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 Carlos Ortiz July 23, 2002 20:08

Convection problem

Hello there,

I'm trying to solve a natural convection problem inside a metal enclosure, where air is contained as well as heat sources corresponding to the primary and secondary winding and the magnetic core in a dry type power transformer.

On the outside of the metal casing I declare natural convection with a relevant heat transfer coefficent h and a free stream temperature.

I consider the fluid as ideal gaz for the density computation. As for the rest I declare physical properties at average working temperature 60 deg. C. The measured temperature distribution oscillates between 29 and 99 deg C. So I initialize the velocity at zero, the temperature at 65 deg. C and the gauge pressure at +8000 inside the metal enclosure.( This is a guessed value). I declare a working pressure of some kPa above ambient pressure and a working temperature of 65 deg. C.

This kind of problems are normally solved by considering a temperature gradient, between two regions of interest. In my case I want to deduce tempeature distribution in solids by the action of fluid circualtion by body forces. For pressure I use Presto, SimpleC and second degree upwind for the rest. My underelaxation coefficients are all set at 0.8, is the only way I can get the residual for continuity to move.

I do not get proper solution, there is too much oscillation in the continuity residual and the pressure computation does not move at all, any suggestions?

Carlos Ortiz Universite du Quebec a Trois Rivieres Canada

 Sridhar July 24, 2002 11:31

Re: Convection problem

I think for Pressure you need to use Body forced weighed option instead of Presto. May be this helps.

Sridhar.

 Carlos Ortiz July 24, 2002 14:42

Re: Convection problem

Hi Sridhar,

Body Force weighted helped in deed, I also used power law for energy and momentum. There is a big change in the computation but I still do not get convergence.

Thanks a lot for your message.

Carlos

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