Thin layer of apple chips (‘Golab’) with 73.4% (wet basis) moisture content were dried in a hybrid solar dryer. A new mechanism was designed to change inclination of the collector. Drying experiments were run in three levels of airflow rates and two levels of collector tilted angle. In order to describe the thin layer drying, ten different models were selected. The goodness of fitting was evaluated by calculating and comparing the statistical values for each model. The approximation of diffusion and the Midilli model were chosen for 30, and 45 degrees of tilted angle, respectively. Besides, five linear and nonlinear equations were derived in order to establish the best relationship for every empirical coefficient with temperature and airflow rate. Results revealed that the 2nd polynomial equations were suitable to predict these coefficients. Comparison between moisture ratio data in different inclination evidenced that more drying intensity occurred with 30 degrees of slope angle and airflow 0.018 m3・s-1.

solar dryer, variable collector, drying model, apple

Published by University of Zagreb, Faculty of Agriculture, Zagreb, CROATIA
Sponsored by Ministry Science and Education of the Republic of Croatia