Pump Head Calculation In high rise 2

[HVACDomain]

hi guys,

Could you please help in calculating head of closed loop system in high rise building.
I am quite confused, as in closed loop piping we dont consider head loss due to elevation(static lift) , i have seen some article on internet in which they have considered some hydro static pressure.
In closed loop system, we consider head loss through piping friction,fittings and equipment like chiller,AHU etc.
but in the article they have considered the static lift also.



Please guide me on this.

I am attaching the file please see pg 81 chapter-7

 

[Hatem2014]

Timothi
Yes, this confusion only occurs in the case of closed loop because regaining pressure during down flow as you said

 

[Hatem2014]

Timothi
But with regard to velocity pressure is not our topic now to avoid more confusion

 

[Hatem2014]

HVACDomain,

Assume we have 150 meters tall building and the pumps installed in zero level
then, after finished installation we will fill the network by water
If we take the pressure gauge reading before running the pumps at zero level we will read about 15 bar . the pressure will be the same at discharge and suction line of pump and equal 15 bar.
This pressure is generated by the elevation without running pumps and without moving water means without pressure drop due to friction and fittings , .....
After running pumps we will obtain more than 15 bar pressure at discharge point of pump may be for example 20 bar

 

[Hatem2014]

PEDARRIN2,
You are right, so it is more economic to install equipments in high level as you can because you will need no strong equipments to bear high pressure

 

[Timothi]

For a closed loop system, only frictional loss due to pipe run, valves & fittings is applicable. You can follow "equivalent length method" to calculate total frictional loss in your closed loop system.

Sharing knowledge is the best way to learn

 

[cchen100]

Hi, everybody,

Question:

I have a closed chilled water system driven by a centrifugal pump.
The outlet of the pump is 1.5" horizontally and the pipe diameter is enlarged to 3" horizontally.
If I put a pressure gauge on 1.5" pipe and the other on the 3" pipe, what do I expect from the readings?

Theory 1:
The flow speed is higher at the 1.5" pipe, so the pressure should be lower at the 1.5" pipe.

Theory 2:
With friction loss ignored, the reading should be the same as the pump head is the same.

 

[LittleInch]

CChem,

1) It is not good practice here to hijack someone else's thread, even if closed for along time. Just start your own. Don't do it again.

2) Is this homework??

3) There will be a difference due to the velocity head, but most times this is negligible and makes no difference or is not seen by a pressure gauge unless very well calibrated together. A differential manometer might show you the difference, but it would be difficult to factor in the friction and the effect of the reducer accurately.

If the same pump fed both pipes and you swapped flow between them you might get somewhere, but this is pretty academic.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EnergyProfessional]

HVAC doamin: two diffeent pressures. All frictionlosses are for pump capacity sizing. Basically how much water the pump can pump. this would be the same if the same piping system is 900 ft high, or 900 ft wide.

the static pressure depends on height and is important for selection of equipment, relief valves etc. so it doesn't "explode" at the highest pressure. You need to imagine the hydro-static pressure + the pump pressure at tha tlocation. Pump pressure at pump suction side is zero, at discharge the max what the pump can do (assume someone overrides the VFD).

Consider gravity of fluid. for water every 2.3 ft you increase by one psi. this will be less for lighter fluids, more for denser fluids.

google concept of "point of no pressure change" and buy this book