Design and performance analysis of a new flat solar heating porous collector equipped with vertical copper pipe and porous medium for medicinal plant drying

A suitable technique for dehydrating crops, particularly medicinal plants, is to use a combination of independent solar systems under suitable economic conditions. In the present study, TeucriumpoliumL (TP) was dried using an indirect solar cabinet drier with a newly designed unglazed transpired solar collector equipped with chrome color porousmedium. TP samples were dried in a single layer and the experiments were carried out at two airflow speeds and compared with the samples dried in front of the Sun. Additionally, thermal behavior, temperature distribution (using computational fluid dynamics), exergy, and economic analyses were carried out for the unglazed transpired solar collector. The findings implied that the maximum temperature of the drying chamber for the fluid flow rates of 0.01 and 0.015 kg/s was obtained at 334.07K and 333.9K, respectively. The maximum outlet fluid temperature of the proposed collector was 341.8K, which was higher than the common with the airflow rate of 0.01 kg/s. The energy saving for the presented study was 70.53 %, which was higher than the solar systems with similar conditions. In addition, the highest collector efficiency of 45.92 % during the drying process was for the flow rate of 0.015 kg/s. The employed CFD model within reasonable bounds predicted the collector's thermal performance. The drying time of TP was in the range of 960–990 min, but it lasted for 3360 min with the open sun drying method. The dryer was optimized based on the applied conditions, and the results showed a reduction in the payback period. The Page model was the best to predict the drying process of TP.