Modeling the performance of the reversed absorber with packed bed thermal storage natural convection solar crop dryer

A transient analytical model has been presented to study the new concept of a solar crop dryer having reversed absorber plate type collector and thermal storage with natural airflow. The performance of 1 × 1 m2 area of crop dryer with packed bed and airflow channel was evaluated for drying of onions. The model was solved to compute the air temperatures and various functional components of the drying systems for a day of the month of October for the climatic condition of Delhi (India). The parametric study involved the effect of width of airflow channel and height of packed bed on the crop temperature. The effect of thermal storage is observed on the natural mass flow rate in the drying system. A 30° inclined absorber plate with in-built thermal storage and 0.12 m width of airflow channel induced the mass flow rate in the range of 0.032–0.046 kg s−1 during the drying process. The thin layer drying equation was used to study the drying rate and hourly reduction in moisture content in the crop trays. It has been observed that the crop moisture content and drying rate decreases with the drying time of the day. A reversed absorber plate of 1 m length and 1 m breadth with 0.15 m packed bed could dry 95 kg of onion from a moisture content of 6.14–0.27 kg water/kg of dry matter in a 24 h drying period.