Abstract
The main aim of this study was to develop an integrated solar-tracking system to maximize the efficiency of solar heaters manufactured from recyclable aluminum cans (RAC) for optimum drying of apple slices. The results revealed that the thermal efficiency of the solar air heater incorporated with a tracking unit was significantly improved by about 45% compared with the conventional fixed heaters at all tested air flow rates. The highest thermal efficiency of 87.1% of the solar air heater equipped with a tracking unit was achieved at the highest air flow rate of 44 m(3)h(-1). The effective moisture diffusivity (D-eff) increased at the high levels of drying air temperature and flow rate and the highest value of D-eff (5.43 x 10(-10) m(2)s(-1)) was obtained in the dryer with a tracking system at the highest air flow rate of 44 m(3) h(-1). The drying rate of apple slices under such a tracking module was considerably higher than that of either the traditional fixed system or the ambient sun drying. (c) 2020 Elsevier Ltd. All rights reserved.