Learning Forum

[Jason Potticary]

I'm a complete beginner interested in modelling total heat loss from inside a sphere by varying the thermal conductivity of an internal insualting layer. I've bulit a 'gobstopper' model with 4 spheres nested inside each other giving me a 50 cm diammeter sphere thermal body, surrounded by a 5 m diammeter air sphere, surrounded by a 5.1 m diammeter insulating sphere surrounded by a 5.2 m diammeter housing sphere. All of this is inside a cube of air with side length 10 m.

My plan is to set the thermal body to, say 30 C and the cube of air to 5 C and see how, by varying the termal conductivity of the outer two spheres, my total heat loss to the cube changes.

I have read some of the fluent tutorials and have a basic understanding of how to build the simulation, I'm just not sure how to organise read any of the output (residuals / monitors etc.) Is there a tutorial or webpage that could help me get my head in the right place with them that I could be pointed at?

Thanks.

[peteroznewman]

Jason, search for tutorials on Natural Convection. The density of air will change with temperature. Gravity will pull the heavier cold air down which will displace the lighter warm air up and create flow patterns in the air. The air flow will convect heat away from the warm sphere much faster than conduction, because air is a good insulator when it cannot move.

[Jason Potticary]

Sorry, I should have been more specific. I meant specifically how to learn about assigning surfaces and materials to parts of the mesh and how to set up the monitors to give me something I can use and read at the end. I've built the spheres to be solids and fluids but am not really sure how to assign them to materials and what fluent parameters to use when setting up the calculation.