Certain types of heating systems, such as closed-looped thermal fluid heating systems, can use glycol to maintain heat transfer fluid to the desired temperature. While water is an ideal heat transfer medium for a certain range of temperatures, pure water has drawbacks. It can freeze below 32° F and it can corrode the internals of a heating system. Also referred to as antifreeze, glycol lowers the freezing temperature of the mixtures it is added to and it ensures that harsh weather conditions do not cause heating systems to freeze. In addition, glycol raises the boiling point of water to some degree, allowing for higher operating temperatures with less operating pressure than pure water. Glycol is also frequently purchased with corrosion inhibitors that reduce corrosion inside of the system over time.
Why Are Glycol Heaters Important?
Without adding glycol to a heating system, expensive and potentially dangerous damage to process equipment can occur. If the heating system is shut off for some time during the winter, the system and its pipes can freeze and burst, causing water damage. In addition to preventing system freezing, glycol mixtures are also a very efficient heat transfer medium compared to oils or water alone. Water and glycol mixtures have a better heat capacity than oils and perform well in many types of heaters. There are temperature limitations relative to thermal oils, but within the right range, a water-glycol solution is an excellent choice.
Additionally, glycol heaters are valuable due to the safe heat transfer that they provide. For example, it can be dangerous to have heating elements near the process or materials, but using a glycol heating system keeps the heat source safely away from the process. Thermal oils are also a fire hazard if there is a system leak, while glycol solutions are not flammable.
Using Glycol in Industrial Heating System Applications
Ethylene and propylene glycol are commonly used in industrial facilities for process cooling. However, they are also used in process heating systems. They are very effective in heating applications due to several properties, such as:
- High specific heat capacity
- High thermal conductivity
- Low viscosity
- Water miscibility
Water and glycol solutions present many benefits for industrial processes, on the other hand, these are not the only heat transfer mediums available. Synthetic and organic thermal oils are also sometimes selected as they work well in temperatures up to 750° F and produce very little vapor pressure. Water without additives can also be used, although within more limited conditions due to its low-temperature intolerance and boiling point. It is also possible for water to produce a dangerous amount of vapor pressure at certain temperatures.
A water and glycol mixture can be a preferable choice in many applications since it has a higher boiling point than water alone, which can be increased further by including a higher concentration of glycol. Different types of glycol can be used for varying operating temperatures. For example, while ethylene and propylene glycol are suitable for systems with temperatures between 250–300° F, Tri-ethylene glycol works effectively up to 350° F.
Glycol Heaters from Sigma Thermal
Sigma Thermal’s glycol heaters, such as HC-2 heaters, are designed to meet all area classifications and can perform optimally in even the harshest of environments, including deserts, arctic, and offshore regions. The HC-2 thermal fluid heater is available in capacities from 1 to 100MM Btu/hr, with custom sizes also available. The heater shell is externally insulated using mineral wool insulation which is covered in aluminum cladding.
Some other design features of glycol heaters from Sigma Thermal include advanced control system options and a double-helical coil design, which offers three passes of flue gas along a conservatively designed coil surface area. Depending on process inlet temperatures, base efficiencies can exceed 88%, and by including an optional economizer, can exceed 93% (LHV basis).
These systems allow flue gases to be cooled significantly, which eliminates the need for most internal shell insulation. Sigma Thermal carries low emissions burners that meet all emissions requirements in standard or engineered burner configurations that can be used with either traditional or alternative fuel sources.