Study on volumetric heat and mass transfer coefficient in a spray drying process utilizing pressure swirl nozzle: A numerical and experimental approach

Abstract

This paper applies a sectional and cumulative approach to estimate the volumetric heat and mass transfer coefficients (hV and kV) to characterize the behaviour of the spray drying process. The investigation utilizes a tailor-made spray dryer equipped with a pressure swirl nozzle with a 0.2 mm orifice diameter, utilizing Mannitol solution as the precursor and air as the carrier gas. A comprehensive numerical analysis is conducted using the Adaptive Mesh Refinement (AMR) technique alongside selective experiments. The study considers precursor mass flow rates of 1 g/s, 1.2 g/s, and 1.5 g/s, along with carrier gas velocities of 0.88 m/s and 1.19 m/s at a temperature of 250 °C. Comparisons between predicted and estimated hV and kV are performed, leading to the proposal of a method for identifying constant rate and falling rate periods. The analyses contribute to delineating the solvent evaporation zone, solid particles heating zone, spray penetration length, and drying length. Additionally, experimental temperature measurements in both axial and radial directions at 12 grid points in the chamber are conducted to validate the numerical results, showing acceptable deviation.