Flow studies in an in-line Silverson 150/250 high shear mixer using PIV

Angle resolved 2-D PIV measurements were taken of the flow inside an in-line Silverson 150/250 high shear mixer, facilitated by a custom built transparent poly methyl methacrylate mixing head. Water was used as the working fluid in the turbulent regime (120,000 < Re < 420,000) and measurements were taken in a field of view encompassing one quarter of the whole mixing head. The effect of the presence of an additional externally driven flow from a pump, and back pressure using an outlet control valve, were examined. The results show that the dominant flow pattern can either be radial or tangential with the former being driven by the external flow at high flow rates and the latter at increasing rotor speeds. Increasing the back pressure promoted tangential flow. Detailed measurements were made of the influence of these parameters upon the mixer flow pattern and calculation of flow number from 2-D PIV data; the latter are strongly influenced by the geometry of the mixer and pipework.