Thanks for your input Myriad. You did help me out.
I have a few more basic questions if you don't mind.
In an insulated environment, such as the WTC rubble piles, a core temperature of 1000C is not out of the ordinary.
Well, I see what you're trying to say, but be careful how you phrase it. "Out of the ordinary" phenomena doesn't mean "unexpected" or "unexplainable" when you're talking about out of the ordinary conditions. I would say that a temperature of 1000C is out of the ordinary. We don't see enormous ignited rubble piles every day. But given that the burning rubble piles were there, I wouldn't regard some regions within them reaching 1000C as unexpected or unexplainable given the known facts.
If any necessary element for hot fires had been missing, then high temperatures would not be expected and the occurrence of high temperatures would mean that something we didn't understand or didn't take into account was going on. But we had: ample
fuel (the entire office contents of the unburned and incompletely burned floors), sufficient conditions for
ignition (tons of already burning fuel at the time of collapse), sufficient
ventilation (the rubble, overall, was slightly porous, not a single solid mass, and there were subway and sewer tunnels providing openings from underneath like the inflow vents of a stove), a sufficiently large volume and sufficient insulation to trap a lot of heat.
How would we be able to determine what temperature would be out of the ordinary?
For example, if I said 1500C was reached, would that seem odd or not out of the ordinary?
To get a precise idea of what temperatures would be expected, we would have to do some very complex calculations or simulations, taking all the above factors into account in a quantitative way. How much fuel, exactly, and how was it distributed through the rubble? How much ventilation in each location, by exactly what paths? This is basically what NIST did in the fire modeling phase of the collapse investigation, for the fires before collapse. Compared to those studies, the rubble plies are in more complex, with less data to go on. (We know, for instance, where all the building structures were before the plane impacts, and by modeling the crashes NIST could make reasonable estimates of where they would be after the crash. But there is to my knowledge no detailed 3-D map of all the layers of the rubble piles just after collapse, and no way to create one that comes to mind, even if the effort after the collapse had been totally focussed on that instead of on search and rescue.)
Had some of the steel actually melted into puddles in the rubble fires, I would not have been surprised (though I would have been surprised if that had happened without making the surface of the rubble piles uninhabitable for a time), so I would regard temperatures up to the melting point of the steel as plausible if the conditions in the piles had been exactly right for it. Temperatures above the melting point of the majority of the steel would be harder to account for, however, because the melting of the steel itself would absorb some heat. (What I said before, about adding heat always increasing the temperature, was simplified for clarity, so I didn't have to write a whole physics book. Sometimes, adding heat to a substance causes a phase change instead of increasing the temperature. If you have ice and water mixed at 0°C, and you add heat, what happens is some of the ice turns to water but the temperature does not rise above 0°C as long as the ice and water stay mixed. The same with melted and unmelted steel.) Also any flowing of melted steel would move heat around -- technically, representing another form of convection and tending to redistribute heat to limit the temperature of those hot spots.
So, if steel started melting in some portion of the rubble, I would expect the temperature to plateau there, at least until all the steel in that hot region had melted. So, I would find 1500°C temperatures, above the melting point of steel, difficult to account for under the known conditions of the rubble piles, and I would expect to see truly melted steel -- not bent I-beams that still look like I-beams, but actual liquid that had flowed and resolidified -- in or under those hot spots afterward.
All of this applies on the relatively large scale. On the small scale, a small piece of material reaching a very high temperature for a short time might be explainable by unusual local conditions -- an airplane oxygen generator or a welder's torch briefly creating intense flame in a contained volume, for instance. An extreme example of this is ordinary sparks -- from hot metal striking concrete, for example. Sparks can easily be over 1500C or even 2000C, but in a very small volume for a very short time.
Respectfully,
Myriad
