Modelling and analysis of flat plate solar air collector with phase change materials for extended surface, drying application

This study explores the design and thermal performance of a flat plate solar air collector integrated with a phase change material-based thermal energy storage unit and cylindrical aluminum fins, developed to enhance the efficiency of agricultural drying. Conventional solar dryers often struggle with inconsistent drying due to intermittent solar radiation and inadequate thermal storage. To overcome these challenges, the FPSAC includes a 1.57 m² absorber surface, covered with 5 mm low-iron tempered glass to maximize solar transmittance and insulated with 25 mm of rock wool to reduce heat loss. Paraffin wax RT50, with a melting point around 50 °C and a latent heat of 170 kJ/kg, was selected as the PCM for its ability to store medium-range thermal energy. The TES unit, measuring 0.5 × 0.25 × 0.45 m, holds 48 kg of PCM and can store up to 8.16 MJ of energy. Inside the PCM, 32 aluminum fins (100 mm in diameter and 1200 mm in length) are embedded to improve thermal conductivity and promote even heat distribution during both the charging and discharging phases. Numerical simulations conducted using ANSYS Fluent 19.2 and COMSOL Multiphysics 6.3, based on an average solar radiation of 800 W/m² in Addis Ababa, indicate that the system can achieve an outlet air temperature of 45.6 °C and deliver up to 1.27 MJ of thermal energy after sunset extending drying time by over 70 min beyond daylight hours. The fins play a crucial role in accelerating the melting and solidification of the PCM, improving the thermal responsiveness and efficiency of the system. Overall, the results suggest that this FPSAC-PCM system is a practical, cost-effective, and sustainable solution for agricultural drying and food preservation in regions with fluctuating solar conditions.