Abstract Summary (Max 250 words)
Whilst the fundamentals of conventional stirred tank mixing processes have received great attention over the last 70 years, there have been very few studies devoted to vibromixers – which mix with an oscillating plate – despite the fact that they have been applied in industry for over 30 years. Indeed, there is almost no fundamental knowledge of flow and mixing performance of vibromixers (particularly high-frequency/low-amplitude devices) documented in the literature. This work experimentally characterizes the hydrodynamics and mixing performance of a vibromixer, operating at 100 Hz and amplitudes of a few millimeters. Experiments have been performed with a Fundamix vibromixer with a perforated oscillating plate in a cylindrical dish-bottomed glass tank (T=0.15m, H=T). Several diameters of vibromixer plates (D/T=0.3–0.43) were used and at different off-bottom clearances (C/T=0.33–0.5). PIV was used to measure velocity fields and to estimate turbulence kinetic energy and shear rate. Power consumption was determined using a piezoelectric force sensor. Mixing time was evaluated using the coloration-decolorization technique. PIV results show the vibromixer creates one circulation loop similar to a rotating axial flow impeller in turbulent flow whilst shear rates are low (< 0.05 s-1). The power number follows a similar trend to conventional stirred tanks whereby it is constant in turbulent flow and inversely proportional to Reynolds number in laminar flow. However, specific power input is of the same order of magnitude or less than a stirred tank. Mixing times are short compared with a turbulent impeller stirred tank.
