Aqueous ethylene glycol solution

Ethylene Glycol Solution: Concentration, Freezing Temperature and Selection

An ethylene glycol solution is a mixture of ethylene glycol and water. It is used in industrial processes and equipment where the working fluid may be exposed to temperatures below 0 °C.
Within the normal working concentration range, increasing the ethylene glycol concentration lowers the crystallization onset temperature. At the same time, density, viscosity, and other thermophysical properties also change.
When selecting a solution, determine:

• the minimum temperature the fluid may actually reach;
• the concentration required for that temperature;
• whether you need a simple aqueous solution or a formulated heat transfer fluid with functional additives.

For solutions manufactured by LLC “AO Khimprom”, concentration is specified as weight percent (wt.%), and distilled water is used for preparation.

What Does Ethylene Glycol Concentration Mean

For example, 40 wt.% means that 100 kg of finished solution contains:
40 kg of ethylene glycol + 60 kg of distilled water.
Weight concentration should not be confused with volume concentration. A solution containing 40 wt.% ethylene glycol is not the same as one containing 40 vol.%.
This is particularly important when using concentration and freezing-temperature charts: always check whether concentration is given by weight or by volume.

What Concentration Is Required

The following values can be used as a general reference for preliminary selection:

Freezing point and density of ethylene glycol aqueous solutions.

These values are provided for reference. For a specific product, the relevant technical documentation should be taken into account.

At What Temperature Does an Ethylene Glycol Solution Freeze

It is common to say that an ethylene glycol solution “does not freeze at −20 °C” or “does not freeze at −30 °C.”
For technical selection, however, it is more accurate to use the term crystallization onset temperature.
For example, for a solution containing 40 wt.% ethylene glycol, the reference crystallization onset temperature is approximately −24 to −25 °C.
This does not mean that the entire volume of liquid instantly turns into a solid mass at this temperature. It means that crystal formation begins. As the temperature decreases further, the physical state and properties of the mixture continue to change.
Therefore, instead of asking “At what temperature does ethylene glycol freeze?”, a more useful technical question is:
“What is the crystallization onset temperature of an ethylene glycol solution at the required concentration?”

Why the Highest Concentration Is Not Always Better

Increasing the ethylene glycol concentration lowers the crystallization onset temperature, but it also changes the properties of the working fluid.
Compared with water, an aqueous ethylene glycol solution has different:
• density;
• viscosity;
• specific heat capacity;
• thermal conductivity.
These properties depend on both concentration and temperature.
Therefore, a higher ethylene glycol concentration does not automatically mean better system performance.

Follow the link and read all the characteristics of the propylene glycol solution

For individual selection and calculation of the necessary liquid in the system heating or cooling please contact our technical specialists.

Click on the link and see all options for heating fluids based on propylene glycol, glycerin and ethylene glycol

Freezing point of aqueous solutions of ethylene glycol depending on concentration.

Aqueous Ethylene Glycol Solution vs. Formulated Heat Transfer Fluid

These are two different types of products.
Aqueous Ethylene Glycol Solution
Ethylene glycol solutions manufactured by LLC “AO Khimprom” consist of:
ethylene glycol + distilled water.
They contain no:
• corrosion inhibitors;
• antifoaming agents;
• stabilizing additives;
• other functional additives.
Such a product can be used as an industrial raw material, as a component in manufacturing, or in equipment that permits the use of an uninhibited aqueous ethylene glycol solution.
FREEZLIGHT® Heat Transfer Fluid
If a ready-to-use working fluid is required for a heating, cooling, or heat transfer system, the system requirements for functional additives must also be considered.
FREEZLIGHT® ethylene glycol-based heat transfer fluids contain a specially selected functional additive package.
The selection principle is therefore straightforward:
if you need ethylene glycol + distilled water at a specified concentration without additives, choose an aqueous ethylene glycol solution;
if you need a formulated heat transfer fluid with a functional additive package, choose the appropriate FREEZLIGHT® product.

