Thermal analysis of hybrid circuits with variable heat transfer coefficient

This paper, based on the practical example of a hybrid test circuit, illustrates the importance of proper modeling of the heat transfer coefficient dependence on surface temperature rise and fluid velocity in air cooled electronic systems. The presented experiments show that for the considered circuit the value of the heat transfer coefficient strongly depends on both these factors, thus its changes have to be taken into account in thermal simulations. A simple empirical relation proposed here by the authors allows accurate assessment of local heat transfer coefficient values in different cooling conditions and significant increase of thermal simulation accuracy.