Convective Drying and Mathematical Modeling of Onions Dried Using a Flat Plate Solar Air Heater
Abstract:
Solar drying of fruits, vegetables and grains is the oldest processing
technique used for food preservation. In this research a flat plate solar air
heater having an efficiency of 20% was used for drying onion flakes. The solar
air heater assembly provides a temperature in the range of 40-50°C and humidity
10-30% in each day of drying period to the drying section. The drying section
provides a total of 6 hours period per day as a suitable range for onions drying.
Onions were dried and drying curves were developed for the drying kinetics of
onions. The initial moisture in onions was 93% which was reduced to 5%. The
moisture loss curve shows that onions lost 11% in each hour at an average. The
drying curves of drying rate shows that the average drying rate of onions was
0.30 gH2O. gDM/h. Five published models (Newton, Page, Modified Page, Two-term
expo and Wang) were tested to find relationship of drying curves with drying
time. Among the five models Two-term expo model was the best describing drying
kinetics on onions with R2 value 0.974 and Root Mean Square Error
0.447 for moisture lost and 0.953 and 0.451 for drying rate. It was concluded
that flat plate solar air heater dries onions in short period of time. The quality
of onions dried by a flat plate solar air heater may be better than open sun
drying system. Among the five models Two-term expo model was the best describing
drying kinetics on onions.
How to cite this article
Muhammad Hanif, Masood Ur Rahman, Muhammad Amin, Mansoor Khan Khattak, Muhammad Ramzan, Subhan Ud Din and Khanzeb Khan, 2013. Convective Drying and Mathematical Modeling of Onions Dried Using a Flat Plate Solar Air Heater. Pakistan Journal of Nutrition, 12: 1003-1007.
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