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Jet Fires (Chamberlain Model)

  1. Dec 19, 2008 #1
    If this has been placed in the wrong forum, please move as appropriate. Thanks.

    I am trying to get to grips with modelling fires using the Chamberlain method, and have guidance from the “Yellow Book”, which can be viewed here: www.vrom.nl/get.asp?file=Docs/milieu/2005_PGS2_GeleBoek.pdf

    In this book on page 6.50 (601 in Acrobat) it described the modelling of jet flames. Then on page 6.97 (648 in Acrobat) it shows a worked calculation ultimately resulting in the heat flux from the fire, I can follow most of this, but I don’t see where the following comes from:

    In Step 25 and 27 he uses a value of distance of 46.7m, which had not previously been referred to, but then in 27 when he substitutes this value into the equation it seems to change to become 139.5658m which I would have expected to be used. Is the 46.7m a mistake?

    The same is true at the end (in step 30) he uses a distance of 49.8m, but all his previous calculations have not taken this value into account, is this a mistake?

    Regardless, when I follow this through with his numbers I naturally get the same results as him.

    The main point I ask for help with is in the final examples given on page 8.13 (787 in Acrobat). When I work through this I simply cannot get even close agreement with his results for q’’. Firstly on page 8.15 (789 in Acrobat) under inputs he states Thetaj=0, but that b*sin(thetaj)=5. This is obviously not correct since anything*sin(0)=0. He also makes reference to a thetajv, I considered the possibility of a typographical error rendering one of the thetaj’s to be a thetajv, but still no agreement. When I work backwards through the calculations and find the value of the theta’s required to give the alpha, b, Rl etc values he has given for the outputs the values of theta required to do this are over 100degrees. He has already stated that thetaj<=thetajv<=90.

    Can anyone help me get to a solution in agreement with the “Yellow book”. Thanks for your help.

    P.S. I have lists of my numbers for each stage of the calculation if you wish to view them for inspiration. If you want them, just reply saying so.

    Regards

    neorich
     
  2. jcsd
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