Study on Hybrid Drying with Infrared Radiation of Watermelon Seeds (Citrullus Lanatus)

Abstract

Drying characteristics of watermelon seeds using infrared (IR) heating combined to non-heated air flow were determined varying the IR source temperature and air velocity. The effects of the process variables on the effective moisture diffusivity (Deff) and specific energy consumption (SEC) were also evaluated. Experiments in the hybrid dryer were conducted with seeds arranged in a single layer and exposed to three IR temperatures levels (45, 65 and 85 W/m2) and three air velocities levels (0.4, 0.8 and 1.2 m/s) at 25°C. The effective moisture diffusivity was estimated using Fick’s diffusion model assuming negligible shrinkage and surface moisture in equilibrium with the surrounding air. Deff-values ranged from 0.62 x 10-10 to 1.83 x 10-10 m2/s, while SEC-valued varied from 29.91 to 73.16 kWh/g. Statistical analysis carried out on the experimental data indicated that the effective moisture diffusivity and specific energy consumption were significantly influenced only by the IR source temperature, which had a positive linear effect on Deff and a negative linear effect on SEC. Maximum effective diffusivity and minimum energy consumption values in hybrid drying of watermelon seeds were obtained with the use of the highest IR temperature and lowest air velocity.