WHAT IS A HEAT TRANSFER FLUID?
Heat transfer fluids allow either indirect heating or cooling of process reactors, piping, molds, etc. Heat transfer fluids can also be called thermal oil, thermal fluids, hot oil or heat transfer oil. Of the water-based heat transfer fluid category, ethylene glycol (EG) and propylene glycol (PG) fluids are the most common. The key factors for any well-designed heat transfer fluid system are heat transfer efficiency, high purity, and thermal stability.
WHAT IS THE ROLE OF GLYCOL IN INHIBITED GLYCOL HEAT TRANSFER FLUID APPLICATIONS?
The main purpose of glycol is to prevent freezing or overheating of the process fluid and ensure consistent flow at the desired operating temperature. Inhibited glycols will protect metals such as brass, copper, steel, cast iron and aluminum from scale and corrosion. Water systems treated with an inhibited glycol will also be protected from algae and bacteria that can grow and degrade the fluid system performance.
Inhibitors also function to extend the life of the fluid itself. Glycol based coolants will degrade over time into acids. The presence of the inhibitors helps to slow that degradation in a metallic system. These inhibitors also help extend the life in stainless steel or non-metallic systems.
CAN YOU MIX GLYCOLS OR GLYCOL BRANDS?
Do not mix different types or brands of inhibited glycol. This can have negative effects on the system if the inhibitors precipitate out of the solution. Mixing glycols will also gel and clog filters thereby preventing proper flow rates. If switching glycol types, it is necessary to clean the fluid from the system by running a full flush of it. Once that is done, then the system can be filled with the new glycol brand or fluid.
WHY SHOULDN’T YOU USE AUTOMOTIVE GRADE ANTIFREEZE?
Automotive grade antifreezes are designed for automotive use. The majority of automotive antifreezes are made from ethylene glycol as are some heat transfer fluids. However, automotive antifreeze is not designed for industrial applications and may cause problems with heat transfer or fluid flow. For instance, many automotive glycols contain silicate-based inhibitors that can coat heat exchangers, attack pump seals, or form a flow-restricting gel.
IS ETHYLENE GLYCOL SUFFICIENT FOR MOST STANDARD INDUSTRIAL APPLICATIONS?
Ethylene glycol is the conventional heat transfer fluid for most industrial applications. This type of glycol can be used in any application where a low toxicity content is not required. Ethylene glycol has moderately acute oral toxicity and should not be used in processes where the fluid could come in contact with potable water, food, or beverage products.