Choos­ing a heat trans­fer flu­id (glycol) for cool­ing and heat­ing sys­tems

The heat trans­fer flu­id is a part of the sys­tem that is rarely seen but affects everything. It car­ries heat or cold from one place to anoth­er, pro­tects the net­work against freez­ing and slows down cor­ro­sion. The qual­ity and age of the flu­id affect both heat trans­fer per­form­ance and sys­tem safety.

A flu­id that is wrongly selec­ted or used at the wrong con­cen­tra­tion can reduce per­form­ance, increase the pump­ing energy required or, at worst, let the net­work freeze. This guide cov­ers what to con­sider when choos­ing a heat trans­fer flu­id.

Ethyl­ene or pro­pyl­ene glycol?

The most com­mon heat trans­fer flu­ids are ethyl­ene glycol and pro­pyl­ene glycol. Cor­ro­sion inhib­it­ors are added to both. The choice depends on wheth­er the applic­a­tion pri­or­it­ises tech­nic­al per­form­ance and price or safety.

Prop­erty	Ethyl­ene glycol	Pro­pyl­ene glycol
Typ­ic­al applic­a­tions	Indus­tri­al and build­ing HVAC sys­tems, ice rinks	Food industry, cool­ing pro­cesses, ice rinks
Vis­cos­ity	Lower, the flu­id flows more eas­ily	High­er, espe­cially in the cold
Heat trans­fer	Good	Slightly lower due to the high­er vis­cos­ity
Freez­ing point as a 50% solu­tion	approx. −36 °C	approx. −33 °C
Safety	Harm­ful if swal­lowed	Less haz­ard­ous, but not com­pletely non-tox­ic
Price	Lower	Usu­ally high­er

Ethyl­ene glycol suits applic­a­tions where tech­nic­al per­form­ance and cost-effect­ive­ness mat­ter most. Its lower vis­cos­ity and good heat trans­fer make it a com­mon choice for heat­ing and cool­ing sys­tems in industry and build­ings. How­ever, ethyl­ene glycol is harm­ful if swal­lowed, so it is not used where a leak could end up in food (Finnish Insti­tute of Occu­pa­tion­al Health, OVA guide).

Pro­pyl­ene glycol is chosen when safety and the spe­cif­ic require­ments of the applic­a­tion carry weight, as in the food industry. It is thick­er and usu­ally more expens­ive than ethyl­ene glycol. Achiev­ing the same freeze pro­tec­tion requires a slightly high­er con­cen­tra­tion.

Cool­ing solu­tions are a third option. For example, ECO-FROST is a cool­ing solu­tion for indir­ect sys­tems such as street heat­ing, the food industry and ice rinks. It is non-flam­mable and envir­on­ment­ally friendly, with a high spe­cif­ic heat capa­city and low vis­cos­ity. For large sites such as out­door ice fields, ice rinks and industry, Ves­iTekno also sup­plies salt solu­tions.

How to choose the right heat trans­fer flu­id

Go through these ques­tions before you order.

1. Which sys­tem is the flu­id for?

Heat trans­fer flu­ids are used, for example, in heat­ing and cool­ing sys­tems in industry and build­ings, in heat­ing for arti­fi­cial turf pitches, in ice rinks, in refri­ger­a­tion plants and in food industry pro­cesses. The applic­a­tion often determ­ines on its own wheth­er ethyl­ene glycol is suit­able or wheth­er pro­pyl­ene glycol or ECO-FROST cool­ing solu­tion is needed.

2. How cold can the sys­tem get?

The flu­id con­cen­tra­tion is determ­ined by the low­est tem­per­at­ure the sys­tem may be exposed to. The high­er the glycol con­cen­tra­tion, the lower the freez­ing point. How­ever, the con­cen­tra­tion should not be raised more than neces­sary, because glycol trans­fers heat less effect­ively than water.

3. Does the site have safety require­ments?

If a leak could end up in food or the envir­on­ment, safety car­ries weight in the choice. The options are then pro­pyl­ene glycol or ECO-FROST cool­ing solu­tion.

4. What flu­id is in the sys­tem now?

When flu­id is topped up or replaced, it is import­ant to know what is already cir­cu­lat­ing in the net­work. If neces­sary, the com­pos­i­tion and con­di­tion of the cur­rent flu­id are determ­ined by labor­at­ory test­ing.

5. How much flu­id is needed?

The need ranges from a small top-up to filling an entire net­work. Ves­iTekno sup­plies gly­cols in 20-litre jerry­cans, 200-litre drums and 1,000-litre IBC con­tain­ers, as well as by tanker. Orders placed in good time can often be delivered the next day.

After the choice: mon­it­or­ing and replace­ment

A heat trans­fer flu­id does not last forever. Over time its cor­ro­sion pro­tec­tion weak­ens, impur­it­ies build up and its heat trans­fer capa­city can decline. That is why the con­di­tion of the flu­id should be mon­itored reg­u­larly. The gen­er­al recom­mend­a­tion is to inspect the sys­tem once a year.

Check the flu­id and con­sider repla­cing it if:

• the pH has dropped and the con­cen­tra­tion of cor­ro­sion inhib­it­ors has fallen
• the flu­id is cloudy, has changed col­our or con­tains sed­i­ment
• heat­ing or cool­ing per­form­ance has declined for no oth­er obvi­ous reas­on
• there is rust, mag­netite, sludge or clog­ging fil­ters in the net­work
• the flu­id is
• more than 8 years old.

con­di­tion inspec­tion checks the con­cen­tra­tion, pH, freez­ing point and gen­er­al con­di­tion of the flu­id. Based on labor­at­ory ana­lys­is, we assess wheth­er the cur­rent flu­id is still adequate or wheth­er it is time to replace it. If the flu­id is replaced, the net­work is cleaned and flushed as neces­sary before the new flu­id is filled and the sys­tem ven­ted.

Ves­iTekno helps you choose

We do not sell a one-size-fits-all flu­id. We recom­mend a product based on the applic­a­tion. Our range includes:

• ethyl­ene gly­cols and pro­pyl­ene gly­cols with cor­ro­sion inhib­it­ors
• ECO-FROST cool­ing solu­tion for indir­ect sys­tems
• salt solu­tions for large out­door field and indus­tri­al sites.

In addi­tion to flu­ids, we look after the con­di­tion of the sys­tem: flu­id ana­lyses, net­work clean­ing and flush­ing, flu­id replace­ment, filling and vent­ing, and reg­u­lar con­di­tion inspec­tions.

Request a quote for heat trans­fer flu­id

Tell us about the applic­a­tion, the size of the sys­tem and the cur­rent flu­id, and we will recom­mend a suit­able product and con­cen­tra­tion.