Freeze Protection of Closed Loop Systems

Antifreeze is used to freeze protect water based heat transfer fluids - brines

Various types and concentration of antifreeze like

• ethanol
• methanol
• propylene glycol
• ethylene glycol

can be used to freeze protect brines where the temperature in the fluids are below 0^oC (32^oF). Typical advantages and disadvantages for the freeze protection fluids are listed below:

Ethanol

• low corrosiveness
• high flammability if pure
• low toxicity
• high heat transfer capacity
• low viscosity
• moderate cost

Methanol

• low corrosiveness
• high flammability if pure
• high toxicity
• high heat transfer capacity
• low viscosity
• low cost

Propylene Glycol

• low corrosiveness
• low flammability
• low toxicity
• high heat transfer capacity
• higher viscosity
• high cost

Ethylene Glycol

• low corrosiveness
• low flammability
• high toxicity
• lower heat transfer capacity
• higher viscosity
• high cost

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