Experimental Study of a Mixed Solar Dryer: Application to Drying Okra

Large-scale agricultural production generally occurs during specific periods of the year. This results in the unavailability of products outside of their production periods. Due to their high water content, most agri-food products deteriorate very quickly under the effect of heat, hence the need to develop preservation techniques. Preservation techniques for fresh produce require energy. Burkina Faso is a country with strong solar potential, which is why solar dryers are the most developed technologies for preserving agri-food products. However, the quality of the dried product depends on the quality of the dryer. Our work focuses on the construction of a mixed solar dryer for drying agricultural products. The flat-plate collector is equipped with baffles that allow for greater heat exchange between the air and the hot parts (absorber and baffles) of the collector. The drying chamber is fitted with double-sloped glazing on the roof. An experimental study of hygrothermal parameters, such as air temperature at the racks, product temperature, product water content, and relative humidity inside the drying chamber, was conducted to determine the dryer's performance. We also determined the effective diffusion coefficient and efficiency. The evolution of solar irradiation was monitored during drying operations. Experiments show that the temperature inside the dryer can reach 80°C to 100°C. The effective diffusion coefficient is approximately 1.89.10<sup>-7</sup> m<sup>2</sup>/s, and the dryer's efficiency is 28.56%.