Abstract:
Paddy, the major staple food source used in Sri
Lanka is subjected to many thermal treatments before
consuming since the moisture content of the paddy must be in a
desirable level for milling and storage purposes. Drying
characteristics of two types of parboiled paddy (“Nadu” &
“Samba”) were investigated in a packed bed dryer. Drying
experiments for both paddy types were carried out at three
different hot air temperatures 35oC, 45oC and 55oC by keeping
hot air flow velocity and bed height constant as 0.98 m/s and 0.15
m respectively. Experimental results were fitted to three thin
layer drying models; Midilli et. al., Weibull et. al. and Page.
Statistical indicator; Root mean square error (RMSE) showed
Midilli et. al., Weibull et. al. models give better fit to the
experimental values. The drying curves lie totally in the falling
rate period since the drying rate is controlled by the moisture
diffusion of bound water. Maximum drying rates and Effective
moisture diffusivity values were determined for different
temperatures. The Activation energies of “Nadu” and “Samba”
calculated based on the Arrhenius equation are 16774 J/mol and
19611 J/mol respectively.
