Turmeric (Curcuma longa L.) drying in a phase change material based solar drying unit with variable tilt angle solar air heater

Abstract

Solar dryers with thermal energy storage units emerge as the best solution for heating and drying purposes, especially during off-sunshine hours or overcast weather. This study introduces a Mixed Mode Solar Dryer (MMSD) enhanced with phase change material (PCM) to extend operational time. A Double Pass Solar Air Heater (DPSAH) is integrated with the dryer to optimize solar insolation collection, adjustable at various angles. The research enhances DPSAH efficiency by testing it at different tilt angles (17°, 22°, 27°, 32°, and 37°), varying airflow rates (0.0166 and 0.0217 m/s), and introducing wire meshes to obstruct airflow within the collector. After determining the optimal tilt angle and airflow rate, the dryer performance is evaluated by drying turmeric. The turmeric is dried from 84.2% moisture to 10.1% in 22.5 h, reducing drying time by 26.5 h compared to open sun drying (OSD). The average cabinet temperature of the dryer remains 19.41 °C higher than the ambient temperature, demonstrating effective heating. With an average efficiency of 49.28%, the DPSAH proves its effectiveness. This dryer is promising, especially in northeastern India, known for spices like turmeric, significantly reducing drying time and benefiting local economies.