Can I use glycol as a heat transfer fluid?

ATC recommends Hexid or CoolFlow inhibited glycol-based coolants for standard products.

These approved fluids have been selected to provide:

• Corrosion protection
• Biological growth inhibition
• Reliable long-term thermal performance
• Protection of pumps, seals, and heat exchangers

Using an approved inhibited coolant helps to protect the complete cooling circuit as well as supporting reliable thermal performance.

One of the most important functions of a glycol-based heat transfer fluid is to provide freeze protection.

This is particularly important when a chiller operates at lower fluid temperatures, where water alone could freeze and potentially damage components within the cooling circuit.

An inhibited glycol-based coolant also provides additional protection for components within the system, including protection against corrosion and biological growth.

Ethylene glycol (CoolFlow) and propylene glycol (Hexid) are both commonly used as the basis of heat transfer fluids, but they have different properties and are suited to different applications.

Ethylene glycol generally offers good heat transfer performance and lower viscosity, which can be beneficial for pumping and thermal performance, particularly at lower temperatures. However, ethylene glycol is toxic if ingested and may therefore be unsuitable for applications where accidental contact with food, beverages, or other sensitive processes is a concern.

Propylene glycol has lower toxicity and is therefore often considered where the consequences of accidental exposure are an important consideration. However, propylene glycol solutions are generally more viscous than equivalent ethylene glycol solutions, particularly at lower temperatures. This can increase resistance within the cooling circuit and influence pump and heat transfer performance.

The choice is therefore not simply a question of which glycol is “better”. The fluid formulation, concentration, operating temperature, and cooling system design all need to be considered.

The appropriate concentration depends on the approved coolant and the required operating temperature range.

The concentration needs to provide suitable protection for the conditions in which the chiller will operate.

Customers should therefore follow the fluid and concentration requirements specified for their ATC chiller and application rather than selecting a concentration independently.

If you are unsure which concentration is required, contact ATC with your chiller model and required operating temperature.

Changing the concentration of a heat transfer fluid changes its physical and thermal properties.

This can affect how effectively heat is transferred and how the fluid behaves as it moves through the chiller and application.

Fluid selection should therefore be considered alongside the required operating temperature, coolant flow, and wider application requirements when the chiller is specified.

Using more glycol than required should not be assumed to provide better performance.

If your application requires a fluid outside of ATC’s approved standard process fluids, tell us before selecting or commissioning the chiller.

Alternative fluids may require review by ATC to assess their suitability and compatibility with the cooling circuit.

Depending on the fluid and application, a non-standard cooling circuit specification may be required.

See “How do I choose a heat transfer fluid?“ for an overview of ATC’s approved process fluids and guidance for applications requiring water, DI water, oil, or another specialist coolant.

For standard ATC chillers, the key principle is to use the approved Hexid or CoolFlow inhibited glycol-based coolant specified for your equipment and operating conditions.

Contact ATC if you are unsure which process fluid or concentration is appropriate for your chiller.