Which refrigerant is commonly used in HVAC systems?

The correct answer reflects the use of chlorofluorocarbons (CFCs) in HVAC systems, specifically in older models. CFCs were widely used as refrigerants due to their efficient thermodynamic properties and stability at environmental conditions. They function effectively in heat transfer processes within air conditioning and refrigeration systems.

Over time, however, research has shown that CFCs contribute significantly to ozone layer depletion, leading to regulatory actions banning their production and use. Consequently, many systems are being updated to use safer and more environmentally friendly alternatives, such as hydrofluorocarbons (HFCs) or natural refrigerants. Understanding this context is crucial for recognizing historical trends in refrigerant usage and the shift toward more sustainable practices in HVAC technology.

Other options refer to terms or substances that are either outdated or not specific refrigerants. R12 is a specific type of CFC, commonly known as dichlorodifluoromethane, which has also been phased out. Freon is a brand name historically associated with refrigerants and to some extent can refer to multiple types, including those that are now prohibited. BTU is a measurement of energy rather than a refrigerant itself. This distinction is important in understanding the mechanisms and