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Microvascular Composites for Novel Thermal Management Devices


OBJECTIVE: To develop high-performance thermal management devices based on multifunctional design of microvascular composite materials and thereby to allow a precision control of the network passages tailored to specific cooling applications. DESCRIPTION: Compact, efficient heat exchangers enable improved operation of many thermal management devices such as Joule-Thomson (J-T) coolers. Most J-T heat exchangers are either metal finned-tube devices with limited surface area between the solid and gas streams, or etched-glass/silicon devices that allow relatively limited gas flow and cooling power. A micro-capillary array based heat exchanger offers the potential for both large surface area and large gas flow, with a manufacturing process that offers low-cost mass production. Within this context, novel microvascular composites recently developed offer precision control of the network passages tailored to specific cooling applications with textile weaving techniques allowing incorporation of high-performance structural fibers simultaneously. Underpinning this method is the efficient thermal depolymerization of catalyst-impregnated polylactide fibers with simultaneous evaporative removal of the resulting lactide monomer. The hollow channels produced are high-fidelity inverse replicas of the original fiber"s diameter and trajectory. This method has yielded microvascular fiber-reinforced composites with channels over one meter in length that can be subsequently filled with a variety of liquids and gases. PHASE I: Demonstrate the scaled-up fabrication of microvascular composites with the mechanized weaving of sacrificial fibers into 3D woven glass fiber performs and subsequent vaporization of sacrificial components. Establish new design concepts of varying the position, length, diameter, and curvature of fibers forming microchannels. PHASE II: Develop multifunctional structures of microvascular composites with 200-500 micron diameter parallel channels nested in close proximity to produce a counter-flow heat exchanger. Demonstrate how to circulate the microvascular network with a fluid having the desired physical properties. Assess whether the performance of the J-T heat exchanger made of microvascular composites can be enhanced by incorporating carbon fibers of highly anisotropic thermal conductivity. PHASE III: Applications include IR sensors for target tracking for use in both commercial and military aircraft. Evaluate the cooling performance of prototypes under mechanical stress and introduce remedies to avoid undesirable malfunctioning. Conduct manufacturing and testing program to ensure service life. REFERENCES: 1. A. P. Esser-Kahn, P. R. Thakre, H. Dong, J. F. Patrick, V. K. Vlasko-Vlasov, N. R. Sottos, J. S. Moore, S. R. White. Three-Dimensional Microvascular Fiber-Reinforced Composites, Advanced Materials 23:3654-3658 (2011). 2. Y. Fan, H. Nishida, T. Mori, Y. Shirai, T. Endo. Thermal Degradation of Poly(lactide): Effect of Alkali Earth Metal Oxides for Selective L,L-Lactide Formation. Polymer 45(4):1197-1205 (2004). 3. V. Natrajan, K. Christensen. Non-intrusive Measurements of Convective Heat Transfer in Smooth- and Rough-Wall Microchannels. Part I: Laminar Flow. Experiments in Fluids, 49 (5):1021-1037 (2010).
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