I am working on a scale-up solution for my laboratory from bench chemistry mixing techniques (in volumetric flasks) to industrial mixing protocols in a 60L stirred tank. The current application involves manufacturing a solvent matrix of two low-viscosity liquids of similar density. Rayleigh numbers show that the flow dynamics are in the turbulent regime.

Before I came on to the project they had already designed high aspect ratio 2.5 H x 1 D cylindrical tanks without baffles, and currently they have ordered one 45 deg. pitched blade impeller. I believe I have justified adding two more strategically spaced turbines to the impeller shaft, but I am also trying to justify a redesign of the tanks with four standard 1/12 D baffles. I have explained the problematic swirling flow issues that arise when mixing in unbaffled tanks in the turbulent regime, but the main concern for the decision-makers is "to what degree would adding baffles reduce blend time."

I have worked up a solution to this, however, since these are miscible liquids with very high Rayleigh numbers, the blend time improvements are negligible from a cost/benefit perspective. I want to direct their focus to the product validation concerns.

It is my theoretical understanding that the regions within the tank that have undesirable flow dynamics will make it difficult for us to achieve high levels of certainty that the entire batch is well-mixed enough for each sample to be homogenous even after adjusting the model to allow for very long blend times. We need each 50 ml sample of the 36L matrix to be analytically verifiable at the correct solvent ratio.

Is anything in the literature that supports this theory that complete mixing to this level of accuracy (99.95%) is virtually impossible to achieve without adding baffles to the tank (particularly with a single turbine impeller in an unusually high aspect ratio tank)?