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chiller-001
26-09-2017, 11:17 AM
Hi everybody,
does anybody know exactly where should the chilled water pumps must be installed in a chilled water plant? i mean should they be befor chiller or after it? and why?
thank you everyone

chemi-cool
26-09-2017, 11:43 AM
Sucking from the system and discharging into the heat exchanger. Flow control after the heatexchanger on the discharge line.

mbc
26-09-2017, 04:50 PM
Hi
Also in all pump's our mechanical action give us heating (inlet temperature is lower than out let )
So it is better we suck from system and pump to evaporator
And viscosity of cold water is more than hot water
And in efficiency we have a little difference between them

Expantion tank should be in suction line

Grizzly
26-09-2017, 05:01 PM
Sucking from the system and discharging into the heat exchanger. Flow control after the heatexchanger on the discharge line.
Spot on Chemi!
Grizzly

malik55
26-09-2017, 10:02 PM
Before chillers, this will provide positive pressure to the chillers and also pump strainer will keep dirt off from chillers water side tubes.

chiller-001
03-10-2017, 09:24 AM
thanks everybody for answers.
but if we want to compare these two condition based on the possibility of cavitation isnt it better to put the pumps after chiller where the temp is lower and possibility of cavitation is less?

chemi-cool
03-10-2017, 12:53 PM
Cavitation has nothing to do with place of the pump. It has a lot to do with the pump metal qality and cleanles of tha water from small particles and sand.

Brian_UK
03-10-2017, 02:47 PM
Pump cavitation can occur on either side of the pump due to incorrect pressures causing low suction pressure or high discharge pressure.

Always maintain clean water and water strainers also ensure that the pump selection is correct.

Josip
03-10-2017, 10:28 PM
Hi, chiller-001


thanks everybody for answers.
but if we want to compare these two condition based on the possibility of cavitation isnt it better to put the pumps after chiller where the temp is lower and possibility of cavitation is less?


It is better to install pumps before chiller .... because you have a pressure drop within chiller...

one request: can you, please, upload scheme of your chilled water system ...

Best regards, Josip

nike123
05-10-2017, 08:16 PM
Regarding cavitation, like in boiler heating aplications, pump should be close coupled with expansion vessel and right after it! Expansion vessel is point of no pressure change (PONPC).
Here is reasoning:

The wise a55 in me wants to simply ask; 'Why not?'

Let's see if I can keep this concise...

For various reasons, in the past, circulators were placed on the return side.

Newer materials improved the heat resistance of the pumps, and now they can be placed pretty much anywhere in the system.

The single biggest reason to 'pump away' is to improve the process of removing air from the system.

When system pressure is higher, air has a greater tendency to stay in suspension in the water.

The point in the system that the expansion tank is connected is called the "Point Of No Pressure Change" or PONPC.

The system pressure is HIGHEST at the DISCHARGE side of the circulator pump, and LOWEST at the SUCTION side.

When a system is configured such that the pump is pumping TOWARD the PONPC, then when the pump is running, it SUBTRACTS pressure from the rest of the system, and vice versa, when it is pumping AWAY from the PONPC, it ADDS pressure to the rest of the system.

The AIR ELIMINATION DEVICE should ALSO be placed at the PONPC, so that when pumping away, the air elimination device is at the lowest pressure point in the system. And the rest of the system is at a higher pressure.

The net result is that the air in the water more easily travels through the system, remaining dissolved in the water (or smaller bubbles because they are 'squeezed' more by the higher pressure), and are more easily 'caught' by the air elimination device at the lowest pressure point in the system.

Also, HOT water has less capacity to hold air. If the PONPC also happens to be on the HOT SUPPLY side of the boiler, air elimination becomes another bit easier to achieve.

Not concise really, but hope it helps!


Also good to read this: http://www.reflex.de/fileadmin/user_upload/pdf/FI0120en_9571116_Planung_Berechnung_Ausruestung.pdf

http://www.doityourself.com/forum/boilers-home-heating-steam-hot-water-systems/406300-why-pump-away.html