Experimental computational study on drying of Black Cumin (Nigella sativa) in a fixed bed dryer and in a Thermo-gravimetric analysis system

Abstract

In this study, drying of black cumin seeds (BCs) (Nigella sativa) with initial moisture content (MC) of %56.74 (dry basis (d.b)) was investigated in a novel designed fixed bed drying system (isothermal condition) and in a thermo gravimetric analysis system (non-isothermal condition). In isothermal conditions, the drying experiments were carried out at different temperatures (40, 60, and 80 °C) and air velocities (0.25, 0.5 and 1 m/s) and bed heights (14 mm and 28 mm). Several models in literature were selected to fit the experimental data. The fit quality of models was evaluated using the coefficient of determination (R2), sum square error (SSE) and root mean square error (RMSE). Two term model has a good agreement with the experimental data and gave the best results for BCs. The activation energy was calculated to be as 19.92 kJ/mol and effective diffusivity values were calculated to be between 2.85×10-10 and 6.77×10-10 m2/s depending on air temperatures. Furthermore, drying and decomposition behaviours of BCs in thermo gravimetric analysis system were studied in nitrogen flow of 0.850 ml/s and of constant heating rate of 5 °C/min towards 250 °C by means of non-isothermal methods.