Empire State building was hit, last time I checked it was up.
What about the third world trade center building? Why did it fall? Was there a small jet plane that hit it a few hours later or what?
It has been said the reason for the collapse was due to the fire retardent that was used to coat the beams were not completely covered and thus the heat affected the uncovered parts and caused the collapses. Right!!!!!!!!!!!
It’s really quite simple.
There is a fundamental thermodynamic law, that states:
deltaT = theta * Energy / deltatime
-deltaT is the temperature rise.
- theta is the thermal resistance of the media
- Energy is the total energy contained in the jet fuel
- delta time is the time between the airplane crashed into the building until it collapsed (about 1 hour for the south tower : 3600 seconds)
The energy contained in the fuel tanks can be easily calculated:
Well documented is: 23,980 U.S. gal for a Boeing 767ER. Let’s round it down to 20,000 gallons.
Jet-A fuel has an specific energy 42.8 MJ/Kg, minimum (ref:http://aviation.pertamina.com/files/avia…
Jet-A has a mass of 775.0 to 840.0 kg/m^3 (ibid), which leads to a mass of 58700 kg, which leads to an energy of 2.5 TeraJoules.
Plug that back into fundamental thermodynamic formula #1, and we have a couple of things to consider.
A. If deltaT is only 1000C, then theta must be 1.45*10^-7 degreesC/Watt, a patently ridiculous number (waaaay too low).
Or
B. use a more reasonable value for theta (like 4 for ten meters of air) and see that is is theoretically possible for the temperatures to rise to *way* over 100,000 degrees C in some ‘hot’ spots in the middle.
Granted there were other mechanisms (i.e. smoke mass) to carry heat loads away, but unless you can prove to me that those were the majority heat transport mechanisms *and* the thermal conductivity values were on the order of 10^7, I’ll stick with the good ol’ laws of thermodynamics.
One other point. 1 kiloton of TNT is equivalent to 4.186 TeraJoules of energy. That means that the energy in those fuel tanks was the equivalent to 1/2 a kiloton of TNT. It doesn’t matter if it took 1/10,000th of a second to release (as in a nuclear bomb) or 1 hour, the energy is still *all* there — mostly in the building, mostly in heating up steel to way above it’s melting point.
Simple thermodynamics in action.
.
Steel does not do well in extreme heat. In fact, timber does better than steel in a high heat fire because the heat will char the outside of the wood which then acts like an insulator for a time. Most civil engineers know this.
February 23rd, 2010 - 14:40
Hi. Every one that was hit by a large jet full of fuel at high speed. Or the debris and heat from them.
February 23rd, 2010 - 15:03
Empire State building was hit, last time I checked it was up.
What about the third world trade center building? Why did it fall? Was there a small jet plane that hit it a few hours later or what?
February 23rd, 2010 - 15:36
It has been said the reason for the collapse was due to the fire retardent that was used to coat the beams were not completely covered and thus the heat affected the uncovered parts and caused the collapses. Right!!!!!!!!!!!
February 23rd, 2010 - 16:17
It’s really quite simple.
There is a fundamental thermodynamic law, that states:
deltaT = theta * Energy / deltatime
-deltaT is the temperature rise.
- theta is the thermal resistance of the media
- Energy is the total energy contained in the jet fuel
- delta time is the time between the airplane crashed into the building until it collapsed (about 1 hour for the south tower : 3600 seconds)
The energy contained in the fuel tanks can be easily calculated:
Well documented is: 23,980 U.S. gal for a Boeing 767ER. Let’s round it down to 20,000 gallons.
Jet-A fuel has an specific energy 42.8 MJ/Kg, minimum (ref:http://aviation.pertamina.com/files/avia…
Jet-A has a mass of 775.0 to 840.0 kg/m^3 (ibid), which leads to a mass of 58700 kg, which leads to an energy of 2.5 TeraJoules.
Plug that back into fundamental thermodynamic formula #1, and we have a couple of things to consider.
A. If deltaT is only 1000C, then theta must be 1.45*10^-7 degreesC/Watt, a patently ridiculous number (waaaay too low).
Or
B. use a more reasonable value for theta (like 4 for ten meters of air) and see that is is theoretically possible for the temperatures to rise to *way* over 100,000 degrees C in some ‘hot’ spots in the middle.
Granted there were other mechanisms (i.e. smoke mass) to carry heat loads away, but unless you can prove to me that those were the majority heat transport mechanisms *and* the thermal conductivity values were on the order of 10^7, I’ll stick with the good ol’ laws of thermodynamics.
One other point. 1 kiloton of TNT is equivalent to 4.186 TeraJoules of energy. That means that the energy in those fuel tanks was the equivalent to 1/2 a kiloton of TNT. It doesn’t matter if it took 1/10,000th of a second to release (as in a nuclear bomb) or 1 hour, the energy is still *all* there — mostly in the building, mostly in heating up steel to way above it’s melting point.
Simple thermodynamics in action.
.
February 23rd, 2010 - 17:06
Steel does not do well in extreme heat. In fact, timber does better than steel in a high heat fire because the heat will char the outside of the wood which then acts like an insulator for a time. Most civil engineers know this.