Consul liquefied petroleum gas refrigerators work using the ammonia absorption cooling process to remove heat from an insulated box. This refrigeration process dates to Michael Faraday in 1924 and is older than evaporation refrigeration common in electric refrigerators, as of 2015.
The ammonia absorption cooling process involves heating a mixture of distilled water and anhydrous ammonia using a propane flame. Since ammonia has a lower boiling point than water, it evaporates first, taking along a few water molecules. The design of the system causes the water vapor to condense to a liquid and drip back to the absorption chamber while the ammonia continues to rise through the condenser.
The ammonia cools to form a liquid again. Liquid ammonia enters a chamber to mix with hydrogen gas in a reversible endothermic reaction that absorbs heat from the surrounding area, maintaining the cooler temperature in the refrigerator. The gas continues back to the absorption chamber, and as it mixes with water, it releases hydrogen that rises back into the mixing chamber. The unit then releases the heat outside the refrigerator.
Servel introduced the first LP-gas refrigerators in 1928. At the time, consumers had few choices for refrigeration. Those units and the Consul propane refrigerators require Faraday's discovery to operate.