Design and Development of a Forced-Convection Solar Dryer: Application to Beetroot Cultivated in Béchar, Algeria

The aim of this study is to design, build, and evaluate an indirect forced convection solar dryer adapted to semi-arid climate, such as that of Béchar situated in the west south region of Algeria. The tested drying system consists of a flat-plate solar collector, an insulated two-chamber drying unit, and an Arduino-controlled device that ensures uniform temperature distribution and real-time monitoring using DHT22 sensors. Drying tests were conducted on locally grown beet slices at air temperatures of 45°C, 60°C, and 80°C, with a constant air velocity of 1.2 m/s and a mass flow rate of 0.0027 kg/s. The collector reached a maximum temperature of 65°C, with thermal efficiencies ranging from 20% to 35%. In these conditions, the drying times were cut down to 200–300 min, and the beet’s moisture content dropped to 0.47, 0.27, and 0.24 g/g dry matter, respectively. The experimental data were fitted to several empirical models, including the logarithmic model. The modelled results showed strong agreement with the experimental ones (correlation coefficients r = 0.9919–0.9989; standard errors SE = 0.017–0.043; root-mean-square errors RMSE = 0.016–0.027). The results demonstrate that the system operates efficiently and consistently, making it suitable for the sustainable drying of agricultural and medicinal products in arid climates.