Mathematical modeling and drying characteristics of thin layer drying of bitter gourd in evacuated tube solar dryer-without heat pipe

Abstract

Evacuated tube solar dryer-without heat pipe (ETSD-WHP), also called direct flow evacuated tube solar dryer was used for preservation and quality analysis of bitter gourd (Momordica charantia). Mathematical modeling with eight semi-empirical models and drying characteristics of bitter gourd were carried out in the current study. Bitter gourd was dried in 12 hours from an initial moisture level of 91.85 % to a final moisture level of 6.77 %. The maximum rate of mass removal (drying rate), was found to be 15.15 g moisture/g dry matter/hr at 1 PM when solar radiation was high i.e 735 W/m2. Among all models, the Midilli and Kucuk model was found best fitted for bitter gourd with R2, χ2, and RSME values of 0.9982, 2.43×10-4 and 0.0129, respectively. From the quality analysis, it was observed that the color and water activity of bitter gourd decreased after drying significantly.