| Resumo: |
The drying process of turnip and drying rate curves were investigated at different temperatures (55, 70 and 85°C) with air flow rate of 1.5 m/s. Also effective diffusion coefficient and activation energy were calculated by using Arrhenius equation and Fick’s second law for infinite slab. The effective diffusivity varied between 5.471×10-10 and 8.966×10-10 in the range of (55°C to 85°C). The value of activation energy was found to be 16.013 kJ/mol. The mathematical models (Newton, Page, Modified Page, Henderson and Pabis, Logarithmic, Two term, Two term exponential, Wang and Singh, Simplified Fick’s diffusion, Modified Page –II, Verma, Midilli–Kucuk, Hii, Law and Cloke, Approximation of diffusion, Modified Henderson and Pabis) were fitted to the experimental data. Sigmaplot v10.0 software was used to find the best model for evaluating the rate of moisture change. Decency of fit by these models was based on comparing the coefficient of determination (R2), reduced chi-square (χ2), mean bias error (MBE) and root mean square error (RMSE) between the observed and predicted variables. Among 15 evaluated models, Modified Henderson and Pabis in 85°C and Hii, Law and Cloke in 55°C and 70°C with highest R2 and lowest MBE, χ2 and RMSE were selected to better estimate the drying curves.Keywords: Turnip, hot air convective drying, modeling, drying rate, effective diffusivity, activation energy
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