ethylene glycol for chillers

Chillers play a crucial role in maintaining optimal temperatures in various industrial, commercial, and even some residential applications. In many chiller systems, ethylene glycol is added to the water – based coolant. This addition significantly modifies the properties of the coolant, making it suitable for a wider range of operating conditions.​

Properties of Ethylene Glycol​
Freezing Point Depression​
One of the most notable properties of ethylene glycol is its ability to lower the freezing point of water. Pure water freezes at 0°C (32°F). When ethylene glycol is added, the freezing point of the resulting mixture drops significantly. For example, a 30% ethylene glycol – water solution has a freezing point of around -15°C (5°F), and a 50% solution can have a freezing point as low as -37°C (-35°F). This property is essential in chillers operating in cold environments or in applications where sub – zero temperatures are encountered.​
Boiling Point Elevation​
Ethylene glycol also raises the boiling point of water. Pure water boils at 100°C (212°F) at standard atmospheric pressure. A 50% ethylene glycol – water mixture has a boiling point of approximately 107°C (225°F). This increased boiling point helps prevent the coolant from boiling and vaporizing under high – temperature operating conditions within the chiller, ensuring continuous and reliable operation.​
Viscosity​
Ethylene glycol has a higher viscosity than water. As the concentration of ethylene glycol in the water – based coolant increases, the viscosity of the mixture also rises. Higher viscosity can affect the flow characteristics of the coolant within the chiller pipes. If the viscosity is too high, it can increase the pumping power required to circulate the coolant, leading to higher energy consumption. However, within an appropriate concentration range, the impact on flow can be managed, and the benefits of ethylene glycol’s other properties outweigh this potential drawback.​

Heat – Transfer Properties​
Ethylene glycol has reasonable heat – transfer capabilities. Although its specific heat capacity is lower than that of water (the specific heat capacity of water is 4.186 J/g°C, while that of ethylene glycol is about 2.42 J/g°C), when mixed with water in a chiller system, it still contributes to effective heat transfer. The combination of ethylene glycol and water can transfer heat efficiently between the chiller’s components, such as the evaporator and the condenser, helping to maintain the desired cooling effect.​
Functions of Ethylene Glycol in Chillers​
Antifreeze Protection​
In regions with cold climates or in industrial processes where the chiller coolant may be exposed to sub – zero temperatures, ethylene glycol acts as an antifreeze. Without it, the water in the chiller could freeze. Frozen water expands, which can cause significant damage to the chiller’s pipes, heat exchangers, and other components. By preventing freezing, ethylene glycol ensures the integrity of the chiller system and allows for continuous operation even in cold conditions.​
Extended Operational Temperature Range​
The combined effect of freezing point depression and boiling point elevation by ethylene glycol extends the operational temperature range of the chiller. This is beneficial in applications where the chiller may experience both high – temperature loads during peak operation and low – temperature conditions during off – peak or standby periods. For example, in a data center located in a region with wide temperature variations, the chiller with an ethylene glycol – water mixture can effectively cool the servers during hot summer days and prevent freezing during cold winter nights.​
Corrosion Inhibition (with Additives)​
When used in chiller systems, ethylene glycol is often formulated with corrosion inhibitors. Metals in the chiller, such as copper, iron, and aluminum, can corrode when in contact with water. Corrosion can lead to leaks, reduced heat – transfer efficiency, and ultimately, system failure. The corrosion inhibitors in the ethylene glycol – based coolant form a protective film on the metal surfaces, preventing or reducing the rate of corrosion. This helps to extend the lifespan of the chiller components and maintain the overall performance of the system.​
Advantages of Using Ethylene Glycol in Chillers​
Cost – Effectiveness​
Ethylene glycol is relatively inexpensive compared to some other specialized antifreeze or heat – transfer fluids. Its wide availability and cost – effectiveness make it a popular choice for chiller applications, especially in large – scale industrial and commercial installations where the volume of coolant required is substantial.​

Compatibility with Chiller Components​
Ethylene glycol – water mixtures are generally compatible with most common materials used in chiller construction, including metals, plastics, and elastomers. This compatibility ensures that the coolant does not cause chemical reactions or degradation of the chiller components, allowing for long – term and reliable operation.​
Well – Studied and Established Technology​
The use of ethylene glycol in chiller systems has been well – studied over many years. There is a vast amount of knowledge and experience available regarding its properties, performance, and handling. This makes it easier for engineers and technicians to design, operate, and maintain chiller systems using ethylene glycol – based coolants, reducing the risk of errors and ensuring optimal performance.​
Considerations When Using Ethylene Glycol in Chillers​
Specific Heat Capacity Impact​
As mentioned earlier, ethylene glycol has a lower specific heat capacity than water. This means that for a given mass and temperature change, an ethylene glycol – water mixture can absorb or release less heat compared to pure water. In chiller systems where high cooling capacity is crucial, the lower specific heat capacity of the mixture may require larger volumes of coolant to achieve the same cooling effect. Engineers need to carefully calculate and balance the ethylene glycol concentration to ensure that the chiller can meet the cooling load requirements while still providing adequate freeze protection.​
Toxicity​
Ethylene glycol is toxic if ingested. It can cause serious health problems, including kidney damage and even death. In chiller systems, proper safety measures must be in place to prevent leaks and spills. Regular inspections of the chiller pipes, connections, and components are necessary to detect and repair any potential leaks promptly. In case of a spill, appropriate cleanup procedures should be followed to minimize the risk of exposure to humans and the environment. Additionally, warning signs should be posted in areas where the chiller system is located to alert personnel to the presence of toxic coolant.​
Concentration Optimization​
Determining the optimal concentration of ethylene glycol in the chiller coolant is crucial. A higher concentration of ethylene glycol provides better freeze protection but also increases viscosity and further reduces the specific heat capacity. A lower concentration may not offer sufficient freeze protection in cold conditions. The concentration needs to be adjusted based on the lowest expected temperature in the chiller’s operating environment, the required cooling capacity, and the pumping capabilities of the system. Specialized software or tables are often used to calculate the appropriate ethylene glycol concentration for a given set of operating conditions.​
Safety Measures for Handling Ethylene Glycol in Chillers​
Personal Protective Equipment (PPE)​
Personnel working with chiller systems containing ethylene glycol should wear appropriate PPE. This includes gloves, safety glasses, and protective clothing. Gloves made of materials resistant to ethylene glycol, such as nitrile gloves, should be worn to prevent skin contact. Safety glasses protect the eyes from potential splashes. Protective clothing, such as coveralls, helps to prevent the coolant from coming into contact with the body.​
Spill Response​
In the event of a coolant spill, a well – defined spill response plan should be in place. Absorbent materials, such as spill kits containing absorbent pads and booms, should be readily available. The spilled ethylene glycol should be contained and cleaned up promptly to prevent it from spreading. The cleanup materials should be disposed of properly in accordance with local environmental regulations.​
Storage and Handling​
Ethylene glycol should be stored in a cool, well – ventilated area away from sources of ignition and heat. Storage containers should be tightly sealed to prevent evaporation and contamination. When adding ethylene glycol to the chiller system or performing maintenance tasks, proper handling procedures should be followed. This includes using appropriate transfer equipment and ensuring that the area is well – ventilated to avoid the buildup of vapors.​
In conclusion, ethylene glycol is a valuable component in chiller systems, offering antifreeze protection, extended operational temperature ranges, and other benefits. However, its use requires careful consideration of factors such as specific heat capacity, toxicity, and concentration optimization. By following proper safety measures and engineering principles, ethylene glycol can be effectively used to enhance the performance and reliability of chiller systems in a wide range of applications.