Thursday, November 29, 2007

Jet Fuel Made the WTC Fires Cooler

People assume that the jet fuel which ignited the fires in the Twin Towers made the fires quite hot. However, Thomas Eager, a Professor of Materials Engineering and Engineering Systems at MIT and a defender of the official story explains that the jet fuel actually made the fires cooler:
" . . . the fact that there were 90,000 L of jet fuel on a few floors of the WTC does not mean that this was an unusually hot fire. The temperature of the fire at the WTC was not unusual . . . .

In combustion science, there are three basic types of flames, namely, a jet burner, a pre-mixed flame, and a diffuse flame. A jet burner generally involves mixing the fuel and the oxidant in nearly stoichiometric proportions and igniting the mixture in a constant-volume chamber. Since the combustion products cannot expand in the constant-volume chamber, they exit the chamber as a very high velocity, fully combusted, jet. This is what occurs in a jet engine, and this is the flame type that generates the most intense heat.

In a pre-mixed flame, the same nearly stoichiometric mixture is ignited as it exits a nozzle, under constant pressure conditions. It does not attain the flame velocities of a jet burner. An oxyacetylene torch or a Bunsen burner is a pre-mixed flame.

In a diffuse flame, the fuel and the oxidant are not mixed before ignition, but flow together in an uncontrolled manner and combust when the fuel/oxidant ratios reach values within the flammable range. A fireplace flame is a diffuse flame burning in air, as was the WTC fire.

Diffuse flames generate the lowest heat intensities of the three flame types.

If the fuel and the oxidant start at ambient temperature, a maximum flame temperature can be defined. For carbon burning in pure oxygen, the maximum is 3,200°C; for hydrogen it is 2,750°C. Thus, for virtually any hydrocarbons, the maximum flame temperature, starting at ambient temperature and using pure oxygen, is approximately 3,000°C.

This maximum flame temperature is reduced by two-thirds if air is used rather than pure oxygen. The reason is that every molecule of oxygen releases the heat of formation of a molecule of carbon monoxide and a molecule of water. If pure oxygen is used, this heat only needs to heat two molecules (carbon monoxide and water), while with air, these two molecules must be heated plus four molecules of nitrogen. Thus, burning hydrocarbons in air produces only one-third the temperature increase as burning in pure oxygen because three times as many molecules must be heated when air is used. The maximum flame temperature increase for burning hydrocarbons (jet fuel) in air is, thus, about 1,000°C—hardly sufficient to melt steel at 1,500°C.

But it is very difficult to reach this maximum temperature with a diffuse flame. There is nothing to ensure that the fuel and air in a diffuse flame are mixed in the best ratio. Typically, diffuse flames are fuel rich, meaning that the excess fuel molecules, which are unburned, must also be heated. It is known that most diffuse fires are fuel rich because blowing on a campfire or using a blacksmith’s bellows increases the rate of combustion by adding more oxygen. This fuel-rich diffuse flame can drop the temperature by up to a factor of two again. This is why the temperatures in a residential fire are usually in the 500°C to 650°C range. It is known that the WTC fire was a fuel-rich, diffuse flame as evidenced by the copious black smoke. Soot is generated by incompletely burned fuel; hence, the WTC fire was fuel rich—hardly surprising with 90,000 L of jet fuel available. Factors such as flame volume and quantity of soot decrease the radiative heat loss in the fire, moving the temperature closer to the maximum of 1,000°C. However, it is highly unlikely that the steel at the WTC experienced temperatures above the 750–800°C range."
Indeed, jet fuel can only burn at a maximum temperature of 599 degrees Fahrenheit under normal conditions (other than a controlled burn using a high-oxygen mixture).

Obviously, the jet fuel was a source of fuel, and so contributed to the ignition and spreading of the fire in the first place. However, there was actually very little jet fuel in the overall scheme of things. Moreover, that jet fuel and office supplies were the sources of fuel for the fire almost guaranteed that it would be a fuel-rich, diffuse-flame fire, which burns cool.

While the title may be slightly flip, the purpose of this essay is merely to show that jet fuel -- contrary to most people's assumption -- would not have created a hot fire. See this.

