Determination of drying constants and their dependence on drying air parameters for thin layer onion drying

An experimental through dryer with continuous weighing system was developed for determining the drying late constants for thin layer drying of onion (Allium cepa L, variety: Agrifound White- I). Drying characteristics of onion were examined using ambient heated air for a temperature range of 50-80 degrees C and air now velocity range of 0.25-1.00 m/s. The influence of drying variables on drying rate constant was explained suitably by Arrhenius type equation. This was also compared with Power model. The models were tested with data produced in an experimental through dryer, using nonlinear regression analysis. The Arrhenius type model predicted the moisture ratios well at the experimental drying conditions.