Theoretical and experimental analyses of drop deformation and break-up in a scale model of a high-pressure homogenizer

High-pressure homogenizers (HPHs) are used to create sub-micron emulsions in low-viscosity fluids. As the flow in a real HPH is very extreme, with gaps ranging from 10 to 100 μm and high velocities, it is almost impossible to visualize the drop break-up process. In this study a plastic scale model of a HPH was made, allowing the visualization of drop deformation and break-up. Great care was taken to keep the relevant dimensionless numbers constant during the scaling-up. The experimental data were interpreted in terms of theoretical drop break-up theory. It was found that both viscous and inviscid mechanisms can deform the drop. When a drop is exposed to a high-energy eddy, the deformation process proceeds rapidly. The deformed drop offers very little resistance to the eddies surrounding it, and it is drawn out, coiled and finally broken up into smaller droplets of various sizes.