Heat and Mass Transfer, Quality, Performance Analysis, and Modeling of Thin Layer Drying Kinetics of Banana Slices

In this study, experimental works were carried out in three different drying methods named heat exchanger-evacuated tube-assisted drying system (HE-ETADS), greenhouse solar dryer (GHSD), and open sun drying (OSD) to compare thin-layer drying kinetics, concept of mass transfer, and quality assessment of banana slices. Initial moisture content (MC) of banana slices was obtained as 78 +/- 2.0% (wb), which decreased to 23.2 +/- 2.0% (wb), 25.6 +/- 2.0% (wb), and 28.8 +/- 2.0% (wb) in all three drying systems, respectively, in 9 h of drying time. Average drying rate was evaluated as 7.89, 7.65, and 7.25 g water/g solid h in HE-ETADS, GHSD, and OSD, respectively. Weibull model (WM) defines thin-layer drying kinetics of banana slices in all three drying processes. Maximum hardness and shrinkage factor of dried banana slices were obtained as 373.6 g and 75%, respectively, in HE-ETADS. Effective moisture diffusivity, activation energy, and mass transfer coefficient were computed as 1.11-2.48x10(-07) m(2) s(-1), 30.25 kJ/mole, and 3.21-1.0 x10(-04) m/s, in HE-ETADS. Similarly, in GHSD and OSD, these factors were observed as 1.21-2.34 x10(-07) m(2) s(-1), 41.25 kJ/mole, 3.15-1.0 x 10(-04) m/s and 1.3-2.21x 10(-07) m(2) s(-1), 56.89 kJ/mole, 3.01-1.0 x10(-04) m/s. Maximum total color changes were noted in OSD. Hence, HE-ETADS can potentially dry high moisture content crops effectively within a minimum drying period.