Experimental investigation of a direct solar dryer equipped with parabolic-trough solar concentrator for drying Moringa leaves in the region of Algerian sahara, Ouargla city

The thermal performance of a direct solar dryer (DSD) is experimentally scrutinized in the present study under the prevailing conditions in Ouargla city (31°57′N 5°19′E), Algeria. For this purpose, two DSDs were designed and constructed: first, a conventional dryer and second is a modified dryer where a parabolic trough solar concentrator (PTSC) is connected to a heat exchanger fixed at the bottom of the drying chamber. First, the effect of mass flow rate ($\dot{m}$) of the heat transfer fluid (HTF) (water) on the performance of modified DSD was studied. Then, the modified dryer was used for drying Moringa leaves. The experimental results reveal that the lowest value of the $\dot{m}$ (0.007 kg/s) achieves highest drying performance. It is also found that the drying air temperature of the modified DSD is 6–11.3 °C above ambient, compared to 4–10.0 °C for the conventional DSD. This high improvement, which reaches 37.6 %, proves the effectiveness of integrating the PTSC with DSD. A high drying rate, of 0.732 kg water/h. kg (dry matter), was achieved when Moringa leaves were dried in the modified DSD as it loses 76.7°%wb of their moisture content after only 4.5 h. New empirical equation was used in this study for fitting the thin layer drying characteristics of Moringa leaves in the modified DSD under climatic conditions of Ouargla, Algeria.