1. #1
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    Default Info for Compartment fire essay needed

    Hello,

    I am currently working on a research paper and powerpoint presentation for my Fire chemistry class.

    The topic being Stages of fire in a compartment fire setting. I have found numerous PDFs on Flashover and fire behovior in general, but only some on compartment fire behavior. I do have a significant amount of info for the project already, but am still looking for some more. Never have enough right?

    So far two of the best articles are from this site titled "Fire development in a compartment - Part 1 and 2"

    I was still at a loss of certain things I wanted to thro in the essay, but have not found. Example... What temps are occurring on average in the upper smoke layer during the incipient, growth, free burning, and smoldering stages. I have some of these #'s but they are somewhat vague from my textbooks. I was wondering if anyone can point me in the direction of some good solid reoprts on compartment fire development including temperatures, common locations of ignition and any other relevant information.

    Thank you for your help and time. I will check this thread frequently in the hopes of some new info. If you feel tht I should post this thread in another forum or on another site to get more response, please let me know.

    Thanks again,

    Andy Vasquez

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    Some places to look for information:

    fire.nist.gov
    The SFPE Handbook of Fire Protection Engineering
    Introduction to Fire Dynamics - Dougal Drysdale

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    ALso check Dr, Quintere's book.


    When you go to the NIST site, look for information on fire modeling. They have a number of previously modeled fires that will show you graphically the temperature structure in a compartment fire.

    One of the reasons you probably aren't finding concrete numbes is that there are no absolutes. The temps/time will depend a great deal on HRR and fire load., as well as ventilation. Every compartment fire is different.

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    It's a bit scary sometimes how smart Quintere is sometimes...

    To get you started with compartment fires, it was common in my schooling to use 600C at the ceiling for flashover in the average residential compartment with ordinary combustibles. The other number we used was an incident heat flux of 20 kW/m^2 to the floor for flashover. These are very rough numbers but then again, fire dynamics especially where compartment fires are concerned is no where close to an exact science. 20% accuracy is generally considered a success in the field of fire science.

    Also, those numbers both came from Drysdale I believe, in case you were wondering.

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    Quote Originally Posted by FFSmoseley
    It's a bit scary sometimes how smart Quintere is sometimes...

    To get you started with compartment fires, it was common in my schooling to use 600C at the ceiling for flashover in the average residential compartment with ordinary combustibles. The other number we used was an incident heat flux of 20 kW/m^2 to the floor for flashover. These are very rough numbers but then again, fire dynamics especially where compartment fires are concerned is no where close to an exact science. 20% accuracy is generally considered a success in the field of fire science.

    Also, those numbers both came from Drysdale I believe, in case you were wondering.
    I don't know where you got the 20% figure from, but I can pretty much guarantee that you won't have a job for long with an error rate of 80%.

    I am also confused as to who taught you that fire dynamics is "no where close" to an exact science. You have a lot to learn! With the instrumentation available and the analytical tools we use, we have been able to not only understand, but pretty much predict how compartment fires will develop. Remember this...fire is a 100% predictable, mathematically calculable physical phenomenon that will burn exactly the same way every time, given the same set of circumstances. Our problem is that we never have the same set of circumstances. We have to apply our knowldege of fire dynamics to the variables we may encounter when trying to solve a fire protection problem.

    Your heat flux assumption may be low. Heat flux is dependent on compartment size and HRR of the burning materials. Babrauskas uses a heat flux of 35KW/m2 for pre flashover fires and 67KW/m2 for post flashover fires. He also cites potential heat flux of 150KW/m2 in a post flashover atmosphere as being possible. Madrzykowski uses a standard heat flux of 70KW/m2 for post flashover fires in office building settings.

    A standard assumption for these values rarely works. Unless, of course, an 80% error rate is acceptable to you.
    Last edited by GeorgeWendtCFI; 11-15-2005 at 10:06 AM.

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    I was taught 6 credit hours of fire dynamics by Prof. Nick Dembsey. It is from him where I first heard the figure of 20% accuracy.

    Although you are reading that statement wrong. Or perhaps what I typed was poorly worded. When I say 20% accuracy, I mean a general prediction will on average be within 20% of the true value in the field of fire science.

