Numerical evaluation of bimetallic self-adaptive fins acting as flow disturbing elements inside a microchannel

The continuous increase in power density of integrated circuits (IC) due to the ever-increasing rate of data and communications and the constant push for size and costs reduction, is settling thermal management as one of the major concerns for the ICT industry. Current cooling solutions focus on high compactness and low thermal resistance. Nevertheless, several electronic applications, such as multicore processors or 3D-IC, present non-uniform and time-dependent heat load scenarios, what leads current systems to both oversized pumping powers for changing conditions and optimized temperature uniformities of the chip only for a given heat load distribution. To overcome these problems, this work proposes a system based on self-adaptive fins acting as passive thermal actuators, where the fins will be activated, without any external excitation, in function of their own temperature due to the principle of thermal expansion of the materials. The self-adaptive fins are based on bimetals that act as flow disturbing elements inside microchannels only for high cooling demands, otherwise, the fins remain in a flat position to reduce the pressure drop of the cooling device. Consequently, the system is able to tailor its internal geometry to time dependent and non-uniform heat flux distributions, optimizing the local heat transfer enhancement and the pressure drop to the instantaneous cooling needs. The impact of this cooling solution within a microchannel has been numerically evaluated in this work, as well as different structural parameters of the bimetallic fins to ensure the self-adaptive behavior. Results showed a 40% heat transfer enhancement and a pumping power reduction up to 34% compared with a system of fixed vortex generators.