During a test on a water pump, no cavitation is detected when the gage pressure in the pipe at the pump inlet is 9.9 psi, and the water temperature is 80°F. The inlet pipe diameter is 4 in., the head across the pump is 115 ft, and the discharge is 13 gal/sec.
(a) Compute the NPSH and the cavitation number if the atmospheric pressure is 14.7 psi.
(b) If the pump is to produce the same head and discharge at a location where the atmospheric pressure is 12 psi, what is the necessary change in elevation of the pump relative to the inlet reservoir to avoid cavitation?