Macro-Based Heat Exchanger Model Limitations
The macro-based heat exchanger model is in v6.1. There are some limitations that one need to be aware of.
1. The macro-based approach to modeling heat exchangers, if used on pure tet mesh, is known to result in less accurate results. The solution process is also not very stable. It is recommended to use either hex mesh or wedges such that the macros are aligned with the grid lines.
For modeling radiator in underhood, we recommend using wedge elements. The inlet and outlet faces of the radiator will have triangular faces. How to align grid lines when using wedge elements is demonstrated in a tutorial that is created. Please contact firstname.lastname@example.org to get that tutorial.
When using hex mesh in the core, make sure you use uniform mesh.
2. Make sure you use uniform mesh distribution so that all macros have the same number of elements.
3. For more accurate solution we also recommend to use the same number of macro discretization as the mesh discretization in Width (Pass-to-Pass direction - Number of Col./Pass) and Height (coolant direction - Number of Raws/Pass). For example, if number of cells in the coolant flow direction is 50, use 50 for "Number of Raws/Pass".
4. Also, for better results, number of cells in the Width direction (pass-to-pass direction) should be divisible by "Number of Passes" used.
All the above requirements, if followed, will lead to better result and more stable solution process. It will lead to all macros to be the same size.