[cysanghavi]

Hi,
I am running a CHT transient Simulation and trying to model the Radiation losses.
I include the Monte carlo Radiation model for modeling the Radiation losses.
I get a warning:
In Analysis 'Flow Analysis 1' - Domain Interface 'Default Fluid Solid Interface': At least one domain coupled to this interface is either a solid domain with radiation or has a laminar fluid flow with radiation. When such a domain is coupled by an interface with a Heat Transfer Interface Model, accuracy issues can arise with calculating the temperature of the wall.

What does it mean with accuracy issues. ?
I fail to understand. The Radiation model is for the solid Domain.
I have a laminar flow.

I include Radiation model aas below:

radiation_model.PNG.

[ghorrocks]

Please do not post multiple identical posts. If people are not answering your post think about why not - and improve your question. Do not just post the same thing all over again. I have removed the duplicate post.

Your problem is from something in how you set up your model. I cannot tell what from the simple information you have posted.

But before you consider that - do you really need the Monte Carlo radiation model? Would the Discrete Transfer model be adequate? In fact, would a heat sink on the surface of the body with the simple radiation heat transfer equation be enough? Then you don't need to model radiation at all.

[cysanghavi]

Sorry for duplication. I got a message yesterday, that I posted in the wrong Forum and my post is deleted. So I reposted.
I would be careful next time about this. Thanks for notifying this.

1. I want to model Radiation of a solid surface which is at a consireably high temp. (600K). See how it cools with time.
In solids I only have a Monte carlo Option for Radiation modeling.
The only other way I could think is using a CEL to model q = σ T4 -T04 A.

[ghorrocks]

Does the radiatitive heat pass through the solid? In other words, is the solid transparent (or at least partially transparent)? I am not referring to the conducted heat here, just the radiation.

Or does it just pass through the air and heat the surface of the solid?

[cysanghavi]

Ahhhhh... Now I get your point. Your question answers my question. !!
I am stupid.
My material is silicon carbide which is opaque. So I would probably not need a radiation model for the solid. I will check with the emissivity coefficient for silicon carbide.
For a radiative model heat loss in a fluid model, I think the losses are high since the temp is high in the range of 600K.
So I would use a discrete transfer model for heat losses for this model and check the model how it works.
I guess analytical calculations also work.

[ghorrocks]

The analytical calc will work fine providing surfaces do not irradiate other surfaces significantly. In the flutes of the drill (I assume it is a drill) this probably will happen so that means you will need the discrete transfer model.

Either way, this is a zillion times easier than with the Monte Carlo model.

[cysanghavi]

Perfect analysis!!

For my case, the flutes of the drill are not at conisderably high temperatures.
I guess I can neglect radation losses in this region.
Only the cutting edge of the drill is at a high temperature.
Thus it would be a good idea to analytically evaluate. or use discrete transfer model.

The problem is I cannot include radiative losses without creating a fluid domain of the surrounding air where it loses heat.
I can model convective losses to the surrounding air by HTc BC.

So I guess, Using a CEL expression to combine this convective and radiative losses will make more sense unless you know of some other way. !

[ghorrocks]

A CEl expression to combine convection and radiation is easy and works fine. If this is an appropriate boundary condition then I would use it.