Indirect solar dryer with enhanced phase change materials and modified air heating system: A state-of-the-art review

Abstract

This review provides a comprehensive evaluation of recent advancements in indirect solar dryers, focusing on the integration of advanced phase change materials (PCMs) and improved air heating mechanisms with computational fluid dynamics. Nanoparticle-enhanced PCMs, encapsulation techniques, and fin-inserted PCM composite compounds are extensively examined for their roles in boosting thermal conductivity, latent heat storage capacity, and temperature regulation during drying processes. Meanwhile, enhancements in air heating setups, such as double-pass solar collectors, finned absorbers, and hybrid modules, are evaluated for their impacts on drying kinetics, airflow consistency, and overall energy efficiency. Indirect solar drying technologies are gaining more attention due to their ability to improve food preservation and reduce post-harvest losses through renewable energy use. To identify design strategies that enhance thermal efficiency, drying speed, and product quality, the relationship between PCM placement, airflow behavior, and dryer shape is examined. Despite noteworthy progress, some issues remain, including material degradation, cost-effectiveness concerns, and barriers to widespread adoption. To support real-world implementation, the paper highlights the importance of developing adaptive control systems, such as photovoltaic-thermal (PVT) modules, and conducting comprehensive techno-economic analyses. This work lays a foundation for creating high-performance solar drying solutions that are adaptable to various crop types, operational requirements, and climate conditions by combining current knowledge and pinpointing key research gaps. The findings aim to direct future research and innovations toward more efficient, scalable, and sustainable solar drying methods supported with computational fluid dynamics. • A comprehensive evaluation of recent advancements in indirect solar dryers was conducted. • Nanoparticle-enhanced PCMs, encapsulation techniques, and fin-inserted PCM composite compounds are extensively examined. • This work lays a foundation for creating high-performance solar drying solutions. • Solar drying methods supported with computational fluid dynamics were evaluated.