Pump Question CERM Ch 18 Q7

[Dano_PE]

In Chapter 18 Question 7 of the CERM sample questions they solve for the total dynamic head without taking into account the atmospheric pressure.

For instance in question 1 it is solved by converting the pressure at inlet and outlet(gage pressures) to absolute pressures (Example ; Poutlet= 14.7psi + 20psi = 34.7psi(roughly))

In question 7 they do not do this. They just use to pressure gage and do not convert it to absolute pressure.

I understand everything else. I am just hung up on when and when not to convert the gage pressure to absolute pressure.

Any input is great!!

 

[Dano_PE]

I am all set.

I attempted to do the problem with the atmospheric pressures to see if I got the same solution and I did not.

The inlet was P=0psi (I forgot that 0psi gage is the same as 14.7psi absolute).

Now it works out correctly.