glycol for chillers

Introduction​
In chiller systems, glycol is a substance of significant importance. Chillers are responsible for removing heat from various environments, whether it’s maintaining comfortable temperatures in buildings or cooling industrial processes. Glycol is added to the chiller’s coolant mixture to enhance its performance and protect the system from potential damage, especially in low – temperature conditions. Understanding the role, types, and proper use of glycol in chillers is essential for ensuring the efficient and reliable operation of these cooling systems.​

The Role of Glycol in Chillers​
Freeze Protection​
One of the primary functions of glycol in chillers is to prevent freezing. Chiller systems often operate in environments where the temperature of the coolant can drop significantly. Without proper protection, the water in the coolant mixture could freeze, causing pipes to burst, components to crack, and ultimately leading to system failure. Glycol lowers the freezing point of the coolant mixture. For example, in a mixture of water and ethylene glycol, as the percentage of ethylene glycol increases, the freezing point of the mixture decreases. A 50:50 mixture of ethylene glycol and water has a freezing point of around -34°C (-29.2°F), compared to the 0°C (32°F) freezing point of pure water. This allows the chiller system to operate safely in cold conditions without the risk of the coolant freezing.​
Corrosion Inhibition​
Glycol also acts as a corrosion inhibitor. In chiller systems, the coolant comes into contact with various metals, such as copper, steel, and aluminum. Over time, exposure to water and oxygen can cause these metals to corrode. Corrosion not only weakens the components but can also lead to the formation of deposits that reduce heat transfer efficiency. Glycol – based coolants contain additives that form a protective film on the metal surfaces, preventing direct contact between the metal and the corrosive elements in the coolant. This significantly extends the lifespan of the chiller system components and helps maintain optimal performance.​
Heat Transfer Enhancement​
Although glycol has a slightly lower heat – transfer coefficient compared to water, when used in the appropriate concentration, it can still contribute to efficient heat transfer. The addition of glycol does not impede the overall heat – transfer process in the chiller significantly. Instead, it enables the system to operate effectively across a wider range of temperatures, ensuring that heat is consistently removed from the environment being cooled and transferred to the heat – rejection medium, whether it’s air or water.​
Types of Glycol Used in Chillers​
Ethylene Glycol​
Ethylene glycol is a commonly used glycol in chiller systems. It has excellent freeze – protection properties and is highly effective at lowering the freezing point of the coolant mixture. Ethylene glycol also offers good heat – transfer characteristics and is compatible with many common materials used in chiller construction. However, it is toxic to humans and animals if ingested. Even small amounts can cause serious health problems, including kidney damage and potentially be fatal. Therefore, when using ethylene glycol in chiller systems, strict safety measures must be in place to prevent accidental spills and ingestion.​

Propylene Glycol​
Propylene glycol is another type of glycol used in chillers, especially in applications where toxicity is a concern. It is considered less toxic than ethylene glycol and is often used in systems where there is a risk of accidental contact with food, beverages, or where the system is located in areas accessible to humans and animals, such as in some commercial buildings or food – processing facilities. Propylene glycol also provides effective freeze protection and corrosion inhibition, although its performance in lowering the freezing point may be slightly less than that of ethylene glycol at the same concentration.​
Glycol Concentration and System Compatibility​
Determining the Right Concentration​
The concentration of glycol in the chiller coolant is crucial. A higher glycol concentration will result in a lower freezing point but may also increase the viscosity of the coolant, reducing its flow rate and potentially affecting heat – transfer efficiency. On the other hand, a lower glycol concentration may not provide sufficient freeze protection. The optimal glycol concentration depends on several factors, including the lowest expected operating temperature of the chiller, the type of glycol used, and the specific requirements of the chiller system. As a general rule, for most applications, a glycol concentration between 30% and 50% (by volume) is commonly used. However, this may vary, and it’s essential to consult the chiller manufacturer’s guidelines for the recommended concentration.​
System Compatibility​
Before using glycol in a chiller system, it’s important to ensure compatibility with the system’s components. Some materials, such as certain types of plastics and elastomers, may degrade or swell when exposed to glycol over time. For example, some older rubber gaskets may not be compatible with glycol – based coolants. Additionally, different glycol types may react differently with certain metals or coatings. It’s advisable to check with the chiller manufacturer or a coolant specialist to confirm that the chosen glycol is suitable for the specific chiller system to avoid any potential compatibility issues that could lead to system failures or leaks.​
Environmental and Safety Considerations​
Environmental Impact​
Both ethylene glycol and propylene glycol can have environmental impacts if not properly managed. Ethylene glycol, due to its toxicity, can be harmful to aquatic life and the ecosystem if it leaks into water sources. Propylene glycol, while less toxic, can still affect the natural balance of water bodies in large quantities. When disposing of glycol – based coolants, it’s important to follow local environmental regulations. In many cases, used glycol – containing coolants need to be collected and processed by specialized waste – management facilities to prevent contamination of the environment.​
Safety Precautions​
When handling glycol, safety should be a top priority. Workers should wear appropriate personal protective equipment (PPE), such as gloves, goggles, and protective clothing, to prevent skin contact and eye irritation. In the event of a spill, it should be cleaned up promptly using absorbent materials, and the contaminated materials should be disposed of properly. For ethylene glycol, in particular, any accidental ingestion should be treated as a medical emergency, and immediate medical attention should be sought.​

Glycol Maintenance and Replacement​
Regular Maintenance​
Regular maintenance of the glycol in a chiller system is essential for its continued effectiveness. This includes monitoring the glycol concentration regularly to ensure it remains within the recommended range. A hydrometer or a refractometer can be used to measure the glycol concentration. Additionally, the coolant should be inspected for signs of contamination, such as the presence of debris, discoloration, or an unusual odor. If any contaminants are detected, the coolant may need to be filtered or replaced.​
Replacement Intervals​
The replacement interval for glycol in a chiller system depends on several factors, including the operating conditions, the quality of the glycol, and the level of contamination. In general, glycol – based coolants should be replaced every 2 – 5 years. However, in harsher operating environments, such as those with high temperatures, high humidity, or frequent cycling, the replacement interval may be shorter. It’s important to follow the chiller manufacturer’s recommendations for replacement to ensure the optimal performance and longevity of the chiller system.​
Conclusion​
Glycol is an indispensable component in chiller systems, providing essential functions such as freeze protection, corrosion inhibition, and contributing to heat – transfer efficiency. Understanding the different types of glycol, their properties, and how to use them correctly is crucial for the efficient and reliable operation of chillers. By paying attention to glycol concentration, system compatibility, environmental and safety considerations, as well as regular maintenance and replacement, users can ensure that their chiller systems perform at their best, providing consistent and effective cooling while minimizing the risk of damage and environmental impact.