Which refrigeration technique often relies on cooling from external sources?

Evaporative cooling is a refrigeration technique that often relies on cooling from external sources, particularly water. This method takes advantage of the natural process of water evaporation to dissipate heat. When water absorbs heat from the surrounding environment, it transitions from a liquid to a vapor, which can lead to a significant drop in temperature in the air. This cooling is typically enhanced by introducing airflow over water-saturated surfaces, allowing the evaporation process to occur more efficiently.

In contrast to other techniques, evaporative cooling is highly effective in hot and dry conditions, where it can significantly reduce the temperature of the air without the need for mechanical cooling systems. This reliance on external water sources for the cooling effect is a defining characteristic of evaporative cooling systems, differentiating them from direct refrigeration, steam refrigeration, and recirculating refrigeration, which utilize different principles of thermodynamics and typically do not depend on environmental water sources in the same manner.