Where Are Ethylene Glycol Solutions Used

Aqueous ethylene glycol solutions can be used:

• as industrial raw materials;
• as components in manufacturing formulations;
• for further manufacture of other products;
• in technological processes requiring a specified ethylene glycol concentration;
• in equipment that permits the use of an uninhibited aqueous ethylene glycol solution.

For specific equipment, always check the equipment manufacturer’s requirements for the working fluid.
Ethylene Glycol Toxicity: What Should Be Considered?

Ethylene glycol is toxic if swallowed.

Its use therefore requires particular attention where the working fluid could come into contact with people, animals, food products, or potable water.
If an application has stricter toxicological requirements for the working fluid, a product based on another fluid, such as propylene glycol, should be considered.
The choice of base fluid should therefore be determined by the application requirements and operating conditions, not by crystallization temperature alone.

Can a Plain Ethylene Glycol Solution Be Used in a Heating System

Only if this type of working fluid is permitted for the specific system.
A plain aqueous ethylene glycol solution does not contain corrosion inhibitors. A low crystallization onset temperature alone therefore does not make it a direct replacement for a formulated inhibited heat transfer fluid.
If the system requires a heat transfer fluid with a functional additive package, an appropriate formulated product should be used.

Common Selection Mistakes

Selecting a product only because it says “does not freeze down to −30 °C.”
You need to understand which temperature parameter is being stated and at what concentration.
Using the highest concentration “for extra protection.”
Increasing concentration also changes viscosity, density, and other thermophysical properties.
Calculating the circulation pump as if the system contained water.
An ethylene glycol solution has different physical properties from water.
Assuming that a plain solution is a formulated heat transfer fluid.
A plain solution does not contain a functional additive package.

Ignoring residual water in the system.

Residual water reduces the actual ethylene glycol concentration.
How to Select the Right Product
The selection process can be reduced to four steps:
1. Determine the minimum temperature the working fluid may actually reach.
2. Use the concentration table to determine the required ethylene glycol concentration.
3. Determine whether you need a plain solution without additives or a formulated inhibited heat transfer fluid.
4. For a circulation system, check the requirements for the pump, system materials, and working fluid.
If ethylene glycol does not meet the toxicological requirements of the application, consider an aqueous propylene glycol solution or an appropriate propylene glycol-based formulated heat transfer fluid.

Where to Buy Ethylene Glycol Solution

Novohim offers a ready-made 40 wt.% ethylene glycol solution in distilled water without functional additives.
LLC “AO Khimprom” can also manufacture aqueous ethylene glycol solutions in other concentrations to order.
If you need to prepare solutions of different concentrations yourself, concentrated ethylene glycol is also available.
If you need a ready-to-use working fluid with a functional additive package, choose the appropriate FREEZLIGHT® ethylene glycol-based heat transfer fluid from the Novohim range.

Frequently Asked Questions

At what temperature does a 40% ethylene glycol solution freeze?
For a 40 wt.% solution, it is more technically accurate to refer to the crystallization onset temperature. The approximate reference value is −24 to −25 °C.
What does 40 wt.% mean?
It means that 100 kg of finished solution contains 40 kg of ethylene glycol and 60 kg of distilled water.
Can I order another concentration?
Yes. Aqueous ethylene glycol solutions can be manufactured in different concentrations to order.
Do these solutions contain corrosion inhibitors?
No. Products in this category consist of ethylene glycol and distilled water without functional additives.
Is a more powerful circulation pump required?
The pump should be selected using the actual properties of the ethylene glycol solution rather than water-only parameters. The required adjustment depends on concentration, temperature, flow rate, and the hydraulic resistance of the specific system.
What is the difference between an ethylene glycol solution and FREEZLIGHT®?
A plain solution consists of ethylene glycol and distilled water. FREEZLIGHT® is a formulated heat transfer fluid containing a functional additive package.
Which should I choose: ethylene glycol or propylene glycol?
The choice depends on the operating temperature, equipment, and toxicological requirements of the application. Where stricter toxicological requirements apply to the working fluid, propylene glycol-based products should be considered