Dissertation Defense: Jerald Armen

Abstract: With advances in micromachinery, the acceptance of disaggregation of sensors, and easy-to-use microcontroller platforms on satellites, the size of mission structures are getting dramatically smaller and faster, this results in greater localized heat generation, requiring more reliable thermal management systems. The emergence of advanced additive manufacturing (AM), such as selective laser sintering (SLS) and engineering materials, such as low-melting eutectic liquid metal (LM) alloys and synthetics ceramics offer new opportunities for thermal cooling systems. Therefore, there has been an opportunity for adapting in-situ AM to overcome limitations of traditional manufacturing in thermal application, where improvements can be achieved through reducing thermal contract resistance of multi-layer interfaces. In this regard, this work investigates adapting in-situ AM technologies to embed prefabricated components, such as ceramic tubes, inside of metals without parting surface, resulting in more intimate contact between the metal and ceramic. A focus was placed on using more ubiquitous powder bed AM technologies, where it was determined that the morphology of the prefabricated LM compatible ceramic tubes had to be optimized to prevent collision with the apparatus of powder bed based AM. Furthermore, to enhance the wettability of the ceramic tubes during laser fusion, the surfaces were electroplated, resulting in a 1.72X improvement in heat transfer compared to cold plates packaged by conventional assembly. Additionally, multiple AM technologies synergistically complement with cross platform tools such as magnetohydrodynamic (MHD) to solve the corrosion problem in the use of low melting eutectic alloy in geometrically complex patterns as an active cooling system with no moving parts. The MHD pumping system was designed using FEA and CFD simulations to approximate Maxwell and Navier-Stokes equations, were then validated using experiments with model heat exchanger to determine the tradeoff in performance with conventional pumping systems. The MHD cooling prototype was shown to reach volumetric flow rates of up to 650 mm³/sec and generated flow pressure due to Lorentz forces of up to 230 Pa, resulting in heat transfer improvement relative to passive prototype of 1.054.