Cavitation in a pump occurs when the absolute pressure at the eye of the impelle

Question

Cavitation in a pump occurs when the absolute pressure at the eye of the impeller is greater than the vapor pressure of the fluid being pumped, causing the fluid to boil and form vapor bubbles. During cavitation, as the bubbles that form move into a zone of higher pressure, they collapse and the surrounding fluid rushes violently to fill the void, producing a hammering action that can cause vibration and pitting of the pump impeller. The net positive suction head (NPSH) is the total absolute head above the vapor pressure of the fluid at the eye of the impeller. Two equal pumps operating is series will double the discharge. Two equal pumps operating in parallel will double the pressure. Fundamentally, the operation of a centrifugal pump has the fluid entering at the eye of the impeller and being accelerated outward by the vanes of the rotating impeller, which increases the kinetic energy of the liquid. As the liquid exits the pump through the casing, the velocity decreases, converting kinetic energy (velocity head) to flow-work energy (pressure head). For a pump connecting equal diameter pipes, its net effect is to increase pressure in the pipeline. Static lift is the elevation difference, which a pump must raise the fluid being pumped. If the downstream point (Z_1) is at a lower elevation the upstream point (Z0. there is no static lit and the pump must only overcome the dynamic lift, which includes friction and minor of energy. When a storm sewer pressurizes, the EGL is indicated by the water level in a manhole, which is above the crown of the downstream pipe. When a culvert pressurizes, the headwater at the inlet is above the crown of the downstream pipe. Open channel flows are classified as subcritical, critical, or supercritical by comparing the actual depth of flow with the uniform (normal) depth of flow.

Explanation / Answer

A. (T)

B.(T)

C.(T)

D.(F)

E.(T)

F.(F)

G.(F)

H.(G)

Reason: -

In D part ..discharge will be double but pressure will remain same ( Not doubled).

In last part (H) the open channel is categorized on the basis of foude No or critical depth .

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