For the purposes of this article, I'm going to assume that you're familiar with both vacuums and fans. If not, here's a quick primer: A vacuum cleaner sucks air out of a room; it creates a low pressure zone which pulls in higher pressure air from behind it through a tube. This high-pressure air is then pulled into an outlet by means of small blades on the other side of the fan blade (these blades are called rotor blades).
So then, does a fan work in space? The short answer is no—but there's more to it than that!
A fan is a mechanical device that uses a propeller-like device to move air. Fans are used for cooling off computer components, moving air in rooms, and moving air in vacuums.
Note that there's no need for electricity in order for the fan to work. Fans can be powered by both electric motors or hand-powered mechanisms like those found on an accordion or organ.
A vacuum is an empty space that does not have any matter in it. It's a lot like outer space, except you can't see or hear anything from the vacuum because it's empty. A vacuum cleaner sucks up dirt and dust in order to clean your carpet, but it doesn't suck up air. Instead, the vacuum sucks up all of the dirt and dust particles together so they become one big clump of particles that you can easily pick up with a piece of paper or cloth (and then throw away).
If there were no matter in space—no air, water or liquid—then how would birds fly? How would airplanes fly? How would rockets take off into space? These questions all have one answer: fans!
If a fan were inside a vacuum, the fan would not be able to move any air because there would be no air for the blades of the fan to push around.
The blades of a fan are designed to create low pressure zones so that high pressure air can be drawn in. If there is no air and thus no low pressure zone, then there is no force pulling in high pressure air from outside and so nothing will happen when your vacuum turns on.
A fan blade does work by creating a low pressure zone on one side of the blade that pulls in higher pressure air and moves it out of the way, creating more low pressure and pulling in even more high pressure air from behind it.
This creates a vacuum of sorts that makes things move towards the fan blades, which is why stationary objects like dust particles will be blown away by fans.
If there were no air to suck up into this vacuum then there would be nothing for any moving object to push against.
A fan needs air to work. The purpose of a fan is to push around air, and without air that can't be done. A fan's job is to create a low pressure zone: the blades pull in more surrounding air than they push out, creating an area of lower pressure (like the bottom of a hill). When you put your hand over a low pressure zone, you feel lighter than normal because it's easier for you to move there than in other areas where there's higher pressure (like at the top of a hill). But if there is no surrounding air, then there will be no low-pressure regions for your hand to feel lighter than normal.
When you put a fan in a vacuum, the blades will not spin because there is no air for them to move around. The same goes for any other object that needs air to work: turbines, propellers and fans all need it in order to function properly!