Project ForgeFluid Mechanics
Mechanical Operations
GATE 2012
Medium
In a mixing tank operating at very high Reynolds number (>10⁴), if the diameter of the impeller is doubled (other conditions remaining constant), the power required increases by a factor of
- A1/32
- B1/4
- C4
- 32
Explanation
At high Reynolds number, the power number Np is constant, and P=Np·ρ·N³·D⁵. With rotational speed N held constant and D doubled, power increases by 2⁵=32.
Source: GATE CH 2012 (2012)
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