[ekha]

Hi,

I am trying to a 3-D case to model a transient laminar heat transfer and compare the results with experimental one. In my case, the bottom layer is subjected to constant heat flux 1000W (temperature at 3000K) while the side wall are insulated and the top is free surface.

the experimental setup as follows:

The tank is made of double glass sidewalls with 6mm air gap to ensure thermal insulation. The bottom of the tank is made of black anodized aluminium, the under side of the base is insulated with a source of heat of 1000-W halogen lamp (colour temperature of 3000 K).

My questions are:

What type of thermal boundary condition I need to set up for the insulated walls? does mixed BC works in this case or I need to define a new material for the side walls with insulation properties?

For the bottom layer I have tried either to apply constant heat flux or constant temp (not combined as in the user guide) and simulate for 200 timesteps (10 sec) but I didn't get plumes at the bottom layer, Do I need to use a S2S radiation in this case? what are the best options to apply similar source of heat at the bottom?

any help would be appreciated.



Thanks

[MKuhn]

If the air in the gap is moving (convection effects) then you have to model this. This could be the case, if the box is on the bottom hotter than on the top. If not than just define a three layer wall thickness, glass - air - glass and choose convection or mixed BC when you will also consider the radiation between your tank and the surroundings. For each layer you have to define a new material, ever for the air a "pseudo air-solid". Mixed BC has nothing to do with an insulation layer. Is just the combination of convection and radiation.
-- Moritz