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Solid desiccant regeneration by direct solar energy for fresh fruit drying

Conference · · ASAE Publ.; (United States)
OSTI ID:6486156
Direct solar drying was investigated to regenerate activated alumina and silica gel for their subsequent use as an energy store. The contemplated application is for dehumidification to condition air to a low absolute humidity. The air would then be used to dry surface moisture from whole fruit in packinghouse applications. Both desiccants were regenerated to less than 66 percent of their initial moisture content. Variables studied were: air flow rate, desiccant loading and type of desiccant. Solar efficiency was calculated based on total insolation, moisture loss and the heat of adsorption. Both total moisture loss and solar energy utilization were positively correlated with total moisture available for vaporization. Overall utilization levels ranged from 18.4 to 27.3 percent for silica gel over 12-h (2 days at 6 h) test period. An energy balance of the solar drying process indicated substantial losses in the exhaust air stream, through thermal losses and by transmittance-absorptance reductions. With the partial regeneration accomplished in flat-plate tests, volumetric energy capacity for silica gel is significantly greater than rock bed or water systems. A moisture content spread of 17.5 percentage points is equivalent to a water temperature rise of 112/sup 0/C for equal storage volumes. Research is continuing with an integrated fruit drying unit and a continuous belt regenerator.
OSTI ID:
6486156
Report Number(s):
CONF-8009144-(Vol.3)
Conference Information:
Journal Name: ASAE Publ.; (United States) Journal Volume: 5-81
Country of Publication:
United States
Language:
English