Pump Head Req'd

[Dano_PE]

If a pump has a submerged outlet (8' deep in a tank) does it require more head to discharge the water?

The pump is at elevation 12 and the outlet pipe enters the tank at elevation 8 but extends to the bottom of the tank at elevation 0 (8 feet of outlet pipe is submerged in water).

The book does not add this into the solution but it states "this solution assumes no exit/ entrance losses".

I am referring to question 3 in chapter 18 of the CERM book.

Does the pump need more head to push to the water out of the end of the discharge hose which is submerged?

 

[Jacob_PE]

If a pump has a submerged outlet (8' deep in a tank) does it require more head to discharge the water?

The pump is at elevation 12 and the outlet pipe enters the tank at elevation 8 but extends to the bottom of the tank at elevation 0 (8 feet of outlet pipe is submerged in water).

The book does not add this into the solution but it states "this solution assumes no exit/ entrance losses".

I am referring to question 3 in chapter 18 of the CERM book.

Does the pump need more head to push to the water out of the end of the discharge hose which is submerged?

I'm not able to look at the problem now, but the hz depends on two on pieces of information, the water surface elevation from the suction source and the water surface elevation at the discharge point. NPSHA is affected by the position of the pump relative the suction water source elevation, but the total dynamic head required of a pump is the head based on delta z, hp, hv, hf, and hm, (elev, pressure, velocity, friction & minor head loss)

 

[Dano_PE]

JACOB,

if my suction is at elevation say 0

My pump is at elevation 12

discharge at elevation 0 (discharge submerged in a tank 8' deep)

would the Hreq'd change if the discharge was right at the surface of the tank as opposed to submerged in 8' of water?

The problem does not add any but it says "disregarding entrance and exit losses". Would my above description be an exit loss?

As you can see my weak points are pumps and structural design. I guess it could be worse.

Thank you.

 

[Jacob_PE]

JACOB,

if my suction is at elevation say 0

My pump is at elevation 12

discharge at elevation 0 (discharge submerged in a tank 8' deep)

would the Hreq'd change if the discharge was right at the surface of the tank as opposed to submerged in 8' of water?

The problem does not add any but it says "disregarding entrance and exit losses". Would my above description be an exit loss?

As you can see my weak points are pumps and structural design. I guess it could be worse.

Thank you.

If it's just the one 8' deep tank, with 8' of water in it, the answer is no. The water level on the suction and discharge is the same in both cases, whether the discharge pipe is on the floor of the tank or at the water surface level has no effect. Disregarding entrance and exit losses is disregarding minor losses, not elevation head losses. This is a great PE exam question because they want to make sure you know that it's the difference in water surface elevations that matters for the elevation head.

 

[Dano_PE]

Great!! That is what I needed to know.

I agree this is a good concept to know very well.