The Basic Cycle
A refrigerator moves heat from the inside of a cabinet to the room. In the vapor-compression design, a compressor raises the pressure of a gas, a condenser lets it release heat and turn to liquid, an expansion device drops its pressure, and an evaporator lets it boil again and absorb heat from the cabinet. The substance that circulates is called the refrigerant. This article follows how the refrigerant and the compressor changed, since those two parts decided whether the machine was safe and affordable enough for a kitchen.
Early Fluids: Effective but Hazardous
The first practical machines of the 1800s used whatever worked. Ether was an early choice, but it is flammable. Ammonia, which Carl von Linde and others used for industrial plants from the 1870s, is an excellent refrigerant with high cooling capacity, but it is toxic and has a sharp smell. That was acceptable in a brewery with trained operators and ventilated engine rooms, much less so in a family kitchen.
Other fluids were used as small machines were developed, including sulfur dioxide, methyl chloride and carbon dioxide. Each had drawbacks. Sulfur dioxide is irritating and can corrode, methyl chloride is flammable and toxic and hard to detect, and carbon dioxide needs very high operating pressures. In the 1920s, reports of accidents from leaking refrigerators in homes contributed to concern in the industry, and manufacturers looked for something safer.
Compressors Get Smaller and Sealed
Compressor design had to change along with the fluid. Early household units used a reciprocating piston compressor, much like a small engine, often belt driven from a separate motor, with a shaft seal where it left the housing. Seals wore out and leaked, and the machine needed servicing.
The key improvement was the hermetically sealed unit, where the motor and compressor sit in one welded container with no external shaft. This kept refrigerant in and moisture out, and reduced noise and maintenance. Sealed units became common in the late 1920s and 1930s, and small electric motors made them practical. Later, rotary and scroll compressors were developed for smaller sizes and greater efficiency. Together with better insulation and thermostats, these changes reduced running costs.
The Freon Era
In the late 1920s, researchers at General Motors, including Thomas Midgley Jr., with colleagues such as Albert Henne and Robert McNary, developed a family of chlorofluorocarbons (CFCs). The best known, dichlorodifluoromethane, was sold under the trade name Freon-12 and was introduced around 1930. It was not flammable and had low toxicity in ordinary conditions, and it worked well at moderate pressures. A joint company of General Motors and DuPont began producing it.
CFCs made home refrigeration much safer and quickly became standard across household refrigerators and, later, air conditioners and aerosol sprays. This was a major success story for industrial chemistry of the time, and it was widely judged a safety improvement. Its later environmental consequences were not known.
The Ozone Problem
In 1974, Mario Molina and F. Sherwood Rowland published research suggesting that CFCs released into the atmosphere could break down in the stratosphere and damage the ozone layer. The discovery of the Antarctic ozone hole in the mid-1980s added urgency. In 1987, the Montreal Protocol set a schedule for phasing out ozone-depleting substances, and it has been revised several times since. CFCs were replaced first by hydrochlorofluorocarbons (HCFCs), which are less harmful to ozone but still not benign, and then by hydrofluorocarbons (HFCs), which do not harm ozone.
HFCs, however, are strong greenhouse gases. A later amendment to the protocol, agreed in 2016 in Kigali, set out a gradual reduction in their use. Researchers and manufacturers have since turned to alternatives, including hydrocarbons such as isobutane, which is common in modern household refrigerators in many countries, and newer synthetic fluids with lower warming effect. Hydrocarbons are flammable, so charges are kept small and designs are controlled for safety.
Common Threads
The history of refrigerants shows a repeating pattern:
- A fluid is chosen because it works and is available.
- Its problems appear in use, such as toxicity, flammability or leaks.
- A replacement solves those problems but introduces new, sometimes unforeseen ones.
Ammonia, ironically, is still used widely in industrial plants and cold storage, where trained staff and good design manage its risks. Carbon dioxide has also returned in some commercial systems, using modern high-pressure components that were not available a century ago.
Beyond the Fluid
Compressor and fluid development also interacts with other parts of the machine. Refrigerant choice affects oil selection, tubing materials, seals and efficiency. Better motors, controls and insulation have cut the energy use of a typical household refrigerator substantially over the decades, though exact figures vary by region and model. For the origins of the compressor design itself, see the account of absorption refrigeration, which developed in parallel and uses a different method to avoid the mechanical compressor altogether.
Throughout, the refrigerator is a reminder that an appliance is only as good as the working fluid inside it, and that choices made for safety in one decade can create new questions in the next.