Abstract:
The indirect forced convection solar drying has an advantage in preserving perishable food items with unlimited solar accessibility, purely renewable energy forms and fast drying time. It has sound benefits compared to other forms of solar drying techniques by controlling internal and external factors that alter the drying quality and system efficiency.
Ethiopia one of the Sub-Saharan countries found under the tropical solar belt having Twelve months of sunshine has an advantage of using solar energy at natural reliability. The country with large population and rapid economic growth has low food security. The indirect forced convection solar dryer can be a means to avoid agricultural product losses especially during the time of peak harvest.Ginger, an excellent spice found in every kitchen has been dried using the indirect forced convection solar dryer. Ginger has been chosen because, it contains 89% moisture on weight basis having wild spoilage rate. The dryer has an advantage over other forms of drying by short drying time, normal food properties. To design the dryer, thorough heat and mass transfer analysis, energy balance and material selection have been performed. As per the design, the dryer structure has been entirely made of wood, aluminium-absorber, glazing and DC-fan. It has three trays with loading and unloading table. Useful measuring devices were used to record the data appropriately for three samples each having three runs with a total of nine experiments. The experiment has been carried out at Bahir Dar town on the month of March from 06-2018 to 28-2018. From observed data analysis, the temperature value at chamber outlet and trays show low values as more moisture is released and increases as moisture removed from ginger decreases. Contrary to temperature, efficiency of the dryer increases when moisture removed from ginger increases. Thermal efficiency rises as air mass flow rate increases. The final moisture content were found to be 6% on wet basis and 0.54 on dry basis. Thin layer mathematical modelling was done to determine the moisture ratio at any drying time and Newton modelling has got favour than Lewis and Pabis model.