Flow Conditions in the Disruption System

Generally, a laminar flow is found after the high-pressure pump. Due to the reduction of the cross-sectional area in front of a disruption system, the stream is accelerated and elongated, which results in elongational and shear stresses. From a critical homogenization pressure, the stream detaches on the inlet edge and thus produces the first depression area. In this depression area, cavitation may occur. Furthermore, the detaching of the flow depicts the instability in the stream and may also induce a turbulent transition or a back flow area. Inside the hole, the core of the stream stays laminar, but on the boundaries first eddies can rise. 

Geometric parameters influence local flow conditions. In flat valves, as designed to date, the inlet edge has no 90° but rather around 45°. This extends the time of the elongational flow in the inlet and reduces the effects of the detaching on the 

2 Effect of Flow Conditions in Homogenization Valves on Emulsion Droplets 

Droplets are deformed and disrupted by tensions, which result from different flow conditions and act on their interfaces. The high-pressure disruption system creates the required local flow conditions. The resulting flow conditions also depend on the emulsion s material parameters like the viscosity of the phases or the viscosity ratio between droplets and continuous phase, respectively [19, 21]. Laminar shear flow, elongational flow, as well as the turbulent flow and cavitation-induced microturbulences are usually found in industrial homogenization valves. 

Cavitation is a huge challenge for the service life of homogenization system due to the abrasion induced, but is also effective in disrupting emulsion droplets. 

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