Dehydration Characteristics of Whole Lemons in a Convective Hot Air Dryer

In this study, whole lemons were dried using a laboratory convective hot air dryer and the effects of drying temperature on dehydration behaviour and mass transfer characteristics of the lemons were investigated. The drying experiments were conducted using air temperatures of 50, 60 and 75 °C and air velocity of 1 m/s. It was observed that the drying temperature affected the drying time and the drying rate significantly. Drying rate represented no constant period and the entire dehydration process took place in the falling rate period. The usefulness of five mathematical models to simulate the drying kinetics was evaluated and Midilli and logarithmic models were found as the best models describing the drying curves. The effective moisture diffusivity values were obtained to be 1.15×10^-10, 2.29×10^-10, and 7.63×10^-10 m^2/s for the applied temperatures, respectively. The activation energy was also determined to be 71.32 kJ/mol. The convective mass transfer coefficient values were calculated by the analytical model and obtained to be 4.078×10^-7, 1.023×10^-7 and 4.346×10^-8 m/s for drying temperatures of 75, 60 and 50 °C, respectively.