Insulating Glycol Lines - What R Value?

[Alphaacid]

I'm trying to figure out which thickness of armaflex I should get for my copper glycol pipes? The glycol unit is out side and I have 9' of 1" outside, 10' of 1.5". Inside we have 79' of 1.5" and 150' of 1".

I can get R value of up to 16, which is I think 2" thick, but that almost triples my cost. Trying to find a happy medium of efficiency and cost.

Currently I cannot get any of my tanks below 36F.

[gvh_Dan]

These numbers come from the 2014 ASHRAE Refrigeration Handbook. The insulation levels are such to prevent condensation on outside jacket surface or limit heat gain to 8 Btu/h·ft2, whichever thickness is greater, at specified conditions. (90°F Ambient Temperature, 80% Relative Humidity, 0.9 Emittance, 0 mph Wind Velocity for indoor piping) (100°F Ambient Temperature, 94% Relative Humidity, 0.1 Emittance, 7.5 mph Wind Velocity for outdoor piping)

I'm using a glycol temp at 20F or relatively close.

Inside pipe
1" pipe = 1.5 inch insulation
1.5" pipe = 1.5 inch insulation

Outside pipe
1" pipe = 1.5 inch insulation
1.5" pipe = 2.0 inch insulation

Understand that these numbers don't have a safety factor built in and are for these specific conditions. If the piping inside goes through a very humid area and if you can't have any condensation, you would want to go thicker.

[gvh_Dan]

With all that said, why do you think you can't get below 36F? Usually the heat gain in piping is relatively small. Are your tanks properly insulated? What is the temperature of the glycol leaving the chiller? What's the temperature when it arrives? If the piping is to small and the pumping is too large, the friction/pumping power can raise the temperature.

[dast]

Hi,
I f you please give me your ambient temperature, fluid temperature and hunidity I can calculate what thickness you need.

Cheers!

Dan Strömberg
Cooling Market Segment Manager
Georg Fischer LLC
Phone: +1 714 368 4196
Fax: +1 714 368 4197
Mobile: +1 951 642 2339
Dan.Stromberg@georgfischer.com

GF Piping Systems
9271 Jeronimo Rd., Irvine, CA. 92618
United States

https://www.gfps.com/us

[Alphaacid]

Ambient temp is 73F, glycol temp is 26F or 27F, 40%-60%humidity.

I dont "think" I can't get the tanks below 36F, I just can't. I can set temp to 34F and they rarely drop below 37F.

Maybe I should drop my chiller temp to 20F, add 1.5" insulation. Then I have to test to make sure my glycol:H2O is accurate. I was thinking about getting $20 test strips to know the current freezing point of my glycol.

[TGTimm]

98' of 1" line looks like a lot of restriction to me. A 90 elbow (IIRC) adds the equivalent of 3' of restriction, so those matter, too.

[Alphaacid]

I didn't install it, so I'm not sure. I just want to get my lines insulated properly.

[gvh_Dan]

By "think" I meant what do you think the reason is. I wasn't doubting your ability to read a temperature gauge.

There are several things that could be going on. Some already suggested by you and Timm.

Its possible the glycol concentration is too high, in which case you aren't getting enough capacity and it requires extra pumping power. Make sure that is as low as it can be.

Its possible the piping is to restrictive and you just can't get enough glycol to the load. It would be nice to assume it was installed correctly, but...

You may want to try turning the glycol temperature up. I know this seems odd but there are two things that could be happening. First as you turn the temp up, the chiller should gain more capacity. Its possible you short on chiller capacity. Likewise, turning the temperature down may cause ice to grow on the heat transfer surfaces resulting in a much slower process. This was the case at a recent client of mine who was running below 20F.

What's the return temperature of the glycol? Its also possible its being pumped through too quickly. This results in a lack of capacity as well because the glycol doesn't hang out long enough before returning to the chiller.