...
A pipe size/macro-mixing combination can be used for a range of flowrates. An increase in flowrates will result in a higher head loss for the macro-mixing orifice. This can actually result in the macro-mixing orifice having a higher head loss than the micro-mixing orifice. Due to this, the user can select a constraint value for head loss (usually 2 to 10 cm, currently set at 5 cm) that will cap how high the macro-mixing head loss can be. This is done by selecting a larger pipe size and larger macro-mixing orifice. In figure 2, the results for head loss through the macro-mixer are shown below. At high flow-rates, macro-mixing head loss becomes higher than micro-mixing head loss.
With the head loss of the entire plant and the entire system accounted for the constraint on the macromixer headloss (MacroMHConstraint = 5 cm) the size of the nominal diameter of the pipe, the diameter of the macromix orifice and the size and number of micromix orifices can be determined.
Figure 2: Rapid mix sizing algorithm for lower flow rates with 20 cm through micro-mixer and no constraints
...