The Application of Forced Air Drying Theory to the Deep Bed Drying of Rough Rice (II)

Abstract

The drying characteristics curves of a single paddy grain including a large drying rate of early drying period were represented by two drying period of Fig. 1 namely period I (a-b) and period II (b-o).
In this paper the forced air drying theory was combined with the above drying characteristics and the new drying equations were presented.
The results obtained were as follows.
1) The drying contant and equilibrium moisture content for period I were give in Eqs. (24) and (27) where K_I′ was the modified drying constant for period I.
2) The second critical moisture content M_k between period I and II was given in Eqs. (26), (28) and Fig. 4.
3) The drying process of bulk was divided in period I, mixed period and period II as in Fig. 2.
The Eqs. (10)-(13) were for determination of moisture content and drying rate of bulk for period I.
The mixed period was the period between τ₁′ (eq. (14) and τ₂ (eq. (16)).
Bed depth ζ_k of zone II was obtained from Eq. (17) and the bed depth of zone I was ζ_L-ζ_k.
The moisture content and drying rate of bulk for mixed period were calculated by Eqs. (20) and (21).
The moisture content and drying rate of bulk for period II were calculated by Eqs. (22) and (23).
The computational results compared with the experimental data are shown in Table 2. Experimental conditions for each test run are slso given in this table. The results are also shown grafically from Fig. 5 through Fig. 8.
4) Fig. 9 is the hypothetical drying characteristics of intermittent drying. Figs. 10 and 11 are the computational and experimetal results for intermittent dryings.
The equations in this report better explained the results of intermittent drying and the results of drying using large air volume than the equations in previous report by the same anthers.