Rate and time of mixing

In practice, the mixing time will be that recpiired for the mixture composition to come within a specified (95 or 99%) deviation from the equilibrium value Coo and this will be dependent upon the way in which the tracer is added and the location of the detector. It may therefore be desireable to record the tracer concentration at several locations, and to define the variance of concentration about the equilibrium value as  

For a given experiment and configuration, the mixing time will depend upon the process and operating variables as follows  

Using dimensional analysis, the functional relationship may be re-arranged as  

For geometrically similar systems and assuming that the Froude munber, Fr (= DN /g) is not important, 

Broadly speaking, the dimensionless mixing times in both the laminar and fully turbulent regions are independent of the Reynolds number a substantial transition zone exists between these two asymptotic values. Undoubtedly, the functional relationship between 9 and Re is strongly dependent on the mixer geometry and the flow patterns produced. 

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