Find the Net Positive Suction Head NPSH in m Explain why a v

Find the Net Positive Suction Head (NPSH) in [m]. Explain why a very low NPSH is undesirable. How a low NPSH would affect the pump performance? Draw a neat sketch (do not calculate the points) of head versus flow rate (Q-H_p curve) for a gear pump. Equation NPSH = P_s/gamma + P_a/gamma - P_v/gamma + V_s^2/2g H_s = P_s/gamma + V_s^2/2g + Z_s H_d = P_d/gamma + V_d^2/2g + Z_d

Solution

When asked how a pump operates, most reply that it \'\'sucks\'\'::. While not a false statement, it’s easy to see why so many pump operators still struggle with pump problems.\"\" Fluid flows from areas of high pressure to areas of low pressure. Pumps operate by creating low pressure at the inlet which allows the liquid to be pushed into the pump by atmospheric or head pressure (pressure due to the liquid’s surface being above the centerline of the pump). Consider placing a pump at the top of the mercury barometer above: :: Even with a perfect vacuum at the pump inlet, atmospheric pressure limits how high the pump can lift the liquid. With liquids lighter than mercury, this lift height can increase, but there’s still a physical limit to pump operation based on pressure external to the pump. This limit is the key consideration for Net Positive Suction Head.:::

NPSH can be defined as two parts:

AND