Assessment of constant and time-varying temperature schemes on the convective drying characteristics of hemp leaves

In the present study, selected mathematical drying models are evaluated for describing the convective drying of hemp (Cannabis sativa L.) leaves. Drying kinetics have been experimentally investigated in a laboratory scale convective dryer for a constant airflow velocity of 1 m s-1 and air-drying temperatures of 40, 50 and 60 °C. Non-stationary temperature conditions were also investigated for the same temperature range, under different advancing time-varying temperature profiles. Weibull formula was the most suitable mathematical expression for describing the drying kinetics for both stationary and non-stationary drying conditions. Drying at increased heating rates led to a lower final moisture content compared with the constant drying temperature levels, exposing the raw material for a shorter duration to the higher air-drying temperature.