How do I choose a heat transfer fluid?
Choosing the correct heat transfer fluid, or process coolant, is an important part of specifying a recirculating chiller.
The fluid carries heat between your process and the chiller, so the correct selection is important for cooling performance, corrosion protection, and the long-term reliability of components within the coolant circuit.
For standard ATC chillers, ATC recommends Hexid or CoolFlow inhibited glycol-based coolants.
If your application requires a different process fluid, dicuss this with ATC before selecting, filling, or commissioning the chiller.
Which heat transfer fluids does ATC recommend?
For standard ATC chillers, the approved process fluids are:
These inhibited glycol-based coolant have been selected to provide corrosion protection, inhibit biological growth, support reliable long-term thermal performance, and protect components including pumps, seals, and heat exchangers.
The appropriate fluid and concentration should be selected for the operating conditions of your application.
Can I use tap water in my ATC chiller?
No. Untreated tap water is not approved for use within standard ATC chillers.
Tap water varies significantly depending on location and supply. Mineral content, dissolved salts, biological contamination, and water-treatment chemicals can contribute to corrosion, scale formation, and reduced heat-transfer performance.
Over time, this can increase maintenance requirements, reduce equipment reliability, and shorten the service life of the chiller.
ATC therefore recommends using an approved inhibited coolant rather than tap water.
Can I use deionised (DI) water?
DI water is not a standard process fluid for ATC chillers.
Applications requiring DI water are classified as non-standard and must be discussed with ATC Engineering before the equipment is ordered or commissioned.
Because of its low conductivity and particular material requirements, a cooling circuit intended for DI water needs to use compatible components throughout the fluid path.
If your process requires DI water, tell ATC during the chiller specification process so that the application can be reviewed and an appropriate solution considered.
Why does ATC recommend inhibited glycol-based coolants?
The process fluid does more than simply carry heat between the process and chiller.
ATC’s approved inhibited glycol-based coolants are selected to provide:
- Corrosion protection
- Biological growth inhibition
- Reliable long-term thermal performance
- Protection for pumps, seals, and heat exchangers
Using the correct coolant therefore helps to protect the cooling circuit as well as supporting effective temperature control.
Does fluid choice affect chiller performance?
Different fluids and concentrations have different thermal and physical properties.
Properties such as viscosity, specific heat capacity, and thermal conductivity influence how the fluid absorbs and transports heat. Viscosity can also affect resistance to flow through the chiller, pipework, and process.
The required fluid and concentration should therefore be considered alongside the operating temperature, coolant flow, and wider system requirements when specifying a chiller.
What concentration of coolant should I use?
The appropriate fluid concentration depends on the coolant being used and the required operating temperature range.
For lower-temperature applications, sufficient glycol concentration is particularly important to provide the necessary freeze protection.
Do not assume that increasing glycol concentration is always beneficial. Changing concentration also changes the thermal and hydraulic properties of the fluid and can affect system performance.
Follow the recommendations for the approved coolant and contact ATC if you are unsure which concentration is appropriate for your operating conditions.
Can I use a different or specialist process fluid?
Alternative process fluids are not automatically approved for use in a standard ATC chiller.
If your application requires a fluid other than an ATC-approved inhibited coolant, contact ATC before specifying or commissioning the equipment.
The requirement may need to be treated as a non-standard application so that Engineering can consider the fluid’s compatibility with the materials and components throughout the cooling circuit.
Depending on the application, a non-standard cooling circuit specification may be required.
Can I change the fluid in an existing chiller?
Do not change to a different process fluid without first checking that it is approved for your particular chiller.
If you are considering changing the fluid in an existing unit, particularly to DI water or another specialist fluid, contact ATC with the chiller model and serial number, together with details of the existing and proposed fluids.
ATC can then advise whether the proposed fluid is suitable or whether further Engineering review is required.
How can ATC help me choose?
For standard ATC chillers, the starting point is straightforward: ATC recommends Hexid or CoolFlow inhibited glycol-based coolant.
The appropriate product and concentration can then be considered according to your operating conditions.
If your process requires something different, speak to us before selecting or filling the chiller. This allows fluid compatibility to be considered as part of the overall cooling system specification rather than after the equipment has been specified.
Contact ATC if you need help selecting the correct process fluid for your chiller.
