Design, realization and comparison of three passive solar dryers. Orange drying application for the Rabat site (Morocco)

Abstract

This research carried out on drying kinetics and quality of dried orange slices in three indirect solar dryers with natural convection, to compare the thermal performance of solar dryers, a data acquisition system is used to follow the evolution of climatic variables (temperature, relative humidity, solar radiation).The experimental measurements for several days in April and May show the average temperature does not exceed 19.5 °C, while the average internal temperatures are 40 °C for Dry3 (the third solar dryer), 34 °C for Dry1 (the first solar dryer) and 28 °C for Dry2 (the second solar dryer). While the relative humidity of the outdoor environment varies in the interval [60%, 85%]. For the relative humidity into dryers, it is observed that the values are ranging in the intervals [5%, 35%] for Dry3, [5%, 70%] for Dry1, and [32%, 75%] for Dry2. Based on these obtained climatic conditions, drying the orange slices is carried out. It was found that the orange slices lost 72% of their initial mass after 6 days in the Dry3, after 15 days for Dry1 and after 18 days for Dry2.The study'’s main experiments have shown that a special formulated the third solar dryer is most effective through thermal performance and drying duration, in terms of economic costs, the design of the Dry3 with a single compartment is less expensive than conventional two-compartment solar dryers. So, Dry3 is beneficial and encourages its use by the local producer.