Abstract:As the applications for additive manufacturing have continued to grow, so too has the range of available materials, with more functional or better performing materials constantly under development. This work characterizes a copper-filled polyamide 6 (PA6) thermoplastic composite designed to enhance the thermal conductivity of fused filament fabrication (FFF) parts, especially for heat transfer applications. The composite was mixed and extruded into filament using twin screw extrusion. Because the fiber orientation within the material governs the thermal conductivity of the material, the orientation was measured in the filament, through the nozzle, and in printed parts using micro-computed tomography. The thermal conductivity of the material was measured and achieved 4.95, 2.38, and 0.75 W/(m·K) at 70 • C in the inflow, crossflow, and thickness directions, respectively. The implications of this anisotropy are discussed using the example of an airto-water crossflow heat exchanger. The lower conductivity in the crossflow direction reduces thermal performance due to the orientation in thin-walled parts.
This work describes the use of deposition-based additive manufacturing (AM) techniques to fabricate air-cooled, two-fluid heat exchangers. The project focused on a Heating, Ventilation and Air Conditioning (HVAC) application and used an industry standard copper/aluminum heat exchanger manufactured with conventional technology as the basis for assessing the performance. The manufacturing constraints associated with using deposition-based AM technology for this application include the need for a continuous tool path within each build layer that allows uninterrupted extrusion and therefore defect free water channels that correspond to a reliably leak-tight heat exchanger. A geometry that respects these constraints was developed, simulated, optimized and finally manufactured and tested. The measured performance match the predicted performance and the test coupons exhibit performance that approaches and in some cases exceeds conventional technology.
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