LDM Student

  • Member since Apr 29th 2017
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  • LDM

    Replied to the thread Clearance Items.
    Post
    (Quote from Paradigmnoia)




    What can be the advantage of coating the dogbone with zirconium oxide paint ?
    It beats me ! But I am open to any suggestion.


    Could it be that the construction of the dogone started with a tube where the heating coils where…
  • LDM

    Post
    THHuxleynew  



    Finally found some time again to comment on your last post.


    OK, so I still want to look at this properly, and that must wait later.
    But:
    I expect the calculation with ridges to be comparable with the calculation from a surface area
  • LDM

    Post
    THHuxleynew

    I've been a bit busy with other stuff, still am, and don't want to post properly till I have it sorted out fully.


    Same for me, figuring out these issues takes time

    But, yes, I agree with you. In fact if the reactor is 10mm and the fins
  • LDM

    Post
    Paradigmnoia

    To keep the correct version short, the following is my summarized position:
    Each time a ray impinges on an opposite fin (or any other surface), the radiant power is absorbed directly proportional to that surface emissivity (which is the
  • LDM

    Post
    (Quote from Paradigmnoia)



  • LDM

    Post
    (Quote from Paradigmnoia)


    Some thoughts, I might be wrong, if so you can correct me.

    Kirchhoffs law is valid under thermal equilibrium, being that the object and it's environment have the same temperature. That also means that all parts of the object…
  • LDM

    Post
    THHuxleynew

    THH,

    Can you now agree with me, based on my earlier post, that


    A. The ratio of the area with fin to the ratio of the bare tube is not sqrt(2) for fins with a 90 degree angle between them

    B. The ratio of the area with fins compared to…
  • LDM

    Post
    (Quote from Alan Fletcher)


    Thanks Allan for posting your Spice analyses.

    It's a lot of information to digest, but will try to free some time for it and see what I can lean from it.

    Concerning using arbitrary formulae in Spice, it is my understanding…
  • LDM

    Post
    Paradigmnoia

    A question for you,

    Have you any idea how much heat is leaking away through the wires which connect to the heating element.
    For Lugano we have some values, although I think the values should be somewhat lower (Something to address in a…
  • LDM

    Post
    Paradigmnoia


    The reflected radiation is equal to being directly radiated, I would think. I don't see how it is additive.

    Direct radiation from a surface to the background is proportional to the emissivity.
    Reflected radiation is proportional to (1…
  • LDM

    Post
    THHuxleynew

    In fact the Lugano authors take the smallest radius for area (10mm) when a better approximation to the area would be half way between smallest to largest radius. That gives +11.5% on the area, a factor of 1.115. The fin area, measured
  • LDM

    Post
    (Quote from THHuxleynew)


    Appreciating your comments and the discussion
    I have at least for two days not the time to digest the information you provided and to comment on it.
    But I will be back.


    Regards,

    LDM
  • LDM

    Post
    (Quote from Paradigmnoia)


    If you besides the view factor also incorporate the emissivity factor for reflected radiation, then I calculated a total factor 1.51.
    That would bring the diameter of the equivalent bare tube to about 30 mm.
    This factor 1.51 is…
  • LDM

    Post
    (Quote from Paradigmnoia)


    .0167/.0125 = 1.34

    For the fin height of 2.3 mm the "effective surface area " increases by a factor 1.34 compared to a bare tube.
    Thus the new effective surface area becomes 1,34 * 0.0125 = 0.0167 square meter
    For a bare tube…
  • LDM

    Post
    (Quote from THHuxleynew)


    Neither TC nor the Lugano authors used Fbg and therefore they were both also correct to use A not Afin.

    That they both used A and not Afin * Fbg is not a prove that they where correct.
    It can also mean they both where wrong and…
  • LDM

    Post
    (Quote from Paradigmnoia)


    You can buy them !
    See http://uk.farnell.com/multicom…-film-0r-0-25w/dp/9339027