Spray drying operations can be used to turn products, like for example milk or yeast extract, into powders, extending their shelf life. The properties of those powders (e.g. density or particle size) after spray drying operations depend severely on the dynamics of droplet collisi
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Spray drying operations can be used to turn products, like for example milk or yeast extract, into powders, extending their shelf life. The properties of those powders (e.g. density or particle size) after spray drying operations depend severely on the dynamics of droplet collisions inside the spray. Currently, costly and wasteful productiontrials are used in the spray drying industry. The use of computer models can potentially reduce those costs significantly. However, presentday models lack a complete physical foundation to supersede these trialanderror tests. This study aims to further develop implementation of the relevant physical processes in these models by incorporating the combined effect of rheology and surface tension. In this thesis, we quantify the effect of Particle Interaction Forces (PIF) on the surface tension and investigate the possibility to further calibrate the PIF induced surface tension to match the desired surface tension. Important here is that we do not change the PIF induced rheology. We make use of the numerical method Smoothed Particle Hydrodynamics (SPH) and use the Continuum Surface Force (CSF) method to further tune the surface tension. We demonstrate the tuning properties of CSF in a static and a dynamic setting. Because the constitutive equation of the PIF induced rheology is unknown, we are limited in the possible dynamic tests in which we assess the relation between the rheology and surface tension. The dynamic tests that we could perform in this thesis are characterized by the surface tension being dominant with respect to the viscosity and elasticity of the droplet. In the static case, we found that we can estimate the magnitude of the PIF induced surface tension and increase the surface tension with CSF to the desired value. Furthermore, for the static case, when both CSF and PIF are used, the total surface tension is simply the sum of the separate forces, i.e. CSF and PIF are decoupled forces. Additionally, preliminary results suggest that we can also lower the PIF induced surface tension to a certain extent, by adding CSF with a negative coefficient. However, the dynamic test results are not straightforwardly interpreted, probably due to not satisfying the assumption that the surface tension is the dominant contribution. Therefore, these tests are inconclusive and thus require further research.
