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Research has estimated that for a macro-mixing orifice, we should have 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 thus when sizing the orifice we need to have a head loss of 20 to 50 cm at 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 reason for having a minimum flow-rate for macro-mixing is that we plan to use the macro-mixing orifice as a flow-measurement device which can handle 20-50 cm maximum head loss at maximum flow-rate. The micro-mixing orifice is sized for a minor loss coefficient that allows for this type of flow and head loss. The equation for minor loss coefficients for a submerged orifice shown above is used to find the orifice diameter needed.
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.
For a flow rate of 1 L/s with 50 cm maximum head loss, we obtained an inner pipe diameter of 1.89 in and macro-mixing and micro-mixing orifice diameters of 1.64 in and 0.94 in respectively. For the case of 2 L/s with 50-cm maximum head loss, we obtained an inner pipe diameter of 2.80 in and macro-mixing and micro-mixing diameters of 2.42 in and 1.33 in respectively.There will be changes made to make this algorithm more robust and they are in process.