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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 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 above a certain limitation (2 cm or above), then the piping is upgraded to the next size. There were plans to use the micro-mixing losses for flow measurement and due to this it was thought that there should be a constraint on the head loss through the micro mixerWe want to keep the head loss through the rapid mixer at 20 - 50 cm maximum and prefer that most of this head loss can be given to the micro-mixing orifice. To accomplish this, the pipe sizing algorithm is modified to select pipe sizes that will meet this constraint. Another assumption is that the head losses through the entire plant (both micro-mixer and macro-mixer as well as flocculator) would be used to measure flow. Due to this, this algorithm will be set to allow the user to determine the constraint, if any they would like to put on the macro-mixer head. Having little or no constraints will allow for smaller pipe sizes.
The equation for head loss is shown below:
Where:
h: Head Loss
K: Minor Loss Coefficient
V: Velocity of Fluid
G: Gravitational Constant
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Running this algorithm for flow-rates under 50 L/s gave the following results as shown below on Figure 2.
Figure 2:
Figure 2: Rapid Mix Orifice Sizing Algorithm for Lower Flow RatesRapid mix sizing algorithm for lower flow rates with 50 cm maximum head loss and 2 cm constraint on macro-mixer
We also did runs where the constraint was raised to 10 cm head loss through the maco-mixing orifice.
Figure 3: Rapid mix sizing algorithm for lower flow rates with 50 cm maximum head loss and 10 cm constraint on macro-mixer
With this lower constraint, we find much smaller pipe sizes used. The micro-mixing orifices are also larger. We can also change the results to see what happens when we want a 20 cm head loss through the rapid mixer with our 2 cm constraint through the macro-mixer.
Figure 4: Rapid mix sizing algorithm for lower flow rates with 20 cm maximum head loss and 2 cm constraint on macro-mixer
The results for the pipe sizing and and macro-mixer sizing are not changed but we have larger orifices.
The current work is now coding this onto the AutoCAD along with entrance tank.