The most efficient method avoids trying to resolve the pipe wall thickness with the mesh. 1. Create and mesh 2 fluid domains for the regions inside and outside the piping – with full contact between the two. The mesh does not have to be 1:1 at the contact, but the mesh sides should have roughly the same mesh resolution 2. In CFX Pre, create a fluid-fluid domain interface to connect the two domains 3. Under the Additional Models tab panel, set the Mass and Momentum option to No Slip Wall, set the Heat Transfer option to Conservative Interface Flux, and use the Thin Material option when providing the wall material and thickness 4. Both fluid domains will see the interface as a thin wall. A 1D conduction assumption is used to model heat transfer through the wall (no in-plane conduction) using the thickness provided. The thermal conductivity and specific heat capacity is picked up from the material properties of the specified material