Experimental characterization of a self-adaptive shape memory alloy cooling approach to regulate temperature under varying heat loads

Abstract

Electronic cooling devices typically aim to provide low thermal resistance, however, for many applications, temperature non-uniformity across the cooled object is also a key parameter, as it impacts reliability. Tailored microchannels or fin layouts are examples of cooling devices that can be designed to reach uniform wall temperatures but require known and constant heat load distributions. In this work, a self-adaptive liquid cooling device is proposed to provide constant and uniform temperature distributions under spatially and time dependent heat load scenarios. The working principle is based on the use of the Two-Way Shape Memory Effect (TWSME) of trained shape memory alloy (SMA) wings that elevate into the flow to reduce the convective thermal resistance when a critical temperature is reached. The conditions for proper operation are first defined analytically. Then, the impact of SMA wings on thermal resistance is experimentally investigated. Finally, the ability of the self-adaptive concept to maintain a constant wall temperature when the heat flux increases, is demonstrated. In the studied case, for fixed inlet coolant temperature and flow rate, the liquid cooling device was able to maintain the temperature of the cooled object within an interval of 7 °C for a heat flux varying from 32.8 to 67 W/cm2. Without self-adaptation, a temperature variation over 85 °C was expected for the same cooling device, corresponding to an order of magnitude improvement.