Design and Construction of a Mixed-Mode Natural Convection Solar Dryer for Mango Slices

Abstract

Fruits like mangoes are produced in large quantities during the peak season, and high postharvest losses occur due to lack of appropriate storage and handling structures. The main goal of this study was to design and construct a mixed-mode natural convection (MMNC) solar dryer for drying of mango slices. The dryer was designed using AutoCAD and constructed with wood and glass using basic woodworking tools and processes. The developed dryer has a direct collector, a vertical collector, and an indirect collector. The drying chamber has two removable frames with 5 shelves each, a total drying area of 2.54 m2 and a capacity of 10 kg of mango slices per batch. The dryer is fitted with caster wheels for easy turning and positioning. Test conducted with 940 g of fresh mango slices resulted in effective drying after 17 hours, from a moisture content of approximately 90% (wb) reduced to 17% (wb). The drying rate was found to be 4.3%/hr. The maximum temperature obtained in the drying chamber was 54.3 ℃ at a maximum ambient temperature of 37.6 ℃. The average temperature-rise in the drying chamber compared to the ambient temperature was 11.5 ℃. The dryer is therefore recommended for use both domestically and by small-scale food processors since it is more hygienic and has proven to be more efficient than open-air sun drying.