Glycol Systems

Glycol System Heat Exchangers

What Antifreeze Actually Costs You

Glycol appears wherever a circuit is exposed to freezing ambient: snow melt loops, rooftop equipment, outdoor process cooling, and any system that might sit idle in winter. It also appears where a fluid must not freeze even briefly, because the consequence of a burst coil is out of proportion to the cost of protection.

Glycol is not water with antifreeze in it. It is more viscous, less thermally conductive and has a lower specific heat. All three work against the duty at once: the film coefficient falls, the pressure drop rises, and more mass flow is needed to move the same heat.

Size for the cold condition. Viscosity rises steeply as temperature falls. A loop comfortably turbulent at operating temperature can be laminar at startup on a cold morning, and once flow goes laminar the coefficient collapses and warm-up takes far longer than predicted.

Concentration costs performance permanently. Every percentage point above what the freeze protection genuinely requires reduces heat transfer and raises pumping power for the life of the system. Loops are routinely over-concentrated on the theory that more must be safer.

Propylene or ethylene. Propylene wherever any possibility of food or potable contact exists, since it is far less toxic. Ethylene otherwise, because it is less viscous and performs better thermally at the same concentration.