    Quote Originally Posted by GeorgeWendtCFI
    but I can pretty much guarantee that you won't have a job for long with an error rate of 80%.
    I think that one is best left up to my manager

    Quote Originally Posted by GeorgeWendtCFI
    I am also confused as to who taught you that fire dynamics is "no where close" to an exact science. You have a lot to learn! With the instrumentation available and the analytical tools we use, we have been able to not only understand, but pretty much predict how compartment fires will develop. Remember this...fire is a 100% predictable, mathematically calculable physical phenomenon that will burn exactly the same way every time, given the same set of circumstances. Our problem is that we never have the same set of circumstances. We have to apply our knowldege of fire dynamics to the variables we may encounter when trying to solve a fire protection problem.
    I am well aware of everything you have just said and I have a pretty firm grasp as to current instrumentation and analytical tools, though I will not disagree that I have a lot to learn. Again I'll cite Prof. Dembsey and my own experience that fire dynamics is no where close to an exact science. Compared with any other science or engineering discipline common today, save for perhaps meteorology (which face many of the same challenges), fire science is no where near an exact science. As a matter of fact, some of the simplifications we are forced to make would be viewed as downright crude by experts in other fields.

    And the real issue which complicates such a transient and complex phenomena is that minute details often have exponential and larger affects on the dynamics of a combustion reaction. Fire is not a 100% predictable, mathematically calculable phenomena because because it is theoretically impossible to measure the details on a small enough scale without in the process, changing those details.

    Quote Originally Posted by GeorgeWendtCFI
    Your heat flux assumption may be low. Heat flux is dependent on compartment size and HRR of the burning materials. Babrauskas uses a heat flux of 35KW/m2 for pre flashover fires and 67KW/m2 for post flashover fires. He also cites potential heat flux of 150KW/m2 in a post flashover atmosphere as being possible. Madrzykowski uses a standard heat flux of 70KW/m2 for post flashover fires in office building settings.

    A standard assumption for these values rarely works. Unless, of course, an 80% error rate is acceptable to you.
    The criteria for flashover I mentioned was from the Waterman study, and yes it may be a bit low for the average compartment on the verge of flashover. I don't disagree with any numbers or sources you cite for post flashover conditions but as we I think we both can agree, talking about "average" conditions in a post flashover condition compartment fire is even less practical than pre flashover conditions. As far as the fire safety field is concerned, however, heat flux to the floor level is not of little concern in post flashover compartments, at that point heat flux from the vents to adjacent compartments is much more important.

    I couldn't agree more that a standard assumption for these types of values doesn't work for any practical application. However the young man is simply using them for a research paper in a fire chemistry class, and having at least a ballpark figure from a reliable and citable source, I can't imagine would hurt anyone for this purpose. When I say I "used" these values it was and is for no more importance than academic and incidental conversation.

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    Quote Originally Posted by FFSmoseley
    I was taught 6 credit hours of fire dynamics by Prof. Nick Dembsey. It is from him where I first heard the figure of 20% accuracy.

    Although you are reading that statement wrong. Or perhaps what I typed was poorly worded. When I say 20% accuracy, I mean a general prediction will on average be within 20% of the true value in the field of fire science.



    I think that one is best left up to my manager



    I am well aware of everything you have just said and I have a pretty firm grasp as to current instrumentation and analytical tools, though I will not disagree that I have a lot to learn. Again I'll cite Prof. Dembsey and my own experience that fire dynamics is no where close to an exact science. Compared with any other science or engineering discipline common today, save for perhaps meteorology (which face many of the same challenges), fire science is no where near an exact science. As a matter of fact, some of the simplifications we are forced to make would be viewed as downright crude by experts in other fields.

    And the real issue which complicates such a transient and complex phenomena is that minute details often have exponential and larger affects on the dynamics of a combustion reaction. Fire is not a 100% predictable, mathematically calculable phenomena because because it is theoretically impossible to measure the details on a small enough scale without in the process, changing those details.



    The criteria for flashover I mentioned was from the Waterman study, and yes it may be a bit low for the average compartment on the verge of flashover. I don't disagree with any numbers or sources you cite for post flashover conditions but as we I think we both can agree, talking about "average" conditions in a post flashover condition compartment fire is even less practical than pre flashover conditions. As far as the fire safety field is concerned, however, heat flux to the floor level is not of little concern in post flashover compartments, at that point heat flux from the vents to adjacent compartments is much more important.

