Pump head calulation

[Jams_imported]

pls, apology me to ask the question which is asked many times.
but here I have some confusion..

That, for the pump head calculation of the closed loop system (Chilled Water System), here we need to consider only the friction losses not any other like velocity and static. and finally the summation of the all friction losses become the pump head with some percentage for safety.

But here what I understand is, We are calculating only the losses occur due to friction in the pressure which is developed by the Pump.

as stated above if we consider only the frictional losses, then what about the pressure needed to obtain desired flow rate or Velocity.

Am I correct?

Thanks, in advance.

 

[Artisi]

The head across the pump is the sum of all the friction losses resulting from the flowrate, the static head on each side of the pump cancel each other.
Not really my area of expertise - so hopefully you get a bit more from the guy's/ gal's on the fine tuning of such a system.



It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[PS]

Losses in a CHW piping system occur due to flow of chilled water and NOT merely due to pressure. To be specific, pump creates a pressure difference between two points in a pipe. This in turn makes water to flow from high pressure point to low pressure point. This flow causes the frictional pressure drop. When the flow rate is high the pressure drop due to friction is high. Since the entire loop is being filled with water, one need NOT account for static head. One will NOT transport water here but rather circulate.

We will also account for losses (due to friction because of flow) across cooling coils, valves, chillers, and other water side accessories.

Hope the information helps you!

 

[willard3]

You should ask a seasoned engineer in your office this question.

 

[lilliput1]

The pressure drop tables or charts for piping indicate pipe sizes and gpm flows thus they include velocity head losses as well as friction losses. The table/chart of pipe pressure drop for open system is higher than that for closed system because more pipe corrosion allowance in included for open piping systems. You must also include equipment (coils, heat exchangers, valves, etc) pressure drops to the piping pressure drop. For open systems you must also include the fluid static head.

 

[ChasBean1]

"But here what I understand is, We are calculating only the losses occur due to friction in the pressure which is developed by the Pump."

No, the sum of the friction losses is by your loads, not your pump. Your loads will create the sum of friction losses through piping, piping bends, and most importantly coils, control and balancing valves.

The pump does not develop the friction losses, but should be designed to overcome them.

 

[MTES93]

Friction loss in pipe as well as dynamic losses at fittings, valves... etc...