Fluid Flow with Radiative and Convective Heat Transfer for Temp and Velocity Cal

[taylorrbenson]

I am a beginner trying to use ANSYS fluent to model a problem that includes radiative heat transfer and convective heat transfer. There are three concentric cylinders. There is a constant temperature profile on the inside of the inner cylinder. The first cylinder will radiate heat from the outer walls to the second cylinder assuming a vacuum will be pulled so that no convection or conduction through air occurs in that space. Between the second cylinder and third cylinder, there is air flow that allows for convection from the walls to the air and radiation between the two cylinder walls. At the point that I am in Ansys Fluent, I need it to calculate the temperature profiles along the z-axis moving along all the cylinders from bottom to top, using that temperature to calculate the temperature of the air which in turn will determine velocity based on buoyancy force and heat transfer coefficient at each node moving up the wall of the cylinder. These values will then be used to continue to calculate at each node as we move up the wall. I have created a geometry and mesh. Once in Fluent I need have turned radiation on from surface to surface. It will only allow me to click the walls from the cylinders in which a vacuum is pulled in between them which may be an issue arising from the fact that interfaces between the air and walls formed for the space between the two outer cylinders. That is the first problem. To model radiation, I assume I turn on surface to surface and put them in participating boundary zones while the non participating are in the other zone. Then I go into the wall and edit those by inputting my emissivity value. Now from here I can not figure out how to add convection as a heat transfer mechanism to the air and have it calculate the values mentioned previously that need to be calculated. Attached is an image of the Fluent model currently.

[Rob]

Try and avoid non conformal boundaries (interfaces) on walls as it'll make the set up more complex. Convection is a flow effect, so Fluent will handle that without much help. Radiation needs more careful consideration, so I'd advise doing the tutorials (Help in Fluent) and any/all of the heat transfer courses in Learning>Fluids. 

Note, vacuum isn't available in Fluent as it's a continuum based solver. S2S can't handle absorbtion so you may want to look at DO/MC too.