Study of Internal Flow and Emulsification Process in a Homogenizer

The pressure homogenizer is extensively used to emulsify, disperse the products in various industrial fields including: food, chemical, pharmaceutical and biotechnology. The homogenizer basically consists of a high-pressure plunger pump usually with triple plungers to minimize pressure fluctuations and a homogenizing valve with a narrow gap. The homogenizing valve consists of a valve, valve seat and impact ring. The homogenizer exerts effects, such as a shear, an impingement, and a cavitation to fluid momentarily. The relatively large polydisperse oil globules of a coarse oil-in-water emulsion are subdivided into a large number of smaller globules in a narrow size range by a homogenizer. However, the flow within the homogenizing valve is not clarified theoretically. Therefore the action of a high-pressure, radial-flow homogenizer in breaking up the internal phase of oil drops in a coarse emulsion was investigated theoretically and experimentally. If the flow pattern within the homogenizing valve could be solved, a more efficient and stabilized emulsification could be carried out. In this paper, the influence of shape modification of the homogenizing valve was investigated in the emulsification action. The experiments using a small homogenizer are conducted and the experimental results were compared with the numerical simulation results. In short, we compared the calculated flow pattern (velocity distributions, pressure distributions, shear stress) with the drop size distribution result obtained in the experiment, and investigated the relation between the flow and the emulsification action in the homogenizing valve. In this experiment, two valve types (Sharp type and Flat type) were applied. In the experiment, the pressure drop in the valve, the distance from a valve outlet to an impact ring and the parallel gap part length were changed. The flow patterns were investigated using a Computational Fluid Dynamic model of the flow in the homogenizing valve. Here, a k-ε turbulent model was used for the modeling of the flow in the homogenizing valve. The flow in the homogenizing valve was calculated as a two-dimensional axisymmetric flow. The purpose of this paper is to clarify the effects of differences in the shapes of valves on the results of emulsification through the above experiments and numerical simulations.