ELI5 How does something become “pressurized” like in an airplane? What are some other examples?


ELI5 How does something become “pressurized” like in an airplane? What are some other examples?

In: Physics

4 Answers

Anonymous 0 Comments

In order to pressurize something, it has to be a sealed volume. Consider a balloon. Before you blow it up, it is limp because air can freely move in and out of it. There is nothing to block this movement because the opening is not tied off.

However when you squeeze the balloon’s opening over a tank outlet, what you’re doing is sealing the inside of the balloon off from the outside, and “connecting” it to the interior of the tank. When you open the regulator, gas from inside the tank flows from a high pressure space (the inside of the tank) to a lower pressure space (the outside).

Thing is, the balloon, because you’ve sealed it, “gets in the way.” Effectively what you’re doing with pressurizing is forcing more gas into a volume than it would normally have. The gas from the tank fills the balloon and presses outwards — pressure always wants to equalize, or move from high pressure to low pressure. The skin of the balloon traps this higher pressure gas and prevents it from escaping.

However, we all know what happens when you fill the balloon with too much. The skin of the balloon eventually fails — the internal pressure exceeds the material’s ability to contain it. The balloon then ruptures.

This basic principle is in effect whenever you pressurize something. Beer bottles, tires, planes, etc. Submarines as well, but the pressure gradient is flipped. You take that sealed volume and through means of a pump you force more gas into that volume than you’d normally get.

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