Coolants

Coolants are fluids used to remove heat from systems and processes, maintaining operating temperatures within safe limits. They are chosen for heat transfer efficiency, stability under operating conditions, and compatibility with system materials.

Common applications include automotive cooling systems, industrial process cooling, and refrigeration or air conditioning systems. In addition, specialized coolants are used in nuclear reactors, metal casting, and high-temperature equipment. Automotive and many industrial systems rely on water with additives to raise boiling points and lower freezing points; glycols such as ethylene glycol or propylene glycol are often mixed with water and corrosion inhibitors to improve performance and safety. Refrigerants in HVAC and heat pump systems act as coolants that absorb heat through phase change. Some high-temperature or niche applications use liquid metals or inert gases as coolants.

Key properties for coolant selection include high heat capacity, sufficient thermal conductivity, suitable boiling and freezing points, and a viscosity that supports efficient flow. Chemical compatibility with pump seals, gaskets, and heat exchangers, along with low toxicity and environmental impact, are important considerations. The selection also depends on operating temperature, pressure, and system design.

Common substances include water, glycol-water blends, mineral or synthetic oils, dielectric fluids for insulating purposes, and refrigerants used in cooling cycles. In specialized settings such as nuclear or metal processing, liquid metals or advanced gases may be employed.

Maintenance and safety involve monitoring for leaks, contamination, and corrosion; using inhibitors and anti-foam agents; proper disposal and recycling; and adherence to regulatory and environmental guidelines, especially for toxic or greenhouse-gas–regulated coolants.