derating cooling coils for chilled water with glycol
derating cooling coils for chilled water with glycol
(OP)
I am inquiring about a derating factor to be applied to the performance (sensible & latent)of a chilled water coil with 30% propylene glycol. The chiller mfg. suggests a 5% derating for the chiller performance. Is this derating the same for the coil/air handler. If not, why not?





RE: derating cooling coils for chilled water with glycol
http://www.dow.com/heattrans/prod/glycol/
RE: derating cooling coils for chilled water with glycol
You can find the new K value from the data in ASHRAE, but it is dependent on the % of the solution and the water temperature. If I assume that the water temp. is about 40 degrees F and the delta T is 12 degrees F, your new "K" value for your situation is 471. 471/500 = .942 or about 6% less.
In short, the derating of your coil will depend on the percent of glycol and the temperature of the water, but you are looking at about a 5 - 6 percent derating. So what the manufacturer told you for the chiller should also applies to the coil. FYI the colder the water temp the more the derating factor there is for the glycol.
RE: derating cooling coils for chilled water with glycol
I agree with you but when I was sizing cooling coils with a mfgs. rep., he said the output he was getting from his program derated the output by 30%. It did not make sense to me that the derating factors would be different from chiller to air handler/cooling coil.Ever heard of that?
RE: derating cooling coils for chilled water with glycol
Now I can't tell you that these problems haven't been fixed or that the program you were using had that same issue, but that is my experience with it.
If you still aren't sure call a few sales rep from Carrier, Trane, York and just ask them as a general question how there cooling coils would be derated by adding 30% prop. glycol.
RE: derating cooling coils for chilled water with glycol
It shouldn't be, but maybe I am missing something.
RE: derating cooling coils for chilled water with glycol