Design and Performance Evaluation of a Mixed-Mode Solar Crop Dryer

This study is concerned with development and performance evaluation of a mixed-mode solar  yam dryer. It was done to address the problems of uneven drying of product on different trays coordinate position in a typical indirect multiple trays dryer. Solar energy drying system was designed using the meteorological conditions of Zaria, Nigeria to dry yam slices in the mixed-mode natural convection. The dryer was designed to dry (7 kg) of yam slices. The dimensions of the dryer were: collector length, collector area, height of the drying chamber, chimney height, length of the drying chamber, and Width of the drying chamber were 0.65 m, 0.27 m 2 , 0.9 m, 0.7 m, 0.5 m, and 0.43 m, respectively. The solar yam dryer was exposed to solar radiation from 10:00 am to 06:00 pm and tested without load and with yam chips of 5 mm average thickness. Meteorological conditions were monitored during the dehydration process. The average drying rate, collector efficiency and drying efficiency were 2.55 kg/s, 42.20% and 25.35%, respectively. The results of performance evaluation of the solar dryer showed that the drying rate decreases by 3% and 8% in the second and third trays relative to the first tray. This shows that the drying rates did not vary significantly with the coordinate positions of the trays.