Design and Development of a Mixed-Mode Domestic Solar Dryer

Abstract

This work focuses on the design and development of a mixed-mode domestic solar dryer in which the slices of pepper, okra and yam were dried simultaneously by both direct radiation through the transparent glass roof of the drying chamber and by the heated air from the solar collector. The dryer was made up of the solar collector, the desiccant chamber and the drying chamber which contains a rack of three trays. The air comes in through the air inlet and heated up within the solar collector and then channeled through the drying chamber by natural convection where it is utilized for drying purposes. The development was done using locally sourced and readily available materials such as wood, transparent glass sheet, mild steel metal sheet, mosquito galvanized wire mesh and chicken galvanized wire mesh. The maximum temperature attained by the solar collector, drying chamber during test were 69oC and 55oC respectively, with a corresponding ambient temperature of 39oC. The mass of water removal of 43g, 136g and 255g from pepper, okra and yam slices respectively was achieved making use of the passive solar food dryer as against the water removal of 39g, 126g and 218g from pepper, okra and yam slices respectively achieved using the sun drying method which indicates a difference of 4g, 10g and 37g for pepper, okra and yam slices respectively. The rapid rate of drying achieved with the use of this dryer shows that it has the ability to dry food items rapidly to an acceptable moisture content level.