of their position, but dependent on drying time. This is due to constant mixing. 3) The drying rate of grains, averaged by constant mixing, is independent of their position although the local drying rate varies with their position. 4） The heating rate of grains is also independent of their position. This is the same situation as in the drying rate. The equations on the misture content, the temperature of grains, the absolute humidity, and the enthalpy of drying air are being derived. The numerical method of solving these equations is given together with its computer program. Results computed with this theory agree well with the measured values with the practical apparatus, L. S. U. type dryer.現在我が国の大規模乾燥施設に採用されている籾の混合乾燥について,数学的モデルを与えて理論と計算法を導いた.その具体的計算の基礎は最近大きな発展が見られる薄展理論で,これに多くの考察を加え,それを基に種々のデータを計算機の利用に都合のよいように式の形を整理した.これらの成果を利用し,混合乾燥機の調査データを解析した結果,大体の一致を見ることができた