How It Works
As Roger says, all marine refrigerators remove heat from a box. And all use a gas refrigerant that's condensed (turned into a liquid) and evaporated (turned back into a gas) at different pressures in a closed system. The heat removal-which causes the icebox to get cold-happens when pressurized liquid refrigerant is allowed to quickly decompress in a long, curved tube in the icebox. The pressure drop in the system causes the liquid to evaporate, and as we all learned in high-school science class (OK, maybe some of us), when a liquid evaporates (boils off into a gas), it absorbs a significant amount of heat, at least enough to keep the beer cold.