Glycol is a water-miscible antifreeze liquid frequently used in heat transfer and cooling applications. It provides better heat transfer parameters than water, and when mixed with water can provide an array of characteristics. These glycol antifreezes are mainly of two types - Ethylene glycol antifreeze and Propylene glycol antifreeze.
What is an Antifreeze?
Antifreeze coolant primarily function as drawing away heat allowing the engine to operate efficiently, lessening malfunctions and damages to its parts. A cooling system uses pumps, hoses, thermostats and a radiator, but the primary component is the coolant chemical itself, which keeps the engine from boiling in the hot days, and freezing in the cold days.
Types of Glycol Antifreeze
Propylene glycol is most often used near food applications and Ethylene glycol for industrial applications, owing to its increased toxicity. In addition to excellent heat transfer properties, ethylene glycol prevents algal growth inside heat transfer equipment.
Water would be the ideal heat transfer fluid for cooling applications, if it did not freeze when freeze conditions exist viz., <1.67°C/ 35 F). The main purpose of an antifreeze is to help in the prevention of a definite enclosure from bursting due to expansion when water freezes. Glycol can be added to water to provide freeze and burst protection. Glycol has lower heat transfer efficiency than water and is denser, resulting in higher volumetric flow rates or heat exchange areas required to maintain the same temperature levels. Water volume expands by 9% when frozen. Glycols depress water’s freezing point providing protection to temperatures as low as -56.67°C / -70 F to -73.34°C/ -100 F. Freeze protection prevents ice crystal formation at the lowest temperature expected in the coolant circuitry, necessary for year-round pumping. Burst protection requires less glycol and allows some freezing to turn the coolant into a slush, not causing the pipes to burst. This method is used in closed circuits that are not operated in cold weather.
Chemtex manufactures glycol antifreeze for protection against algae and biofilms along with heat transfer properties. The use of an inhibited glycol and water mixture is recommended for most chiller systems. The main job of glycol is to prevent freezing of the process fluid and ensure a consistent flow rate at the operating temperature. Inhibited glycols also prevent formation of scale and corrosion, and protecting metals such as brass, copper, steel, cast iron and aluminum.