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 Aleksander May 8, 2009 14:38

Hi all!

I am trying to do a cfd model of a panel radiator. The geometry is a vertical parallel plate array, heat transfer mediums are air and oil (for example see http://www.howard-ind.com/HowardTran...elRadiator.jpg, mind that coating in my case in zink).

Here is my question:

Heat transfer from the radiator is influenced by the horizontal center (where the oil pipe is) distance between radiators (see http://www.warm.it/images/Catalogo1202d.pdf for functional dependence).

Does anyone know what is the reason for such high influence (functional extrapolation to separation distance of 520mm - panel width, yields 83% of emisson when radiator centers are 750mm apart?)? Also, what do you think about the radiation contribution when the reflective coating is used (i think that in the case of reflective coating, effective radiation surface would be the entire surface of the radiator, even between the panels)?

Lets discuss :)

This type may be better known as column type radiator

 Aleksander May 9, 2009 06:22

Ok, i have tested the sst transitional k-w model in fluent. 3D model, 1.2m cells with horizontal central distance of 750mm yields 171W/m2 while 2d soulution gives 141 W/m2, thats 82% (1.6m vertical parallel plates 333.15K isothermal). Pretty close, now i have to test the influence of the turbulent intensity and hydraulic diameter on the vertical open boundary between radiators. Testing laminar model in 2d gives 141 W/m2 while 3d model (same settings as 3d sst transitional k-w) gives 140 W/m2. Let's continue testing...

 Ahmed May 9, 2009 14:41

It depends on what exactly are the objectives of your analysis.
If you really want to understand what is taking place there, and be able to answer all kinds of questions that might come to your mind, I would put CFD aside and start developing a mathematical model for that heat exchanger. The procedure is straight forward though it will lead to a coupled set of partial differential equations, in the simplest case it will lead
to an ugly mathematical expression obtained by a Laplace Transformation technique but it can answer any raised questions.
Check the literature on Heat Exchangers Performance and the works by Vedat Arpaci
Cheers and enjoy your math journey.:confused::confused::confused:

 Aleksander May 9, 2009 15:31

I only need heat transfer coefficient and emission dependence of oil flow speed on heat transfer, but i have not found any literature on this topic yet. Using parallel plates heat transfer coefficient clearly does not work, as the flow is turbulent on the edges. The air speed is around 0.9m/s in 2d geometry, so i fall in transitional or turbulent range (plates are 0.035m apart)...

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