Improving the thermal efficiency of a solar dryer using phase change materials at different position in the collector

Low thermal efficiency is one of the main problems in using solar collectors in different fields. In the present study, the effect of using phase change materials (PCM) inside the Flat plate collector (FPC) on the thermal performance and overall drying efficiency of FPC was investigated. Four PCM positions were considered inside of the collector, and the results compared with the collector without PCM. Experimental results implied that specific energy consumption for drying tomato slices is between 11.12 and 9.01 MJ/kg. The drying time of the slices using the collector with PCM at the end section was decreased about 21.87%. Based on the position of PCM, the thermal efficiency of FPC increased by about 5.02%-10.13%. The overall efficiency varied from 21.92% to 25.72% for different PCM positions. CFD simulation of the system was performed by Ansys 2015, and it showed that the thermal performance of the collector could be predicted with good accuracy (R2 > 0.9432). Moreover, the result of evolutionary polynomial regression models applied for each PCM position. It confirmed that outlet temperature and thermal efficiency of collector predicted with acceptable accuracy (R2 > 0.98). Due to the use of PCM at the end section of the collector, a homogeneous drying process, normal temperature, and short drying time resulted. The quality of tomato slices dried by the solar dryer was higher than other positions.