A multi-grid based multi-scale thermal analysis approach for combined mixed convection, conduction, and radiation due to discrete heating

A multi-grid embedded multi-scale approach is presented for conjugate heat transfer analysis of systems with a wide range of length scales of interest. The multi-scale analysis involves a sequential two-step "zoom-in" approach to resolve both the large length scales associated with the system enclosure, and the smaller length scales associated with fine spatial structures of discrete heat sources contained within. With this approach, computation time is shortened significantly, compared to conventional single-step computational fluid dynamics/computational heat transfer (CFD/CHT) modeling, with a very fine mesh. Performance of the two-step multi-scale approach is further enhanced by integrating the multi-grid technique in the CFD/CHT solver Implementation of the enhanced approach is demonstrated for thermal analysis of an array of substrate mounted discrete heat sources cooled by mixed and forced convection, with accompanying experiments performed for validation and for the assessment of the importance of mixed convection. It is found that the multi-grid embedded multi-scale thermal analysis reduces simulation run time by 90% compared to the multi-grid integrated single step solution. The computed temperatures were in good agreement with measurements, with maximum deviation of 8%.