The volute in a pump serves to do what to the cross-sectional area along the flow path?

The volute in a pump serves to do what to the cross-sectional area along the flow path?

• A. Increase toward discharge
• B. Decrease toward discharge
• C. Remain constant
• D. Vary unpredictably

Answer: (A)

The volute is designed to slow the fluid and convert kinetic energy into pressure as it moves toward the discharge. Since the flow rate is essentially constant, increasing cross-sectional area along the flow path causes the velocity to decrease (v = Q/A). Slower velocity at the discharge means higher static pressure, helping to develop the pump head and smooth the flow from the impeller into the outlet. The spiral shape also helps distribute flow evenly and minimizes abrupt losses. If the area were to decrease toward discharge, velocity would rise, increasing losses and reducing pressure gain; a constant area wouldn’t optimize energy conversion; and varying unpredictably would make performance unstable. Hence the area increases toward discharge.

The volute is designed to slow the fluid and convert kinetic energy into pressure as it moves toward the discharge. Since the flow rate is essentially constant, increasing cross-sectional area along the flow path causes the velocity to decrease (v = Q/A). Slower velocity at the discharge means higher static pressure, helping to develop the pump head and smooth the flow from the impeller into the outlet. The spiral shape also helps distribute flow evenly and minimizes abrupt losses.

If the area were to decrease toward discharge, velocity would rise, increasing losses and reducing pressure gain; a constant area wouldn’t optimize energy conversion; and varying unpredictably would make performance unstable. Hence the area increases toward discharge.