Thermo-kinetic behavior of closed-loop heat pump dryer with different drying chambers for holy basil leaves drying application: an experiment approach

A closed-loop heat pump drier was designed and constructed with three different drying chambers (tray, fluidized bed, and integrated) to investigate the drying kinetics (drying rate and specific moisture evaporation rate) of holy basil leaves in this research work. The significance of drying temperature, air velocity, and mass of leaves on the performance of the dryer chambers was explored and compared through an experimental investigation. In addition, the present research focuses on analyzing the significance of drying air temperature (45, 50, and 55°C), air velocity (1.5, 2.0, and 2.5 m/s), and mass of holy basil leaves (5, 6, and 7 kg) on the performance of the dryer chambers. In tested combinations, the specific moisture evaporation rate and drying rate are higher in the integrated drying chamber. Notably, the effective moisture diffusivity coefficient exhibited a range of values from 2.68166 × 10⁻¹⁰ to 6.10243 × 10⁻¹⁰ m²/s. The design of the experiment approach is applied to optimize the number of experiments, and an analysis of variance was conducted to identify the most influential parameter. The results showed that temperature had a greater effect, accounting for 32% of the variation in the moisture evaporation rate.