Log in

No account? Create an account
Quick question for any scientists reading... - John [entries|archive|friends|userinfo]

[ userinfo | livejournal userinfo ]
[ archive | journal archive ]

Quick question for any scientists reading... [Jun. 4th, 2006|01:12 pm]
Recently, I saw what I assumed to be a totally bogus question about the destruction of the World Trade Center. Jet fuel (so the claim went) would probably burn at about 600 degrees, not hot enough to melt steel (nor weaken it to the degree required to cause the collapse), and thus, not hot enough to cause the collapse.

My take on this is, this ignores how heat is a *quantity*. A fire burning at 600 degrees is putting out enough heat to cause an object placed in it to reach thermal equilibrium at 600 degrees... but that assumes normal conditions, where heat has somewhere to go.

If there's no place for that heat to go, it will keep building up, raising the temperature. We think of a 600 degree fire as being 600 degrees because there's some level of air flow (because if there isn't, the fire will go out until oxygen is restored). My understanding is, as long as there's combustion going on, there's more heat being put out, and unless there's a place for that heat to go, it's going to build up, and increase the temperature. The question will come down to, how much heat is being added by combustion, minus how much heat is being lost (via smoke, air, radiation, etc..)

So, maybe if you'd put a pool of jet fuel into your barbecue grill, you'd get a 600 degree fire. But put it into an enclosed enough space, that nevertheless has enough oxygen supply, and you'll keep building up the temperature (until the jet fuel is evaporating so fast that the fumes smother the fire because not enough oxygen can reach it, at which point, combustion will stop until it cools down enough for oxygen to reach it again - which is why, when fire fighters vent a fire, it often causes visible flames to start up again.)

Any chemists/physicists/knowledgeable people able to check me on this?

ETA: Comments locked; there's an anonymous commenter who doesn't understand common courtesy.