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Impeller Flow
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This is a continuation of the Process Intensifier - Optimization with CFD: Part 1 paper.

Although the flow number, Nq, of the impellers could be determined using the CFD and integrating the velocities over the area of the impeller, it was not done in this study. We can estimate the flow number fairly well from the literature. The exact number is not important for this discussion, though. We assumed that Nq = 1.1 for each impeller in LTR and Nq = 1.2 for each impeller in HGR. We assumed Nq = 0.56 for the axial flow impellers.

1750 RPM

Radial Process Intensifier

Axial Process Intensifier

 

GPM (m3/s)

R650

R1100

GPM (m3/s)

R650

R1100

Lightnin

1042 (0.0657)

1.60

0.95

182 (0.0115)

0.28

0.17

Hayward Gordon

1136 (0.0717)

1.75

1.03

530 (0.0335)

0.82

0.48

Table 5: Estimated flow generated by the impellers in GPM (m3/s), and the ratios, R, of impeller flow to pipe flow rate (at 650 and 1100 GPM (at 148 m3/hr and 250 m3/hr)).

Table 5 is very interesting. As a rule-of-thumb for continuous processes, the impeller generated flow should be at least 3 times the throughput. As we can see here, not one of these devices complies. Even the LTA appears to be doing some mixing at 650 GPM, which has R = 28% or about 1/4th the pipe flow rate. LTA seems to have lost its mixing ability at 1100 GPM. Perhaps the rule-of-thumb for Process Intensifiers is that impeller generated flow should be at least 1/4th the pipe throughput.

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