Glycol chiller – definition, applications, how to choose – Complete guide

What is a glycol chiller?

A glycol chiller is a device that removes heat from a liquid using glycol. The fluid can circulate through a heat exchanger (or cooling jacket) to cool equipment, process stream or simply as a utility liquid.

The heart of a glycol system is the glycol chiller. As the name implies, it uses glycol as a refrigerant.

A glycol chiller consists of a compressor, evaporator, condenser, throttling element and electrical control system.

Why should you use glycol for cooling?

You should use glycol for cooling primarily because it has antifreeze properties. Therefore, it is better suited for applications that require lower temperatures.

The most common refrigerant used in chillers is water or a mixture of water and another substance with suitable heat conduction properties such as a glycol compound.

Glycol-based coolants consist of ethylene glycol or propylene glycol. As we have already mentioned, their main advantage is their anti-freezing properties.

Pure water freezes at 0 degrees Celsius, while a mixture with 30% ethylene glycol freezes at -14 degrees Celsius.

The low freezing point of glycol mixtures makes them ideal for cooling components that are below the freezing point of water.

Although glycol has a lower heat capacity (each kilogram of glycol heats up more easily than a kilogram of water), the greater temperature difference allows it to remove heat more quickly. Therefore, glycol mixtures are better suited to applications where the chiller needs to remove large amounts of heat quickly.

Furthermore, glycol slows the growth of algae in heat exchange equipment.

How does the glycol cooling system in a chiller work?

The glycol cooling system in a chiller functions as follows:

1. The refrigerant absorbs heat energy from the process (usually the refrigerant turns into a gas). 
2. The refrigerant in its gaseous state heads to the condenser, which removes heat from the refrigerant via condensation or the cooling tower. 
3. The heat exchange condenses the refrigerant back into a cooler gas-liquid mixture, which goes to the process heating source to start the cycle again.

What are the applications of the glycol chiller?

The most popular applications of the glycol chiller are brewing, wine production, maintenance of ice rinks, processing of dairy products.

Glycol chiller in brewing industry

In breweries, a glycol chiller makes it possible to significantly reduce product temperature in a short period (depending on production needs).

There are several processes in which it is crucial to reduce or maintain cold thermal conditions, such as:

• rapidly cooling beer after fermentation,
• maintaining a constant temperature during fermentation (which generates heat), 
• cooling the fermentation broth after the initial boiling process.

Glycol chiller in wine production

Glycol chillers are used in the wine fermentation process to control thermal conditions.

The temperature of the glycol solution varies depending on the type of wine produced and the preferences of each winemaker, but most wine chillers operate between 2 and 10 degrees Celsius (7 to 15 degrees Celsius for wine containers).

Glycol chiller in ice rink maintenance

The glycol chiller cools the liquid glycol solution to a temperature well below the freezing point of water and then pumps it through the mats beneath the rink surface. The surface is then sprayed with water, which freezes.

This is how a permanent ice rink is created.

Glycol chillers in dairy processing

A properly designed glycol chiller cools the milk very quickly. This helps to keep its temperature (and bacterial growth) under control as it is transferred from the milking parlour to the insulated tank.

Other applications of the glycol chiller

In addition to the above use cases, glycol units are used in areas such as rubber, plastics, petrochemicals, chemicals, electronics, paper, textiles, pharmaceuticals, air conditioning, etc.

How to select the capacity of a glycol chiller?

To select the capacity of a glycol chiller, pay attention to the type of chiller, required efficiency, type of tank, water flow rate.

What are the types of glycol chillers?

There are two main chiller varieties of glycol chillers to choose from: air-cooled or water-cooled.

Air-cooled glycol chillers use a condenser similar to the radiator in a car.  This has a fan that circulates air through the coolant hose. In most cases, this type of condenser requires an ambient temperature of less than 35 degrees Celsius to operate efficiently.

The only exception is for chillers specifically designed for hot climates.

It is worth noting here that maintenance of air-cooled chillers is more straightforward. In addition, they do not require cooling towers and are easier to install.

Water-cooled glycol chillers, on the other hand, they work similarly but require two stages to complete the thermal transfer. First, heat from the refrigerant vapour enters the condenser water. The heated water then enters the cooling tower, where it loses temperature.

As a general rule, water-cooled chillers are more efficient, which also translates into lower energy costs. They are also more long-lasting and quieter. In addition, they are more effective at maintaining consistent cooling performance.

How to calculate the cooling capacity needed?

To calculate the cooling capacity needed you should use the formula below:

1. Calculate the temperature difference = inlet water temperature (°C) - outlet chilled water temperature (°C) 
2. Calculate the required water flow rate per hour (m³/h) 
3. Based on the results above, calculate the cooling capacity in tonnes = Water flow rate x Temperature difference ÷ 0.86 ÷ 3.517 
4. Oversize the aggregate by 20%. Ideal size in tonnes = tonnes of capacity needed x 1.2

You have just calculated the ideal chiller capacity.

What type of glycol chiller tank to choose?

There are two types of glycol chiller tanks to choose – built-in and external

Glycol chiller with a built-in tank is easier to install. All you have to do is connect the water pipe to the process. But on the other hand, such a chiller has a limited capacity and is not suitable for applications with higher chilled water requirements.

Glycol chiller with an external tank allows you to adapt the capacity of the external tank to your needs. It will fulfil the role of a buffer for higher heat loads and store more chilled water, but its installation is more demanding.

What is the water flow rate in a glycol chiller?

The water flow in a glycol chiller is primarily controlled by the pump. This makes it easy for you to choose one whose flow rate suits your needs.

Glycol chiller or water chiller?

The main difference between glycol chiller and water chiller are their freezing points and heat transfer capabilities.

Pure glycol or a mixture of glycol and water has a significantly lower freezing point than pure water. Consequently, glycol-based chillers are better suited to low-temperature environments.

On the other hand, water has a better ability to retain and conduct heat from the associated process. As a result, the thermal exchange efficiency for a chiller will be higher than for a glycol chiller.

In general, consider the ambient temperature at the installation site and the desired process temperature before selecting the chiller type. Both glycol and water chillers effectively dissipate the high temperatures generated by the production process.

FAQ

At what temperature does glycol cool?

Glycol cools at temperatures down to -60 degrees Celsius (depends on the concentration of the mixture with water).

Why use glycol instead of water?

Glycol instead of water is used in situations where cooling below the freezing point of water is necessary. In addition, glycol is also useful in cold climates because it prevents pipes from freezing.

Is glycol chiller safe?

Glycol chiller is safe, but it should be noted that ethylene glycol is a moderately toxic substance.  Therefore, it is not suitable for drinking water and food processing applications. Propylene glycol, whose toxicity is low, is used in these areas.

Do all chillers use glycol?

No, not all chillers use glycol. Some chillers run on water or other refrigerants.

Can glycol chillers heat?

Yes, glycol chillers can heat. Some are designed to produce both heat and cold.

Summary

The glycol chiller is very similar to other chillers, but thanks to the use of glycol it works well in situations that require better cooling.  Depending on the mixture, it enables effective temperature reduction as low as -60 degrees Celsius.

Therefore, glycol chillers are very often used in alcohol production, food processing and many other places that require strong cooling.

However, be sure to choose the right chiller capacity for your needs. Too small a capacity will not provide the process with the desired temperature, while too large can lead to freezing of the cooling system.