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A bioreactor is scaled up based on equal impeller tip speed. Consider the following parameters for small and large bioreactors: ParametersSmall Large bioreactor bioreactor Impeller speed N1 N2 Diameter of impeller D1 D2 Power consumption P1 P2
Assuming geometrical similarity and the bioreactors are operated in turbulent regime, what will be P2 / P1?
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- (D1 / D2)2
- (D2 / D1)2
- (D1 / D2)5
- (D2 / D1)5
Correct Option: B
Scaled up criteria is equal to impeller tip speed
So N1 D1 = N2 D2
| ∴ | = | ...(i) | ||
| N1 | D2 |
Now, power equation is given by
P2 ∝ N23 D25
| = | = |  |  | 3 | | | 5 | |||||
| P1 | N13 D15 | N1 | D1 |
| = | | | 3 | | | 5 | | ∵ | = | | |||||
| D2 | D1 | N1 | D2 |
| = | | | 2 | |||
| P1 | D1 |
