Effect of inserting a thermal packed bed under a solar air heater for drying applications

One of the major problems facing solar dryers is the drop in temperature at night when the sun sets. Therefore, one of the simplest and most economical ways to provide heat at this time is to insert a storage unit that stores thermal heat during the sunny hours of the day and releases this energy at night. In this article, a storage unit is inserted under the absorber plate of a solar air heater which is the main component of a solar dryer. The storage unit is in form of a packed bed which is simulated as a porous medium of pebbles. The effect of using this packed bed is studied under the real climate of Oujda city (Morocco) using ANSYS Fluent software. In addition, the effect of its thickness as well as different pebble materials are studied under natural convection. The findings showed that a 10 cm gravel packed bed is suitable for drying applications.