How can fans cool water from room temp to below ambient?

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The fans are just blowing 75 degree air at 75 degree water so how does the water end up below 75? And is there a limit to how low it could go?

In: Physics

2 Answers

Anonymous 0 Comments

Water absorbs a certain amount of energy/heat when it evaporates. Heat gets used up when it breaks the bonds holding water molecules together as a liquid.

In principle as long as the air is dry you can pretty much indefinitely keep cooling. The air can only hold so much water though.

Anonymous 0 Comments

A fan by itself cannot cool below ambient temperature, if anything, it heats up the air due to electrical resistance of the fan motor.

Evaporative coolers take advantage of the fact that water absorbs heat in order to evaporate. So basically they operate like humidifiers and introduce humidity in the airflow of the fan. The water absorbs the heat, causing the airflow from the unit to be more cool than the intake air. This only works in very dry climates. If the ambient humidity is high, it will not work.

It’s not the fans that cool the water, rather it’s the water that cools the air. This is why it cools off outside after it rains. It’s not just because of the cloud cover blocking the sun, it’s also because the rain begins to evaporate and takes heat with it.