Finally, it is true that the soot from the jet fuel and other burning hydrocarbons may have raised the temperature somewhat. However, as Professor Eager points out, the fact that it was a fuel-rich fire -- at least while the jet fuel was still burning -- decreased the temperature of the fire "by a factor up to two", which would more than offset the increase due to reduction of radiative heat loss. Again, the bottom line is that the WTC fires were not very hot.




9 Comments:

Blogger Melissa said...

What does the professor think caused the building to fall? Why does he think they fell into the path of greatest resistance? How does he explain the speed at which they fell? I would love to hear his explanation.

11:37 PM  
Blogger Melissa said...

Errrr then why does he think the buildings fell. Can he explain why they fell into the path of greatest resistance? What does he say about the speed of the fall?

11:38 PM  
Blogger Brian Adams said...

World first company of an elite group of specialists and pioneers in the private jet services industry. We provide you luxury executive flight experience that is based on superior safety.

3:25 AM  
Blogger b. j. edwards said...

Yes, we are well acquainted with your claims that fires could not possibly have contributed to softening of the steel, that they could not have possibly exceeded certain temperatures, and therefore the towers should not have collapsed because of the crash damage and resulting fires.

Unfortunately for your claims, GW, physical evidence is cumulative. The scientific method does not allow you to ignore inconvenient evidence as you might, for instance, try to do in a trial.

You are still faced with the daunting task of dealing with the fact that the burden of proof rests squarely on your shoulders, GW, to refute all of that evidence and bring a plausible explanation to the table which can explain that evidence and the observations.

We note, again, that no evidence of explosives has ever been found in any of the numerous independent chemical analysis of the dust starting in October 2001.

Once again, you are left in the same place with the same responsibilities to make a case that have studiously tried to avoid all these years, GW.

6:53 AM  
Blogger George Washington said...

b. j. edwards,

You may wish to ask these military leaders, world-class scientists, 9/11 commissioners, congress people, structural engineers, architects, and others -- including psychologists and psychiatrists -- about government complicity.

Thank you in advance for actually looking at what they are saying.

10:07 AM  
Blogger Liberality said...

love your blog and have added you to my blogrool. my interest in 911is personal because we lost family in this terrorist attack. i've always thought the entire senario stank to high heaven.

8:35 PM  
Blogger b. j. edwards said...

I guess I have to repeat the answer for you, GW. Perhaps you should take your blinders off:

Yes, we are well acquainted with your claims that fires could not possibly have contributed to softening of the steel, that they could not have possibly exceeded certain temperatures, and therefore the towers should not have collapsed because of the crash damage and resulting fires.

Unfortunately for your claims, GW, physical evidence is cumulative. The scientific method does not allow you to ignore inconvenient evidence as you might, for instance, try to do in a trial.

You are still faced with the daunting task of dealing with the fact that the burden of proof rests squarely on your shoulders, GW, to refute all of that evidence and bring a plausible explanation to the table which can explain that evidence and the observations.

We note, again, that no evidence of explosives has ever been found in any of the numerous independent chemical analysis of the dust starting in October 2001.

Once again, you are left in the same place with the same responsibilities to make a case that have studiously tried to avoid all these years, GW.

6:46 AM  
Blogger cm2dogs said...

great explaination covering combustion charcteristics and
relitive tempature vairiations this is the positive information we need to move forward in what is otherwise a very difficult task,finding truth!..in a shit storm ...

11:50 PM  
Blogger Woozle said...

This is the only substantial claim in b.j.'s post, as far as I can tell:

"We note, again, that no evidence of explosives has ever been found in any of the numerous independent chemical analysis of the dust starting in October 2001."

...and it's untrue. Off the top of my head, I can think of at the following evidence, even if we're strictly talking about the debris (which isn't the only evidence):

* diagonal cuts in the girders, a signature of thermite cutting (and not a signature of anything else)
* chemical signature of thermite found in dust sampled shortly after the disaster
* traces of sulfur in the steel cuts (sulfur is commonly used with thermite to reduce the steel's melting temp)

So... cut it with the ad-hominem and hand-waving. If you've got some real counter-arguments, please spill them so we can all see how bogus the "inside job" argument is really is.

Otherwise, you're just making it sound more plausible by offering only pathetic and insubstantial counter-arguments.

(Also... somebody please delete the spam from "brian adams"...)

4:29 PM  

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