A natural convection solar tunnel dryer comprising three major units, a solar collector unit, a drying unit, and a vertical bare\nflat-plate chimney, was constructed. No-load tests with a horizontal configuration of air entry into the collector resulted in a\nbidirectional air flow in the dryer. To correct this undesirable situation, an air guide at the collector was incorporated to ensure\nthat air entered in a vertical direction. To investigate its performance, drying experiments with mango were carried out at the\nUniversity of Zambia, Department of Agricultural Engineering. Uncertainties in the parameters measured in the experiment were\nanalysed and quantified. The results showed that, under solar radiation between 568.4 and 999.5W/m2, air temperature of up to\n65.8âË?Ë?C was attained at the collector unit.Theaverage relative humidity values were 30.8%, 6.4%, and 8.4% for the ambient, collector,\nand drying unit, respectively.Under these conditions,mango with an initialmoisture content of 85.5% (wet basis) was dried to 13.0%\n(wet basis) in 9.5 hours. The collector, drying, and pick-up efficiencies were found to be 24.7%, 12.8%, and 35.0%, respectively.The\naverage temperature difference between the chimney air and ambient air was 12.1âË?Ë?C, and this was sufficient in driving the flow of\nair through the dryer.
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