Moisture Transfer Characteristics of Rough Rice (I)

Identification of the Dynamic Model under Consant Air Temperature

Abstract

In order to make up a model of drying and sorption of grain under changing conditions, we identified the moisture transfer models of unhulled rice and hulled rice of a single layer under constant air temperature. In the frequency characteristics of moisture transfer, we compared the experimental results with the calculated results of various kinds of assumed drying models.
1. Because the characteristic which exists between relative humidity and moisture content is nonlinear, we separated the model into two parts; the static characteristic (equilibrium moisture content curve) and the linear component depending on frequency as shown in Fig. 2. In the latter component, we considered the equilibrium moisture content of air as input and the average moistent content of grain as output, and the frequency response between them was observed with the experimental devices shown in Fig. 4.
2. The output waves observed in these experiments were described in Figs. 5, 6, and the frequency characteristics appearing in Figs. 8, 9, 10, were obtained by arranging these results versus each frequency.
3. We calculated the frequency characteristics of the various kinds of models, and compared them with the experimental results. In the spherical model without film resistance, the calculated values agreed with the gain characteristic of the experimental values except the phase shift characteristic. In the spherical model with film resistance of moisture transfer based on two-film theory, the calculated values agreed with both gain and phase shift of the experimental values.
4. From the practical point of view, moreover, a simple lumped model was recommended, and it was revealed that an agreement between the experimental and theoretical results in both gain and phase shift was obtained even in the lumped model with reasonadle parameters.