Performance evaluation of a rotary dryer for onion bulb drying

Drying is conducive in extending the storage life of fresh harvested onion. Currently, direct sun drying is not suitable in terms of fluctuating weather conditions. Rotary dryer assisted by combustion heating is a viable option to speed up onion drying process. In this case, 10 kg of fresh onion was placed in a rotary dryer operating for 2 hrs at 40°C and 14.6 m/s of air velocity. Moisture content was observed at every 30 mins and drying rate was predicted using several mathematical models. The drying temperatures were 50, 60, 70°C and the drying procedures were repeated. Results showed that the rotary dryer method can improve drying performance compared to the chamber and tray dryer methods and the drying rate of onion bulb drying can be well represented by the Page’s model with R 2 value near to 1, and the lowest average chi-square (X2 ) of 0.00027.