Question

If the value of Reynolds number \(>10000 \) for an impeller, the power number:

• A. Increases first and then decreases with an increase in impeller Reynolds number
• B. Increase with an increase in impeller Reynolds number
• C. Remains constant with an increase in impeller Reynolds number
• D. Decreases first and then increases with an increase in impeller Reynolds number

Hint:

When dealing with turbulent flow and Reynolds numbers greater than 10,000, remember that the power number typically stabilizes and does not change significantly with further increases in Reynolds number.

Answer 1

The Correct Option is C

For Reynolds numbers greater than 10,000, the flow generally becomes turbulent, and the power number tends to remain constant. This behavior occurs because, in this range, the flow regime is well established and independent of changes in Reynolds number. The power number is a dimensionless number that characterizes the power consumption of an impeller in turbulent flow.
- Option (1) Increases first and then decreases with an increase in impeller Reynolds number is incorrect because, for Reynolds numbers above 10,000, the power number does not follow this pattern.
- Option (2) Increase with an increase in impeller Reynolds number is incorrect, as the power number tends to remain constant rather than increase.
- Option (4) Decreases first and then increases with an increase in impeller Reynolds number is also incorrect since the power number remains constant in this Reynolds number range.
Thus, the correct answer is option (3): Remains constant with an increase in impeller Reynolds number.