Simulation of airflow inside greenhouse solar dryers for Isfahan climate

Greenhouse drying is one of the drying methods that can dry large amounts of agricultural products simultaneously. All greenhouse dryer models use solar radiation energy. Greenhouse dryers are very similar in appearance to a greenhouse in that the air inside is  heated by solar radiation, and the desiccants are dried inside. Because a large part of Isfahan province has a dry climate and has 300 sunny days a year, there is a high potential for using this type of dryer. The performance of this dryer depends on the airflow characteristics and the geometry of the dryer chamber. Therefore, this study aims to predict the behavior of airflow inside the chamber of greenhouse dryers using computational fluid dynamics (CFD) for the climate of Isfahan. For this purpose, the effect of sunlight intensity and external geometry of the dryer on the speed, temperature, and air pressure inside the chamber was investigated by Ansys Fluent 18 software. This study evaluated four common types of geometries for greenhouse dryers. These four types of geometry include a greenhouse with a convex roof, a one-sided sloping roof, a double-sided sloping roof, and a greenhouse with a convex roof and vertical walls, respectively. The simulation results were validated by comparison with experimental results obtained from other researchers. The results showed that the greenhouse with a convex roof and vertical walls had the best performance in the uniformity of airflow velocity inside the dryer. Also, the best performance in the uniform air temperature distribution inside the dryer was related to the double-sided sloping roof and the greenhouse with a convex roof and vertical walls. The lowest air pressure inside the dryer chamber was associated with the geometry of the greenhouse with the convex roof.