Evaluation of thin-layer drying models
Figure 3 shows the decreasing trend of moisture ratio with drying time. The three equations mentioned in Table 1 were fitted to the experimental data for Pandanus leaves. The higher the value of coefficient of determination (R2) and lower the value of RMSE and chi-square (χ2), the better the criteria for goodness of fit. The main parameters, R2, chi-square and RMSE of the three model equations for Pandanus leaves dried under different conditions are shown in Table 2. It can be observed that mean values of R2 was highest and the corresponding values of chi-square and RMSE values were lowest for the Page’s thin-layer drying model for both the conditions. Hence, Page’s model was considered as the best model to describe the thin-layer drying of Pandanus leaves. In both the cases the values of R2 for Page model were greater than an acceptable threshold of 0.90, indicating better goodness of fit. It was concluded that Page model can be used to estimate the moisture content of Pandanus leaves at any time during the drying processes at different conditions with acceptable accuracy. The coefficients of the different models fitted at the different temperatures are reported in Table 2. The accuracy of the established model for the low temperature drying process was evaluated by comparing the predicted moisture ratio with observed moisture ratio. The performance of the model for both the drying temperatures has been illustrated in Fig. 4. The predicted data generally banded around the straight line which showed the suitability of the Page model in describing the drying behaviour of Pandanus leaves in the low temperature drying. The rate constant, K, which is a measure of the drying rate is not significantly different at two different temperatures (p