Re: Natural Convection in a Vertical Column

Brent Cullimore <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...

> 
> So CFD might be valid, but still might not be worth the bother.
> 

I kind of had that suspicion. Although the geometry is relatively
simple the physics is messy.

> What is going on at the ends (top and bottom)? That will have a lot of
> influence on the flow field. If they're completely open, it is a
> chimney effect and you can work with 1D methods, which are quick to
> solve and allow you to test uncertainties.  Or perhaps there is a
> horizontal section of the conduit at either end?
> 

I have done some 1D calculations which I think model a "typical"
section fairly well. The problem is that this a closed column which is
approximately 40 ft. in length. As a result there is 40 ft. of power
cable generating heat that will naturally rise to the top of the
column. This invalidates some of the boundary conditions I'm using,
specifically the ambient air temperature surrounding the components.

The problem is further complicated by that fact that the air outside
the column is considerably cooler than that inside. This give rise to
more complicated phenomena such as recirculation and entrainment.

>
> Any test or empirical data at all? You can always calibrate a model to
> that, however sparse, to better trust any predictions of untested
> cases.
> 

Unfortunately not. This is an entirely new design. 

Thanks for the input.

Russ D.