Chilled Water Pipe Velocity

[Buildtech2]

As per attached ASHRAE reference, the recommended lowest chilled water pipe velocity to be maintained in chilled water pipes is 0.6 m/s. In my current fit-out project, I have to use existing chilled water pipes for new fit-out flow rates where the pipe velocities are dropping below 0.6 m/s. I am assuming there won't be any major impact with such lower velocity. Appreciate, if anybody can advice on this issue.

 

[EnergyProfessional]

The only downside is that it may be a tiny bit harder to get air out. but with proper location of de-aerators it should work. with variable flowrates you go under the design flowrate much of the time anyway.

Your existing modulating control valves may have too little authority unless you replace them with smaller ones (I'm assuming your project for some reason reduces flowrate from original design). Something to verify. Also the pumps now may be too large.

 

[dbill74]

It will depend on how much lower you go below 0.6 m/s. If you don't go below 0.5 m/s I can't imagine any issues.

Aside from the air removal mentioned by EnergyProfessional, I can imagine fouling as a potential problem as the water is more likely to deposit any dissolved solid.

How old are the existing pipes? Have they sat idle before your fit out? If so, for how long? What are the materials of the existing pipie? You could make the case for replacing.

Have you or anyone run a camera through the pipe to inspect the interior?

 

[EnergyProfessional]

i don't see fowling at low flow...... if that was true, the system would foul when it is shut off or when flow rate is low like in variable flow systems.

 

[LittleInch]

Well the section you copied in specifically relates to air entrainment and the fact that at 0.5 to 0.6 m/sec the air will generally be swept along to a suitable venting point.

Lower than that it might not or it might be swept along as a bubble or slugging.

So how you deal with entrained air in your existing pipes might need some enhancement to vent air at high points where previously you wouldn't have bothered.

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

 

[Buildtech2]

Thanks everybody for your valuable responses. Much appreciated.