Numerical and experimental evaluation of the thermal and dynamic performance of a phase change material in an indirect solar dryer

Abstract

The use of solar dryers can be limited due to inherent challenges such as the non-uniform final moisture content of the dried product and the non-continuity of the drying process. These drawbacks are mainly due to the uneven distribution of air between the trays and the intermittent availability of solar energy. Consequently, a storage unit is needed to provide heat during cloudy hours or when the sun sets. This study therefore focuses on an indirect solar dryer to identify the best location for a storage unit. Three cases were examined through numerical simulations using ANSYS Fluent, which were validated experimentally: The first case is where the PCM is located under the absorber plate, the second case is where the PCM is located in the plenum, and the third case is where there is no PCM. In order to make this comparison fair, we respected the same amount of PCM in both cases. The results show that the first case outperforms the second in terms of the average temperature inside the drying chamber. However, beyond 8 p.m., the opposite is observed, with the maximum temperature difference from the case without PCM reaching 9 and 8° for the first and second cases respectively. As regards air uniformity, the second case made the air more uniform along the trays compared with the other cases.