ID 3

On SprayDry nozzle flow path effects on atomization and the influence of fluid viscosity

 

Abstract:

Spray dry nozzles represent a notable portion of industrial atomizers, and are typically used to generate a dried powder from a liquid or slurry. From a spray technology perspective, these nozzles are identified as pressure-swirl nozzles that operate at high pressures in order to generate relatively small droplets with controlled distributions. In this study, nozzles which are used for spray drying in areas such as the Dairy, Food, Pharmaceutical, and Chemical industries, are characterized and analyzed over a range of operating conditions. Parameters of interest include nozzle type (Swirlchamber, Whirlchamber, and Slotted Core) and material viscosity, where water-based mixtures with viscosities of 1, 1000, and 5000 cP are investigated. For the experiments, a Phase Doppler Interferometer instrument is used to acquire drop size, velocity, and concentration information, while the modeling effort was conducted using the ANSYS Fluent package. Traditionally difficult measurements due to high spray density, the detailed test results across each spray plume provide insight on the spray characteristics over the range of operating conditions. The detailed computational models of the internal flow paths of each nozzle type reveal upstream velocity characteristics which are responsible for generating the downstream spray characteristics. Greater understanding of the upstream flow characteristics, and downstream spray characteristics, allows for improved nozzle selection and design to achieve targeted performance, atomization, and efficiency.