Meshing for Monte Carlo Radiation

Zoran

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Dear experts, I do my first radiation simulation with Monte Carlo in a rectangular channel consisting of different parts & materials (e.g. ZnSe window, metal and ceramic walls, ...). The goal is to find out the radiation from the adjacent channel walls to a specified wall surface area (target plate). Air within this channel is treated as transparent medium and since convection is not considered (in a first approach) only the solid is modeled & meshed, i.e. there is no fluid domain. I've done some test runs with different parameters (emissivity, temperature BC, # of histories) to see what happens. In CFX-Post I visualize the "Wall Irradiation Flux".

Here are my questions:

1) Is it possible to define a domain (window) as a transparent solid? With Monte Carlo (Surface to Surface) only opaque solids are supported. Boundary Details > Thermal Radiation > Option: ... I used to model the ZnSe window (transmittance >90%) as a opening... Any suggestions how to overcome this problem? In the help manual "Radiation Properties" it is described that transparent media has an absorption coefficient and scattering coefficient of zero.

2) Is a (fine) mesh necessary at all or just a (1part-1element) mesh converted directly from the raw blocking? With this I would like to know whether the generic rays/photons in MC are dependent on the nodes or created by random within the mesh-element. The fact that there is a "coarsening control" tells me that the number of elements is relevant but I'm not sure...

3) Is the # of histories defined per domain-mesh-element or just per domain? Here I guess it is per domain but then in question 2) the number of mesh elements in a domain is not important for pure radiation modeling. I've defined a domain for each part of the channel.

I hope someone can give me an advise. Thanks in advance!

Zoran