    I couldn't agree more that a standard assumption for these types of values doesn't work for any practical application. However the young man is simply using them for a research paper in a fire chemistry class, and having at least a ballpark figure from a reliable and citable source, I can't imagine would hurt anyone for this purpose. When I say I "used" these values it was and is for no more importance than academic and incidental conversation.
    Other than your professor (whom I vehemently disagree with on several issues here), can you cite one professional journal where the 20% factor is documented?

    You have continually dismissed the issue of fire modeling. Fire modeling is based on mathematical calculaitons of the fire environment. Fire modeling is well-accepted as a tool in both the fire protection and fire investigation fields. If fire dynamics were not mathematically calculable, there would be no such thing as computer fire model programs.

    As far as academic conversation, it is intellectually dishonest to base a paper or presentation on simply one arguably reliable but citeable source. Babauskas and Madrykowski (sp) are undeniably leaders in the field of fire dynamics and fire ignition. To leave out there values to simplify the assignment, "dumbs it down". If he were in my class, I would interpret that as meaning he did as little research as possible. He would lose a tremendous amount of credit.

    Oh, BTW, yes I do teach in a college fire science program.

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    Quote Originally Posted by GeorgeWendtCFI
    Other than your professor (whom I vehemently disagree with on several issues here), can you cite one professional journal where the 20% factor is documented?
    No, other than Prof. Dembsey I cannot cite a journal or publication where an estimation of average accuracy of values is given, but then again I don't really know of any journal articles that tackle the subject or any subject of such broad scope and scale. It was just an educated guess, nothing more. And I understand you shouldn't give me or any of my educators the benefit of the doubt because you don't know them or me, but I can tell you Prof. Dembsey is very knowledgable and well respected in the field and I certainly take that figure from him as trustworthy.

    Quote Originally Posted by GeorgeWendtCFI
    You have continually dismissed the issue of fire modeling. Fire modeling is based on mathematical calculaitons of the fire environment. Fire modeling is well-accepted as a tool in both the fire protection and fire investigation fields. If fire dynamics were not mathematically calculable, there would be no such thing as computer fire model programs.
    Show me where I have expressly dismissed the issue of fire modeling. I understand very well what fire modeling or more specifically (I get the feeling you're referring to) modern computer fire modeling is based on. The most used and arguably most detailed and versatile fire model at present, FDS, is still based on the principles of computational approximation. With FDS and other CFD models a simluation is broken into cells with uniform properties over which various forms of the conservation of energy are applied, however because of the very nature of these equations (and all the wonderful partial differentials) they are impossible to be solved analytically. The are solved with algebraic approximations that come from CFD. With that basic description of a CFD model (assuming a known HRR) have already been mentioned two large simplifications.

    This without even considering radiation and reradiation models, the changing properties of the changing materials, the need for the Large Eddy Simulation now being widely utilized, and then when you begin to try to model the fire itself, flame propagation and ignition complications arise, small scale radiation and small/large scale interface issues come about, material property uncertainty, the factors are endless.

    Fire models are just another tool in the tool box. They are a great thing but have many limitations and pose a great danger in their over use and over trust.

    Quote Originally Posted by GeorgeWendtCFI
    As far as academic conversation, it is intellectually dishonest to base a paper or presentation on simply one arguably reliable but citeable source. Babauskas and Madrykowski (sp) are undeniably leaders in the field of fire dynamics and fire ignition. To leave out there values to simplify the assignment, "dumbs it down". If he were in my class, I would interpret that as meaning he did as little research as possible. He would lose a tremendous amount of credit.

    Oh, BTW, yes I do teach in a college fire science program.
    No doubt Babrauskas and Madrykowski are among the leading expert in the overreaching field of study of fire dynamics, as are Gunnar Heskestad, Kevin McGratton, Archibald Tewarson, Drysdal, Klote, Milke, Alpert, Zalosh, Harkelroad, DiRis, ... the list goes on and on.

