Crop drying by indirect active hybrid solar – Electrical dryer in the eastern Algerian Septentrional Sahara

In the present work, a new specific prototype of an indirect active hybrid solar–electrical dryer for agricultural products was constructed and investigated at LENREZA Laboratory, University of Ouargla (Algerian Sahara). In the new configuration of air drying passage; the study was done in a somewhat high range of mass flow rate between 0.04 and 0.08 kg/m2 s a range not properly investigated by most researchers. Experimental tests with and without load were performed in winter season in order to study the thermal behavior of the dryer and the effect of high air masse flow on the collector and system drying efficiency. The fraction of electrical and solar energy contribution versus air mass flow rate was investigated. Slice tomato was studied with different temperatures and velocities of drying air in order to study the influence of these parameters on the removal moisture content from the product and on the kinetics drying and also to determine their suitable values. Many different thin layer mathematical drying models were compared according to their coefficient of determination (R2) and reduced chi square (χ2) to estimate experimental drying curves. The Middli model in this condition proved to be the best for predicting drying behavior of tomato slice with (R2 = 0.9995, χ2 = 0.0001). Finally an economic evaluation was calculated using the criterion of payback period which is found very small 1.27 years compared to the life of the dryer 15 years.