Experimental and Theoretical Investigation of Pumpkin Drying in Fluidized Bed Dryer

Abstract

Thin layer drying characteristics of pumpkin cube were experimentally investigated in a fluidized bed dryer. Experiments were performed at three different drying temperatures: 50, 60 and 70 °C. Pumpkin used in the experiments had an initial moisture content of 95% wet basis (1930 % dry basis). The drying air velocities were set to 3.5 m/s to achieve fluidization. Experimental results show that large drying rates are obtained in the fluidized bed dryer, which are much higher than those obtained with conventional methods and convective tray dryer. In just 120 minutes moisture contents lower than 6% wet basis were achieved. Pumkin drying was mathematically modeled using the Lewis, Henderson ve Pabis, Page, and logaritmic models, all of which are semi-emperical models widely applied in the literature. Using Fick’s first law effective diffusivities were calculated and compared with those in the literature. Effective diffusion coefficients obtained in the fluidized bed dryer were up to 70% higher than the diffusion coefficients obtained in convective tray dryers. Temperature dependence of effective diffusion coefficients was described by an Arrhenius-type relationship.