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Pipeline mixing of different phases/species in many chemical processes can be achieved by a variety of approaches. Whether mixing hot and cold streams in a nuclear installation or solvent and bitumen streams at an oil sands mine, the goal is often the same—achieving optimal homogeneity.

One of the simplest approaches is to introduce the second stream via a T-junction (jet in cross-flow) and rely on turbulence to mix the streams. An alternative approach is to use a mixer to achieve faster and more efficient blending, but at a cost of a higher pressure loss.

The degree of mixing non-uniformity is commonly quantified by the Coefficient of Variation (CoV), defined as the ratio of the standard deviation to the mean value of the component concentration. A CoV value of zero means the system has achieved homogeneity.

Turbulent mixing of two streams of water in a T-junction is shown in the plot. The flow pathlines, colored by temperature contours, qualitatively compare the degree of mixing between the two cases. In the baseline case, thermal mixing is achieved through pipe turbulence, while the second case uses a Kenics-type static mixer downstream of the T-junction. The intense mixing of the two streams as they pass through the static mixer is evident in the CoV plot.

CFD simulations can be used to determine flow conditions and blending performance for an existing design of a mixing system, to screen and evaluate alternative designs, and to arrive at an optimum performance of the system within specific operational requirements. Coanda has helped many clients in assessing the mixing performance of their system/processes by utilizing CFD models validated via experimental measurements.