RESULTS AND DISCUSSION
Establishment of Thin-layer Drying Equations
and Effective Diffusion Coefficient
The empirical models developed from experimental data
at different drying temperatures and initial moisture contents
are shown in Table 1. The best empirical model
describing the thin-layer drying characteristics was chosen
as the one with the highest correlation coefficient (r2) value
and the lowest MRS value. Table 1 shows that the r2 value
varied between 0.926 and 0.999 while the MRS value varied
between 0.002 and 0.005. The logarithmic function was in
good agreement with experimental results as compared to
the other empirical models. To validate the logarithmic
model, the predicted and observed data under the condition
of one-direction air flow and constant drying temperature
of 100C for crumb rubber at an initial moisture
content of 45.0% dry basis is presented in Fig. 5. This
shows that the simulated results were in good agreement
to the experimental results.
Such substituting of diffusion models into the analytical
solution of thin-layer drying equations of Eq. (2) and the
effective moisture diffusion coefficient (D) was calculated
using nonlinear regression analysis. The following effective
diffusion coefficients equation can be written as:
For infinite slab: