ANS:A -

Specific speed (NsN_sNs​) for a centrifugal pump is a dimensionless parameter that helps in characterizing the performance of the pump. It is defined as: Ns=NQH3/4N_s = \frac{N \sqrt{Q}}{H^{3/4}}Ns​=H3/4NQ​​ where:

• NNN is the rotational speed of the pump (in revolutions per minute, rpm),
• QQQ is the flow rate or discharge (in cubic meters per second, m3^33/s),
• HHH is the total head developed by the pump (in meters, m).

Interpretation:

1. Purpose of Specific Speed:
   • Specific speed is used to classify centrifugal pumps based on their geometric similarity and performance characteristics.
   • It helps in selecting or designing pumps for specific applications based on their operating conditions.
2. Relationships:
   • Higher specific speed (NsN_sNs​) indicates a pump that is better suited for higher flow rates and lower heads.
   • Lower specific speed indicates a pump that is better suited for lower flow rates and higher heads.
3. Typical Ranges:
   • Low specific speed (less than 500): Pumps for high head applications (e.g., boiler feed pumps).
   • Medium specific speed (500-3000): Pumps for general-purpose applications (e.g., water supply pumps).
   • High specific speed (greater than 3000): Pumps for low head, high flow applications (e.g., sewage pumps).

Conclusion: