Air coolers and room fans

A fan does not cool a room. It moves air, and moving air feels cooler on skin — which is already a lot, but it stops the moment you step out of the stream. A thermometer in the room does not shift by a tenth of a degree.

A water cooler does something else. Air passes through a damp filter, the water evaporates, and evaporation consumes heat. Perceived temperature genuinely drops by two to four degrees in a modest volume. It is not air conditioning: there is no compressor and no exhaust, so no heat is dumped outside.