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In the current design, we have two circular orifices on the same pipe segment.  Originally, the micro-mixing orifice was after the first pipe bend.  However we have decided to change that to allow facility of removal when cleaning is required.  The micro-mixing orifice is two pipe diameters below the macro-mixing orifice.  This ensures adequate mixing time for macro-mixing to take effect.  The orifices for both equations are sized using the equations of minor loss coefficient for a submerged orifice. 
Image Modified
 
Where:
 
K.e.orifice:   Minor loss coefficient
K.vc:  Vena contracta coefficient
d.pipe:  Pipe Inner Diameter
d.orifice:  Diameter of orifice

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Research has estimated that for a macro-mixing orifice, we should have   a minor loss coefficient of 1.3.  This is what we are using for our design.  In the case of the micro-mixing orifice, we should strive for an energy dissipation rate of 1 W/kg.  In the future we plan to use the micro-mixing orifice as a flow measurement device and allow thus when sizing the orifice we need to have a head loss of 20 -to 50 cm .  From here, we derive the orifice sizeat maximum flow rate. 

In the case of a macro-mixing orifice, each pipe diameter allows for one orifice size.  An increase in flow-rates will give the macro-mixing orifice a significant head loss.  In the algorithm, if there is significant head loss (2 cm or above), then the piping is upgraded to the next size. 

The algorithm can be summarized in these following steps:

• Determine the inner pipe size given the flow-rates, maximum pressure drop (20 to 50 cm). total minor loss coefficients, and the available pipe sizes. 
•  Using the pipe size given, determine the orifice diameter of the macro-mixing orifice.  This is determined using the equation for minor loss coefficients for submerged orifices
• If the head loss through the macro-mixing orifice exceeds 2 cm, then move up to the next pipe available and recalculate the orifice size.  This step is repeated until the head loss is 2 cm or less. 
• Use the assigned total head loss value (20-50 cm) and maximum flow rate to determine the minor loss coefficient needed for the micro-mixing orifice.  Using the equation for minor loss coefficients for submerged orifices to determine the orifice diameter for the micro-mixing orifice.

There will be changes made to make this algorithm more robust and they are in process.