Problem 14-65
Hydrogen can cause fire hazards, and hydrogen gas leaking into the surrounding air can lead to
spontaneous ignition with extremely hot flames. Even at a very low leakage rate, hydrogen can
sustain combustion causing extended fire damage. Hydrogen gas is lighter than air, so if a leakage
occurs it accumulates under roofs and forms explosive hazards. To prevent such hazards, buildings
containing sources of hydrogen must have an adequate ventilation system and hydrogen sensors.
Consider a metal spherical vessel, with an inner diameter of 5 m and a thickness of 3 mm,
containing hydrogen gas at 2000 kPa. The vessel is situated in a room with atmospheric air at 1
atm. The ventilation system for the room is capable of keeping the air fresh, provided that the rate
of hydrogen leakage is below 5 µg/s. If the diffusion coefficient and solubility of hydrogen gas in
the metal vessel are 1.5×10-12 m²/s and 0.005 kmol/(m³-bar), respectively, determine whether or
not the vessel is safely containing the hydrogen gas.
