Design and construction of a maize on cob solar drier

Abstract

Drying is one of the traditional methods of maize preservation. Drying as a process has been practiced over years. It is performed in various ways which include sun drying or forced convection. Sun drying technique such as natural sun and forced convectional technique, which solemnly vary due to the source of heat supply. The sources can be diesel heaters or solar evacuated tubes. In Africa most of the farmers harvest maize while on cobs and move it into granaries. During rainy season, the harvest is delayed and the maize absorbs more water, increasing the risk of spoilage when piled. Storing wet grains for weeks in granaries predisposes the crop to fungal contaminants such as mycotoxins. This may be avoided by artificially drying the maize after harvest. This research work proposes a more efficient and optimal design to dry grains on the cob using solar energy. A dryer was designed, fabricated and then tested. The design involved simulation of the shape and size of the drying chamber, along with its airflow distribution using SolidWorksTM. The amount of heat required, the arrangement of the solar evacuated tubes housing and the quantity of air to dry were determined. The dryer was fabricated to handle approximately one bag of maize on cob and consisted of a drying chamber, a solar heat collector comprising solar evacuated tubes and a blower. The solar heat collector was able to heat the air from a temperature of 27.1 0C to 56.7 0C and 7 kg of maize on cob was dried from an initial moisture content of 25.7%wb to 13.4%wb in two days, with six hours of operation per day. A moisture content of 13.5%wb and below is recommended for safe storage. The fabricated dryer reduced time of drying, producing clean dried maize and could therefore be used to enable farmers to have a good investment return during post-harvest handling of maize on cob in rainy seasons. It could also be used in empirical research to determine the air velocity and temperature for optimal drying of maize on the cob.