Enhanced Agricultural Drying using Evacuated Tube Solar Dryer with Tri-Hybrid Nanofluids and PCM Heat Storage

An evacuated tube solar collector (ETSC) integrated with a solar dryer provides an effective approach for utilizing solar energy to dry agricultural product supporting sustainable development in India. This study aims to evaluate the overall thermal and drying performance of an ETSC system by testing a tri-hybrid nanofluid through aluminium oxide (Al₂O₃), multiwalled carbon nanotubes (MWCNT), and iron oxide (Fe₃O₄) blended in a 40:30:30 ratio with water at varying weight fractions of 0.5 wt%, 1 wt%, and 1.5 wt%. Also, the copper coil with paraffin wax phase change material (PCM) was incorporated into the heat exchanger to maintain a consistent heat supply to the dryer. Moreover, the red Chilli was used as a test product to analyse moisture content reductions and drying efficiency. The experimental result indicates that the 1.5 wt% tri-hybrid nanofluid exhibited superior thermal performance, which could achieve a maximum heat gain of 576.4 W, thermal efficiency of 77.5%, and exergy efficiency of 13.6%. Correspondingly, the dryer attained a reduced moisture content of 38.6% and the highest drying efficiency of 46.2%. These improvements were attributed to the synergistic heat transfer and energy absorption properties of the tri-hybrid nanofluid combined with the phase change material heat exchanger, demonstrating an effective strategy for enhancing evacuated tube solar collector -based solar drying.