Glycol concentration and heat transfer

[blacklabs]

In a closed loop cooling system designed to run at 50% Glycol/50% Water, the concentration has dropped to 30% glycol. How will this affect heat transfer capabilities. The temperature range for this fluid is approx. 60 - 120 degF.

 

[IRstuff]

It should get better. Pure water has the best performance in this type of design.

If you are never going below 60°F or above 120°F, why are you using glycol at all?

TTFN

FAQ731-376

 

[blacklabs]

Freeze protection for sections that may be isolated during maintenance. Thanks

 

[IRstuff]

Oh, OK, so the question then is how cold do you need to protect against. 50/50 gets you to around -30°F. 30/70 only gets you to about 0°F.

TTFN

FAQ731-376

 

[JohnnyHS]

As the concentration of glycol in the solution increases the thermal performance of the heat transfer fluid decreases. This is the good point IRstuff was saying.

Therefore it is best to use the lowest possible concentration of glycol in your mix to meet your freeze protection needs.

So good news! Your cooling has become more efficient! (but less freeze protection which doesnt seem to be a problem? so win win?)



Johnny H-S BSc(Hons) MInstMC

Engineers like to solve problems. If there are no problems handily available, they will create their own problems.

 

[blacklabs]

Thanks to all for the help!

 

[romke]

there may be another reason for the concentration of glycol mentioned.

most glycols are sold together with an anti-corrosion package.

if you reduce the glycol concentration, also the concentration of the anti-corrosion additive is reduced. since the anti-corrosion additive is used up during service, this may lead to corrosion problems in the long run.

the heat transfer properties change when the concentration of the glycol changes, but in most cooling systems the capacity is deliberately overrated so this causes no problems as long as you keep the concentration at 50% or lower.