Hello..... iam in search of tutorials related to structural thermal analysis. how to link the structural problems with the thermal......

i am doing a project using cfx... i am finding the air flow distribution in a wind box assembly of a corner fired boiler. while modelling, should i have to model the flow path as solid or as a hollow as in the drawing.And if i had to make it a solid protrusion...how will i do it.... because it is a complicated model....is there any option to subtract the flow path from the original model...please do reply....