Sour lemon drying by hot air drying under ultrasonic pre-treatment

The purpose of this research is to obtain the thermodynamic properties of lemon drying under the influence of ultrasonic pre-treatment in a hot air dryer. Experiments were performed using a convection dryer with ultrasound pretreatment in 40, 55 and 70 °C air temperature, 1 m/s air velocity and duration of ultrasonic pre-treatment of 0 min (for control sample), 10, 20 and 40 min. The drying kinetic of the lemon was estimated by 14 mathematical models. The results showed that the drying time decreased with increasing the air temperature and the time of applying ultrasound. The best model to predict the drying of lemons was selected by Midilli et al. The use of ultrasonic pre-treatment at different temperatures resulted in a significant increase in the effective moisture diffusivity ( ) from 5.04×10-11 to 2.00×10-10 m2/s. Activation energy ( ) of the lemon was obtained between 34.93 and 42.97 kJ/mol. The values of specific energy consumption ( ) were 47.39 to 240.46 kWh/kg.