When should I use glycol in my closed loop system instead of water?

Glycol has antifreeze properties that protect coils in a closed circuit cooler from potential freezing during winter operation in northern climates.  Glycol solutions are rarely used for closed loop systems in warmer climates, such as Florida or Arizona, unless they are being used as corrosion inhibitors.

In general, about half of closed circuit cooler applications use water and about half use glycol.  Which is better for a closed loop system and why?

Water has superior heat transfer properties compared to propylene or ethylene glycol and is more frequently used in the southern half of the United States.  Water is also cheaper than glycol and, in most cases, will result in a smaller unit selection while requiring less pumping HP.

In most cases, the reason to convert a closed loop system from water to glycol is to prevent freezing and the associated coil damage that results when a closed circuit cooler is exposed to lower ambient temperatures.

Closed Loop System Illustration

If water is being utilized in a closed loop system in a northern climate, it is imperative that a minimum flow be maintained at all times. The temperature inside the coil must never drop below 45 degrees F.  Discharge hoods with dampers and padded insulation on the outside of the coil casing section can also help to prevent freezing of the coil if water is being used in a cooler during winter operation. The most foolproof method of protecting a coil from freezing/bursting in northern climates is to use either an ethylene or propylene glycol inhibitor which have antifreeze properties.

Reasons for not converting a closed loop from water to glycol include the capital cost of glycol (especially for larger systems), the reduced heat transfer rate of glycol (i.e., a larger unit would be required to achieve the same heat transfer capacity), and the increased pump HP required for glycol.

All of the above must be weighed when considering whether water or glycol is right for your closed loop system. For more assistance, please contact your local EVAPCO sales representative.