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The thermal design of huge systems, huge in terms of number of components not their size, enforces the usage of dedicated SW packages in which each component needs to be modeled adequately. Detailed 3D modeling is not possible at early design phases. An adequate compact thermal model (i.e. one with very few degrees of freedom) of each component should be used instead. It must be cast in a form that makes it usable in SW packages, to model the behavior of each component regardless of surrounding objects. This fact has long been recognized for thermal conduction problems, which was solved using the so-called Boundary Condition Independent (BCI) models. For convection, the model universally admitted is that of the Heat Transfer Coefficient (HTC), which is obviously not BCI. It can always be used for small systems using a spread sheet that will have to be manually readapted for each new system topology. For large systems, automated BCI model generation is mandatory, which is the objective of this work. In this work, a new approach is proposed that generalizes achievements in building BCI compact models for thermal conduction to thermal convection. It offers many advantages over classical HTC models, including in particular its ability to handle conjugate heat transfer problems in a much more accurate, although a bit more involved, way. The level of complexity remains orders of magnitude less than full 3D analysis, which makes the proposed approach adapted for preliminary design phases.