about the pump best operation point 1

[YuriB]

How in a water system: chiller - the (constant speed) centrifugal pump - fancoils (with 3 way valves) the BOP of the pump can in practice be achieved
- at no demand all 3 way valves get closed (system resistance minimal) the system curve moves to the right, far away from the BOP on the pump curve?
- at full demand all valves open (system resistance maximal), system curve goes to the left, far away from the BOP ?

 

[1gibson]

Error - answer does not fit in this little text box.

 

[Artisi]

What is the question?

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.)

 

[BigInch]

Specify the BEP at the flowrate where you will use the most power during the lifetime of your project.

Lifetime power is,
[Σ]Q_n * T_n * Density * H_n
/ E_n
Q_n is the flowrate _n,
T_n is the time operating at that flowrate_n,
H_n is head at flowrate_n
E_n is efficiency at that flowrate_n

Break up your flowrate range into smaller ranges and calculate the lifetime power for each range. Pick a pump with a BEP equal to the flowrate_n that has the highest lifetime power consumption and head should at least equal = H_n, but also be sure that H is chosen to provide the highest head needed too.

It fit in the box.


Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso

 

[YuriB]

My colleages - mechanics have been recently pressurising a system hoping to get rid of the noise from the pump. I think as weather is getting colder now (the chiller runs throughout the year), the demand lessened, most 3 way valves are closed : head is low. The flow control with VFD should be installed ?
(sorry that I do not give system data here as I do not work with it personally)

 

[EdStainless]

Try calculating system points for various flow/VFD combinations. Make sure that that there is actually some advantage to using a VFD.

I have seen systems that were better off with just two speed operation.
Remember how in-efficient motors are working off-frequency.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[YuriB]

They were actually fighting accidental noise from the receiver tank (before the pump) - not from the pump itself.

I believe VFD is good on a chiller pump, notwithstanding the motor may be inefficient energy consumption wise. Exactly with changing demand and thus system curve it keeps the flow constant - what is needed for the refrigeration tract.

 

[BigInch]

If your head varies with the square of flow, it might be so. You need to check that.

Only put off until tomorrow what you are willing to die having left undone. - Pablo Picasso