Optical Analysis of Liquid Mixing in a

Abstract: A novel optical sensor was used to study mixing and mean circulation time in a model minibio-reactor (12.5 mL stirred vessel, equipped with a paddle impeller). Rotational rates in the range of 10–1,000 rpm corresponding toReynolds number between 14 and 1,350 were studied. Results suggest that depending on the impeller rotational speed, mixing times up to 214 87 s can be reproducibly achieved. The minibioreactor was operated in the transitional regime, and itwas determined that the non-dimensional form for mixing time, NYMwas linearly dependent on Reynolds number. A linear correla-tion between mean circulation time and the inverse of rotational speed was also determined. The mean circula-tion time dependence on rotational speed in the 12.5 mL stirred vessel is similar to those found in large-scale stirred vessels. These results suggest that mixing and circulation times found in large-scale reactors can be replicated in minibioreactors. 2005 Wiley Periodicals, Inc