Experimental Study of a Direct Solar Dryer with an Automatic Temperature Control System

Preventing post- harvest losses is an imperative for human populations. Drying is one of the various conservation techniques. This is an operation that requires a fair amount of energy, hence the need to use available renewable energies such as the sun. For countries with a lot of sunshine, solar dryers are an asset for preserving agriculture products. However, the dryers traditionally used do not perform satisfactorily, hence the need to develop 'modern' dryers. The present work concerns the design and study of a direct solar dryer whose internal temperature can be regulated. The experimental study consisted of monitoring the temperature of the drying air in the dryer at no load and under load, monitoring the moisture content of the products being dried and determining the dryer's output. The products to be dried were okra and tomatoes. The results of the no- load test showed that the air can reach a temperature of 84°C in the dryer. During drying, the average temperatures recorded in the dryer were around 58°C and 56°C for okra and tomatoes respectively. The drying kinetics showed only one phase, the decreasing phase. The average thermal efficiency of the dryer is 22%. The results obtained are appreciable. Keywords: direct solar dryer, temperature, regulation, drying kinetics, efficiency