Development of Small Scale Direct Mode Natural Convection Solar Dryer for Tomato, Okra and Carrot

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Author(s) Eke, Ben Akachukwu
Pages 199-204
Volume 3
Issue 2
Date February, 2013
Keywords Vegetables, Moisture, Solar, Dryer, System drying efficiencies.


Three small scale direct mode natural convection solar dryers were developed with locally affordable and available materials, to solve the problems local farmers encounter in handling vegetables such as, tomato, okra and carrot. Each of these crops was sliced at the thickness of 15mm and each sample loaded in single layer in a particular dryer and dried at the same time. The samples were also dried in open sun as control. Weather factors that affect crop drying, heat energy generated by the dryers and the rate of crop drying were monitored at the intervals of two hours in the day time. Results showed that sliced samples of tomato, carrot and okra dried with solar dryers, achieved 54.55, 52.88 and 50.98 percent gain in drying time respectively, when compared with open sun drying. Results equally indicated that tomato, carrot and okra, were dried at average daily solar dryer temperature of 49.9oC, 51.17oC and 52.29oC respectively. The analysis revealed that tomato, carrot and okra dried in solar dryers attained 21.80, 21.18 and 24.95 percent system drying efficiencies for tomato, carrot and okra respectively. While the open sun achieved 10.59, 12.71 and 15.19 percent system drying efficiencies for tomato, carrot and okra respectively. These results showed that drying of vegetables can best be achieved by solar dryers than open sun drying. This work indicated that onion cannot be dried in open sun because the pungent aroma is usually lost when exposed to unconfined space.

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