    I certainly wouldn't and haven't recommended using just one source, nor was I claiming I had somehow given a comprehensive list, nor did I suggest he take the values I had given and hault his research there; I was simply attempting to provide a starting point.

    I do respect your opinion a great deal and appreciate the fact you seem to me to be quite the adept educator. All my best professors displayed the same qualities of rigorous analysis and questioning, while taking nothing at face value.

    I was just lending some friendly advice from my education and experience.

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    Quote Originally Posted by GeorgeWendtCFI
    If fire dynamics were not mathematically calculable, there would be no such thing as computer fire model programs.
    And for clarification, I never denied fire dynamics is not mathematically calculable, I took issue with your assertion that is 100% mathematically calculable, which most certainly isn't, as I outlined in my little expose on computer fire modeling.

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    Quote Originally Posted by FFSmoseley
    And for clarification, I never denied fire dynamics is not mathematically calculable, I took issue with your assertion that is 100% mathematically calculable, which most certainly isn't, as I outlined in my little expose on computer fire modeling.
    Expose? Please.

    Once more, I guess we disagree.

    BTW, why don't you check with your professor to find out if hHE has a cite for that 20% figure. I am very interested.

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    Quote Originally Posted by GeorgeWendtCFI
    Expose? Please.
    If it upsets you I'll change my wording.

    Quote Originally Posted by GeorgeWendtCFI
    Once more, I guess we disagree.
    Agreed.

    Quote Originally Posted by GeorgeWendtCFI

    BTW, why don't you check with your professor to find out if hHE has a cite for that 20% figure. I am very interested.
    If you are really dying to know I'll shoot him an email, but otherwise I'll ask him if I happen to need to contact him for some other reason. I haven't had him for a class in two years, and haven't seen him in several months. I wouldn't get so hung up over the 20% figure; he, as I did, used it merely to convey the approximate level of accuracy we could expect to see from our calculations and models. I will tell you right now he does not have a cite for it but was probably based on his personal experience, and he is well qualified to make the statement.

    If you would rather make that judgement for youself, here is the link to his CV, from his own webpage:

    http://users.wpi.edu/~ndembsey/NAD-CV-082005.pdf

    As a matter of fact his exact words were close to "In other sciences they look to be accurate within a half or one percent, almost never more than five. In fire [dynamics] we're happy if we're, you know, 20 or 40% accurate."

    Edit: typos

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    I'm not "dying" to know anything. I am also not doubting the qualifications of your instructor. I simply want to know if there is a source out there stating the 20% figure in print. These types of things have a tendency to pop up in court and I like to be aware of them ahead of time.

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    Quote Originally Posted by Laminar
    Hello,

    I am currently working on a research paper and powerpoint presentation for my Fire chemistry class.

    The topic being Stages of fire in a compartment fire setting. I have found numerous PDFs on Flashover and fire behovior in general, but only some on compartment fire behavior. I do have a significant amount of info for the project already, but am still looking for some more. Never have enough right?

    So far two of the best articles are from this site titled "Fire development in a compartment - Part 1 and 2"

    I was still at a loss of certain things I wanted to thro in the essay, but have not found. Example... What temps are occurring on average in the upper smoke layer during the incipient, growth, free burning, and smoldering stages. I have some of these #'s but they are somewhat vague from my textbooks. I was wondering if anyone can point me in the direction of some good solid reoprts on compartment fire development including temperatures, common locations of ignition and any other relevant information.

    Thank you for your help and time. I will check this thread frequently in the hopes of some new info. If you feel tht I should post this thread in another forum or on another site to get more response, please let me know.

    Thanks again,

    Andy Vasquez
    The fire investigative unit I belong to constucted a modular building 10x12 consisting of 2x4 framing and 1/2 inch drywall and have furnished it with the help of the local Good Will Industries. For training purposes we have conducted live burns using different ignition techniques, for instance, one time we used a paper trailer and another time we set up a senerio for our junior investigators placing an electric iron in the area of origin and using an open flame to set the fire. It was their responsibility to conduct a thorough investigation from the beginning to the end and then submit their findings to the personnel in-charge. Part of this live burn was the placing of operating smoke detectors and two thermal couples, one at the ceiling and one at the floor. The times and temperatures were recorded. If I am not to late you are welcome to the information if you think it will help you in your endeavor.

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