Monday, May 5, 2014

2.1.3 Buoyancy and Diffusivity

Hydrogen is the smallest and lightest known molecule, and therefore is the “lightest” gas. Hydrogen has only 7 percent of the density of air, which means that a given volume of air will weigh fourteen times as much as the same volume of hydrogen gas at atmospheric pressure.

Because it is so light and the molecules are so small, hydrogen leaking from a vessel rises and diffuses very quickly in air. The rate of diffusion for hydrogen in air is over ten times the rate for gasoline and other fuel vapors (Raj, 1998). This means that leaked hydrogen will quickly dissipate in open air to the point that the mixture is no longer flammable.

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