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Thread: Dust Collection in Basement below Shop

  1. #31
    Join Date
    Feb 2013
    Location
    Tippecanoe County, IN
    Posts
    495
    Quote Originally Posted by Thomas Wilson View Post
    ...I was up this morning at 5am programming the intersection of the fan and system loss curves in Mathematica for my planned dust collection system. This is the fun part for me...
    If you mean that mathematics is more fun than hanging ductwork I couldn't agree more!

    I'd like to hear more about how you use Mathematica for this. You're not doing a full CFD simutation, are you? fwiw, I normalize the flow to a convenient value and then use the square of that as a variable. The fan curve then straightens and of course the system curve becomes a straight line. The solution is then just a linear equation and some arithmetic. With the right normalization value it's easy to do a quick mental calculation for a sanity check.
    Beranek's Law:

    It has been remarked that if one selects his own components, builds his own enclosure, and is convinced he has made a wise choice of design, then his own loudspeaker sounds better to him than does anyone else's loudspeaker. In this case, the frequency response of the loudspeaker seems to play only a minor part in forming a person's opinion.
    L.L. Beranek, Acoustics (McGraw-Hill, New York, 1954), p.208.

  2. #32
    Quote Originally Posted by David L Morse View Post
    If you mean that mathematics is more fun than hanging ductwork I couldn't agree more!

    I'd like to hear more about how you use Mathematica for this. You're not doing a full CFD simutation, are you? fwiw, I normalize the flow to a convenient value and then use the square of that as a variable. The fan curve then straightens and of course the system curve becomes a straight line. The solution is then just a linear equation and some arithmetic. With the right normalization value it's easy to do a quick mental calculation for a sanity check.
    Ha! It is bit more fun. Actually, I just chose Mathematica because it know it has the Lambert functions for an approximation to the Colebrook formula. I basically use it as a fancy interactive calculator that stores my steps. Then, it is easy to go back and change a parameter and have the whole notebook update. I was going to experiment numerically to see the range of values that I might get depending on a conservative or nominal loss factors for fittings. One nice thing about a Mathematica Notebook is that it is relatively easy to enter formatted equations that print like LaTex (if I take the time to do it) so the notebook resembles a typeset document. It is very readable. I could do the same calculations in Matlab or Excel, but the programming is not so pretty.

    No 3D CFD just yet. The work for that would be in setting up the geometry for the boundaries. I have thought about using it to calculate loss factors for a wye with one branch blocked downstream. I haven't found that flow situation for a wye fitting in any table. I am currently just using a 45 elbow using a loss factor of about 0.2. I will try some other values.

    I did not finish programming. A friend came up to see the shop yesterday. He left me with a piece of molding to copy for a kitchen remodel in an old house. The molding looks as if it was made with a Stanley 45 molding plane but the cutter had been resharpened many times into an unrecognizable contour. I can match it with a bead bit and an ogee bit and sandpaper. Word of my shop being available again soon has apparently spread.

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