How does an electric heating element or a gas flame keep my food cold?
Gas or electric refrigerators operate on the absorption principle. This is a relatively simple method of cooling which uses no moving parts. The cooling unit, which is the maze of tubing you see at the rear of your refrigerator, is where the work is done. The cooling unit is charged with ammonia, hydrogen, water, and sodium chromate.
In a short simple description of the cooling process, the ammonia is liquefied and flows into the hydrogen gas in the evaporator (freezer) where it evaporates rapidly, this is what causes the cooling.