Thermal Performance Analysis and Heat Transfer Characteristics of a Solar Powered Paddy Dryer Using a Flat Plate Solar Collector

Freshly harvested paddy holds much water (23.00% wet basis in this study) and spoils quickly without prompt drying. Open sun drying depends on the weather and heats the grain unevenly. This study tested an indirect solar paddy dryer with a 0.60 m² flat plate collector, a 10 kg capacity, and natural convection airflow in Merauke, South Papua. Six thermocouples (collector, drying chamber, and chimney), a pyranometer, and a moisture meter recorded data every 15 minutes at drying temperatures of 40°C, 50°C, and 60°C. The data gave useful heat energy, collector thermal efficiency, and drying rate. Useful heat energy ranged from 103.85 to 232.02 W (mean 182.69 W), and thermal efficiency ranged from 35.25% to 60.54% (mean 43.96%). Mean air temperature fell from 51.41°C at the collector outlet to 44.94°C in the drying chamber and 38.94°C at the chimney, which confirms the expected heat transfer gradient along the airflow path. Final moisture content reached 17.24%, 12.00%, and 10.11% at 40°C, 50°C, and 60°C, respectively. The highest drying rate (0.1560 %wb/min) and the best Page model fit occurred at 60°C. The dryer uses solar energy without electricity for air circulation, so it can support energy-efficient post-harvest handling in tropical climates