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Öztekin
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 Posted: Mon Oct 20, 2003 9:35 pm Post subject: Forced convection in a sphere |
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Hi,
Does anyone know about forced convection in a spherical container
which has an inlet at bottom and an exit at top? I need all knowledge
about it.
Thanks... |
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Mike Halloran
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| Posted: Tue Oct 21, 2003 8:34 am Post subject: Re: Forced convection in a sphere |
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Forced convection means you use fan(s) and baffles to make the air go where you
want it to go. What else do you need to know?
-Mike- |
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?ztekin
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| Posted: Tue Oct 21, 2003 10:22 pm Post subject: Re: Forced convection in a sphere |
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I mean a spherical container that has a heater at outer surface and, a
water inlet at bottom and outlet at top. A water flow will occur in
it. I would like to examine what will occur in this container
(temperature distribution, convection mechanism, Nusselt numbers,
etc.). I want to make a study on it. I think that It may be a base for
further studies.
Analytical calculations may be difficult because of turbulent flow.
But, If I prepare a system and measure temperature distribution in it,
what can I make ? Do you know studies like this. Do you suggest me
anything? |
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Mike Halloran
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| Posted: Wed Oct 22, 2003 7:13 am Post subject: Re: Forced convection in a sphere |
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Using a sphere greatly complicates the mathematics, and the fabrication of
experimental apparatus, and the difficulty and expense of heating the surface
uniformly or at all, and the difficulty of observing and measuring what is
happening inside.
Whether the container is spherical or not, you will soon discover that the flow
fields at the ends are not symmetrical. The water entering the container will
tend to stay in a coherent stream (without a vena contracta; that only happens
in air), and will entrain water from the container, inducing a generally
toroidal flow, downward at the container wall. The isobars in the stream will
be roughly parabolic.
At the exit end of the container, the isobars will be hemispherical, and the
flow will be radially inward from all directions, not concentrated along the
outlet bore axis.
[If you think about it, that asymmetry in isobars and flow fields around
apertures, depending on whether the flow is in or out, is why we don>t
suffocate on our own exhalations, so it>s a good thing. It just makes modeling
more difficult.]
In between the flow will be generally toroidal. Which might qualify as 'not
irrotational'. Which might make the math even worse. It makes my head hurt.
The apparatus you describe will provide you decades of questions to ask, and
frustration, but I doubt you>ll be able to extract much useful knowledge from
it. Find a simpler problem unless you want to make a career of it.
-Mike- |
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