Analysis of the flow field in a high-pressure homogenizer

Numerous theories have been developed describing the drop break-up in a high-pressure homogenizer (HPH), but they are generally based on quite rudimentary descriptions of the flow fields. As the flow in a real HPH is very extreme, with gaps of 10 - 100 mu m and velocities of hundreds of m/s, it is practically impossible to measure the velocity fields. In this study, a scale model of an HPH made of acrylic plastic has been developed making measurements possible. Great care was taken to keep the relevant dimensionless numbers constant during the scale-up. The flow field at the gap entrance shows a steady acceleration and total turbulence suppression, in the gap the flow field is flat with thin boundary layers, and at the exit a turbulent jet is formed. The jet was found to be very unsteady, and in very similar flow situations could either be attached to the walls or continue straight ahead after the gap. (c) 2007 Elsevier Inc. All rights reserved.