Investigation of uniformity in multi-tray heat pump-hybrid air dryer system: Numerical modeling and experimental analysis

• Explored HPHAD with uniform inlet air velocity. • Optimized airflow improves drying uniformity in multi-tray HPHAD systems. • Investigated tray-sample positioning effect on drying uniformity. • Significant drying rate disparities were observed among different trays. Existing research primarily focuses on single-layer dryers due to their better airflow, whereas multilayer dryers encounter challenges with inconsistent airflow, temperature, and humidity levels. This study investigates the non-uniform drying kinetics across the trays in hybrid heat pump hot air drying (HPHAD) systems, highlighting the influence of airflow distribution on moisture concentration, temperature, and deformation in a multi-tray multi-sample configuration. The impact of airflow distribution on the performance of a multi-tray drying chamber were analyzed. A series of experimental investigations were conducted on mushroom dying using a multi-tray multi-sample configuration, coupled with simulated airflow and temperature conditions, at 50 °C and 60 °C with an air velocity of 1 m/s over a drying time of 300 min. The results revealed that tray 1 exhibited a drying rate 1.09 times higher than trays 2 and 4, and 1.2 times higher than tray 3. Discrepancies in uniformity were observed across sample positions, with moisture removal rates of 90.47 %, 87.90 %, and 86.65 % for selected samples in the same tray at 180 min. This study uniquely identifies and quantifies the challenges associated with airflow distribution in multilayer configurations, emphasizing the necessity for optimization by ensuring uniform inlet airflow at different trays. The findings lay a robust foundation for designing and operating energy-efficient multilayer drying systems. Future research should prioritize refining airflow and temperature optimization techniques and developing advanced simulation models for scalable industrial applications, to enhance drying uniformity, operational efficiency, and sustainability.