12 questions on head related to 11 years of professional knowledge
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12. When a centrifugal pump is operating normally in a certain piping system, under what condition is the pump head independent of the density of the liquid being transported? A. Z2-Z1=0 B. Σhf=0 C. u22/2 – u12/2=0 D. p2-p1=0. Why is the answer D? Doesn’t a pump increase pressure? How can it be assumed that the pressure difference between the inlet and outlet of the pump is zero? I don’t understand; please advise, fellow users.
Bernoulli’s equation shows clearly that H = Z + U²/2g + P_pressure/pg, where P_pressure = P2 – P1
The problem is that the pump increases pressure; how can the outlet pressure be equal to the inlet pressure? The calculations can be understood, but I think P2–P1=0 doesn’t make any practical sense. Please give your advice
It’s not the pump’s inlet and outlet, but rather its suction inlet and discharge outlet, including the suction pipeline and the discharge pipeline
I still don’t quite understand; are the two open liquid surfaces considered as two cross-sections, with zero pressure that is independent of density? ?
The gauge pressures of both open containers are 0; therefore the pressure difference is also 0. Even in the case of two sealed tanks, as long as the pressures inside them are equal, and using the liquid levels in these tanks as cross-sections, Bernoulli’s equation still applies, and He remains independent of density.