VELOCITY MEASUREMENTS OF TURBULENT TWO-PHASE FLOW IN A HIGH-PRESSURE HOMOGENIZER MODEL

Abstract

The effect of disperse phase volume fraction on the turbulence in a scale model of a high-pressure homogenizer was studied experimentally. Velocity fields of the continuous phase were measured using particle image velocimetry. Refractive index matching combined with digital filtering enabled measurement with disperse phase present. Geometry and physical properties were carefully scaled in order to ensure turbulent flow and disperse phase modulation comparable to that of a technical high-pressure homogenizer. The results show a widening of the jet downstream of the gap and increased Reynolds stresses in the region of high turbulence intensity. This is consistent with previous experiments under similar conditions. Furthermore, the spectra of turbulent kinetic energy were investigated, indicating that the increase in turbulent kinetic energy is mainly due to an increase in energy of eddies of large length scales.

Keywords:

• Emulsification
• High-pressure homogenization
• Multiphase flows
• Particle image velocimetry
• Turbulence

Acknowledgments

This study was financed by the Swedish Research Council (VR). We would also like to thank Tetra Pak Processing Systems for supplying equipment and Mr. Göran Pantzar for aid in setting up the feedback control and flow loop system.

Notes

^a Properties of homogenizers from Innings (2005).

^b Measured density of sugar-salt solution.

^c Calculated based on porous silica gel particle with continuous phase in the pores.

^d Measured viscosity at operating temperature.

^e Measured Sauter mean diameter (microscopy); see Figure 4. 230 ± 76 µm (N = 110).

^f See Table II.