Basically title, you always hear “windchill only affects humans” but we use fans to cool things all the time?
In: Physics
If you feel hot and need cooling, then fans help you cool by providing a continuous change of the layer of air that is next to your skin. This takes advantage of two ways to cool something: convective heat loss, where heat is conducted from your skin to the air, and evaporative heat loss, which uses evaporation of sweat from your skin.
Convective heat loss is just a transfer of heat from your skin to the air (or to the water, if you are in water), and if you are continuously changing the warm air that is right next to your skin (warm because it has absorbed heat from your hot skin), with cooler air from elsewhere in the room, then convective heat loss will be more rapid. A bigger temperature difference between your hot skin and the layer of air around it means faster heat transfer.
Evaporative heat loss is extremely efficient, because the phase change from liquid water (skin) to water vapor (evaporated water), which is called evaporation, requires lots of energy, and this energy is taken from your skin in the form of heat. You can experience this by putting a sweaty arm in front of a fan, and it will instantly feel cooler, even if that air is warm, such as air from a window fan on a hot day.
Wind chill does affect objects, in a way. When it is windy, objects lose heat by the convective heat loss mechanism more rapidly than with no wind, but they can never get colder than the air around them. Heat spontaneously flows from a warmer thing to a colder thing, never the other way.
A little breeze on a hot day produces wind chill as well, especially if you are sweating, but we welcome it.
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