How do vacuum cleaners work?
The science of the humble vacuum cleaner is as simple as using one, writes Jake Port.
The humble vacuum cleaner is one of the handiest household cleaning appliances used today. Its simple yet effective design has done away with having to clean dust and other small particles off surfaces by hand, and turned house cleaning into a more efficient and fairly rapid job. Using nothing but suction, the vacuum whisks away dirt and stores it for disposal.
So how do these household heroes work?
The simplest way to explain how the vacuum cleaner can suck up debris is to think of it like a straw. When you take a sip of drink through a straw, the action of sucking creates a negative air pressure inside the straw: a pressure that is lower than that of the surrounding atmosphere. Just like in space films, where a breach in the spaceship’s hull sucks people into space, a vacuum cleaner creates a negative pressure inside, which causes a flow of air into it.
The vacuum cleaner uses an electric motor that spins a fan, sucking in air – and any small particles caught up in it – and pushing it out the other side, into a bag or a canister, to create the negative pressure. You might think then that after a few seconds it would stop working, since you can only force so much air into a confined space. To solve this, the vacuum has an exhaust port that vents the air out the other side, allowing the motor to continue functioning normally.
The air, however, does not just pass through and get ejected out the other side. It would be very harmful to people using the vacuum. Why? Well, on top of the dirt and grime that a vacuum picks up, it also collects very fine particles that are almost invisible to the eye. If they are inhaled in large enough quantities, they can cause damage to the lungs. Since not all of these particles are trapped by the bag or canister, the vacuum cleaner passes the air through at least one fine filter and often a HEPA (High Efficiency Particulate Arresting) filter to remove almost all of the dust. Only now is the air safe to be breathed again.
The power of a vacuum cleaner is determined not just by the power of its motor, but also the size of the intake port, the part that sucks up the dirt. The smaller the size of the intake, the more suction power is generated, as squeezing the same amount of air through a narrower passage means that the air must move faster. This is the reason that vacuum cleaner attachments with narrow, small entry ports seem to have a much higher suction than a larger one.
There are many different types of vacuum cleaner, but all of them work on the same principle of creating negative pressure using a fan, trapping the sucked-up dirt, cleaning the exhaust air and then releasing it. The world would be a much dirtier place without them.