In the blog post “How Glycol Concentration Affects Chiller Performance,” we learned what glycol concentration is and how it’s affected. Because commonly used coolants are mixtures of water and ethylene glycol, propylene glycol, or antifreeze. Glycol concentration is commonly referred to as the coolant ratio, which represents the volume ratio between water and glycol in the coolant mixture. This article discusses the impact of an incorrect coolant ratio on industrial chillers.

Decreased Cooling Efficiency

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The specific heat capacity of a glycol-water mixture decreases with increasing glycol concentration. Therefore, when the glycol ratio in a solution is too high, its heat absorption and heat release capabilities decrease. It cannot efficiently absorb heat from the equipment or process, nor can it release it effectively in the evaporator, making it difficult to achieve the desired outlet temperature.
 
In addition, as concentration increases, the viscosity of the coolant increases, slowing its flow through the pipes. This increases the time the coolant remains in the system, reducing the overall circulation efficiency of the system. In other words, less coolant volume passes through the evaporator per unit time, resulting in reduced heat exchange efficiency.

Increased Risk of Freezing

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Water freezes below 0°C, and adding an appropriate amount of glycol can lower the freezing point of a solution. If the glycol content of the coolant is too low, the equipment is at greater risk of freezing in low-temperature environments. This can cause ice to form and clog components flowing through the coolant, or even damage the equipment due to expansion.

Compressor Failure

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If the glycol content of the coolant is too high, its thermal conductivity will decrease. To achieve the set temperature, the system will increase the refrigerant flow rate. However, the coolant cannot effectively transfer heat at the evaporator, and the refrigerant may not fully evaporate, entering the compressor as a mixture of liquid and gas. The compressor cannot compress the liquid, and forced compression can cause severe shock and vibration of the compressor components, even cracking valves, connecting rods, and the casing.

Corrosion or Clogging

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When the coolant concentration is too high, the coolant viscosity increases, and the fluid velocity slows, easily forming deposits in low-velocity areas such as heat exchangers and coils. Furthermore, high glycol concentrations can crystallize at low temperatures, clogging filters, expansion valves, or pipes.
 
 In cooling systems that operate for extended periods or undergo intermittent shutdowns, thick coolant is more likely to form flocculent residue. If the coolant concentration is too low, it can easily corrode the system. Iron and copper oxide particles circulate with the coolant within the system. These particles can clog microchannel heat exchangers and pump impellers.
 
Furthermore, low coolant concentrations can easily breed microorganisms, forming biofilms in the system. This not only clogs pipes but also accelerates acid corrosion. If you notice a decrease in the water flow rate from your equipment or abnormal system temperatures, you may be considering a blockage in the coolant circuit.
 
Furthermore, an improper coolant ratio can cause abnormal bubbles in the liquid. Once these bubbles enter the compressor, they can cause uneven compression, cylinder knocking, and rotor imbalance. This not only affects compressor operation and causes increased noise, but also accelerates wear and shortens its service life.