Catalysis

Vapor-compression refrigeration

Gas compressor

Engineering

Ecology

Biology

Global-warming potential

Flammable liquid

Propane

Waste management

Mechanical engineering

Greenhouse gas

Organic chemistry

Isobutane

Process engineering

Environmental science

Chemistry

Refrigeration

Refrigerant

Air conditioning

Science

The high global warming potential of current refrigerants in cooling equipment based on the vapor-compression cycle has triggered a major effort to find and implement more environmentally benign alternatives. Here, we review the basics of the vapor-compression cycle together with the safety, environmental, and thermodynamic constraints that have led to the current and next generation of refrigerants. The development of new fluids has focused on fluorinated olefins, known as hydrofluoroolefins (HFOs), and blends that contain HFOs. Many of these are slightly flammable, presenting trade-offs between safety and environmental considerations. Engineers also have options with a resurgence of the “natural refrigerants” (ammonia, carbon dioxide, propane, and isobutane). Innovative system designs that reduce the required quantity of refrigerant may allow a wider choice of refrigerants.

New refrigerants and system configurations for vapor-compression refrigeration