Mathematical modelling of mixed mode natural convection solar drying of tomato slices

Abstract

The objective of the present investigation was to study the drying kinetics of tomato (Lycopersicon Esculentum) slices at different drying loads in a fabricated mixed mode natural convection solar dryer. Tomato slices were dried to the safe level moisture content in a period of 20 h, 23 h and 30 h with the drying loads of 2 kg/m2, 4 kg/m2 and 6 kg/m2, respectively. The solar dryer was constructed at a low cost with locally obtainable materials. Nine different thin layer mathematical models were chosen to fit to the experimental data. The models were compared using the correlation coefficient (R2), root mean square error (RSME) and the reduced chi-square (χ2). Among all these models, the approximation of Two-term was shown a better fit to the experimental drying data compared to other model for 2 kg/m2 and 4 kg/m2 whereas the Logarithmic model was shown a better fit for a 6 kg/m2 of drying load. The dryer efficiency increased from 17.33% to 35% with increased in drying loads from 2 kg/m2 to 6 kg/m2.