Drying kinetics, mass transfer parameters, and specific energy consumption analysis of watermelon seeds dried using the convective dryer

Abstract

Convective tray drying of watermelon seeds was conducted to investigate the drying kinetics, mass transfer parameters, and specific energy consumption at different temperatures of 40, 50, and 60 °C and a fixed air velocity of 1.5 ms−1. The drying characteristics were determined by moisture ratio, moisture content, drying rate, and drying time by the drying curves. It was observed that the drying characteristics of watermelon seeds were significantly affected by drying temperature. Eight semi-empirical models were utilized to predict the best model for thin-layer drying kinetics of watermelon seeds. Midilli-kucuk (χ2 = 7.70 × 10−6, RMSE = 0.0109, R2 = 0.9995) model was found to be the best fit for experimental drying curves. Effective moisture diffusivity was found to be in the range from 1.79 × 10−10 to 3.39 × 10−10m2/s with a moderate activation energy of 27.66 kJ/mol. From the investigation of mass transfer parameters, it was observed that the diffusion of moisture was controlled by internal and external resistance of the drying phenomenon. The low specific energy consumption i.e. 524.09 kWh/kg, high diffusion, and the convective mass transfer coefficient was obtained at a higher temperature, hence recommended to dry watermelon seeds at 60 °C temperature.