Re: Natural Convection in a Vertical Column

If you are working on a fixed installation, the IEE wiring regulations may
well limit what you can do, ( U.K. only ).

Even if you are outside the U.K. they are a useful guide to what is safe,
and are extremely practical ( reading between the lines I smell frying
electrician.... :-) ).

They also contain a lot of tables giving information on common cable and
wire types.

--
Jonathan

Barnes's theorem; for every foolproof device
there is a fool greater than the proof.

To reply remove AT

"Russ" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> I am currently analyzing a problem involving a long vertical column
> with a relatively small conduit along the length column containing a
> group of power cables. There is a significant amount of heat
> generation in the cable due to a large current. I'm primarily
> interested in the temperature of the conductors and surrounding
> insulation.
>
> It is fairly straightforward to take a control volume and perform a
> simple conservation of energy calculation to obtain component
> temperatures. This assumes that the temperature of the surrounding air
> is determined exclusively by that of the components.
>
> In reality, since there is heat generation along the entire cable,
> natural convection will carry the heat upward and result in a higher
> air temperature at the top of the column. My problem is to quantify
> what "higher" is. I can do a parametric study to examine the component
> temperatures as the surrounding air temperature increases but I need
> some qualitative means of determining where we're really at along this
> parametric curve. The simplified analysis yields temperatures that are
> close to the specified limit for the insulation, even a modest
> increase in temperature could potentially push the insulation over the
> limit.
>
> I've been considering a CFD analysis of the entire system but I have
> some concerns about the viability of CFD for natural convection
> modeling.  Also, CFD modeling, even for this relatively simple
> geometry may be a massive undertaking. I have done some work in CFD
> for forced flow without any temperature considerations but I'm afraid
> that introducing this additional level of complexity will make CFD
> unreasonable for this application. Any thoughts on that?
>
> I'm looking for any suggestions or reference information that you may
> have. Although CFD is an option I'm considering I'd be interested in
> any potential analytical approach.
>
> Thank you,
> Russ D.