Külmutusaineet

Külmutusaineet, known in English as refrigerants, are working fluids used in refrigeration and air conditioning systems. They undergo a cycle of evaporation and condensation, absorbing heat in one part of the system and releasing it in another. This thermodynamic process is fundamental to how refrigerators, freezers, and air conditioners function.

Historically, early refrigerants included ammonia, sulfur dioxide, and methyl chloride. However, due to toxicity and flammability concerns, these were largely replaced by chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) in the mid-20th century. While less toxic, CFCs and HCFCs were later found to be highly damaging to the Earth's ozone layer. The Montreal Protocol, an international treaty, mandated their phase-out.

Current refrigerants primarily consist of hydrofluorocarbons (HFCs) and hydrofluoroolefins (HFOs). HFCs do not deplete the ozone layer but many have a high global warming potential (GWP). HFOs are a newer generation of refrigerants designed to have very low GWPs, addressing environmental concerns. Other refrigerants in use or under development include natural refrigerants like ammonia, carbon dioxide, and hydrocarbons, each with their own advantages and disadvantages regarding safety, efficiency, and environmental impact. The choice of refrigerant depends on the specific application, regulatory requirements, and desired performance characteristics.