EVALUATION OF THIN LAYER DRYING MODELS FOR SIMULATING DRYING KINETICS OF JACKFRUIT SLICES IN A SOLAR GREENHOUSE DRYER

Abstract

Thin layer drying models are important tools in describing drying kinetics and improving the drying process of various agricultural produce. Reliance solely on experimental drying practices without mathematical considerations of the drying kinetics can significantly affect the design of efficient dryers. Simulation of the drying process in dryers by means of mathematical models can help in understanding the drying kinetics as well as in selection of optimal operating conditions of dryers. This study was therefore undertaken to evaluate thin layer drying models for simulating drying kinetics of jackfruit slices in a solar greenhouse dryer. The experimental work involved monitoring air temperature and relative humidity in the dryer, moisture changes of jackfruit slices during drying and eventually mathematical modeling of the drying process. The pulp took 19 hours to reach its equilibrium moisture content of 4.52% dry basis (db) from an initial moisture content of 257.92% (db). In the first four hours, a fast drying rate was observed which thereafter slowed down. Generally, the drying rate increased with increase in temperature and decreased with increase in relative humidity. Four widely used thin layer drying models (Newton, Page, Modified Page, and Henderson and Pabis) were fitted to the experimental data and the best model was selected based on the coefficient of determination (R²), root mean square error (RMSE) and chi-square (c²). The Page model was found to best explain the prediction of thin layer drying of jackfruit slices, based on the highest value of R² and the lowest values of RMSE and c². Overall, the results obtained proved that the Page model is an efficient thin layer model that could be used in enhancing dryer design and processing of jackfruit slices.