FIELD EVALUATION OF SOLAR TUNNEL DRYER FOR GRAPES DRYINGVijayakumar Palled, S.R. Desai and M. Anantachar
A study was conducted to evaluate the performance of solar tunnel dryer of 18 m X 3.75 m size with shade net for grapes drying at farmers field. The results indicated that a maximum temperature of 62 °C was recorded at 14:00 hours inside the solar tunnel dryer during drying process which was 42.74 % higher than the maximum ambient temperature (35.5 °C) at the same time. On an average, a total drying time of 60 drying hours (8 9 sunny days) were required for solar tunnel dryer to reduce the moisture content of grapes from 82 % (w.b.) to a final moisture content of 14 % (w.b.) while the traditional method of shade drying required on an average 140 drying hours (20 21 sunny days) to obtain same level of moisture content. This resulted in a net saving of 57.14 % in drying time for solar tunnel dryer over open shade drying. The dehydration ratio of the product was worked out to be 4:1. It was observed that the net returns obtained for the solar tunnel dryer was found to be Rs. 7790 per tonne of grapes dried with a benefit to cost ratio of 1.26, while for traditional method of drying it was Rs. 1570 per tonne with a benefit to cost ratio of 1.05. The payback period for the solar tunnel dryer worked out to be 1 year.
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