Design and Characterization of Fluidic and Thermal Properties of 3D Woven Lattice Materials for Heat Exchange Applications

3D woven lattices;permeability;heat transfer;topology optimization;multi-functionality;Materials Science & Engineering

Zhao, LongyuHemker, Kevin J. ;

Johns Hopkins University

关键词: 3D woven lattices;    permeability;    heat transfer;    topology optimization;    multi-functionality;    Materials Science & Engineering;   

Others  :  https://jscholarship.library.jhu.edu/bitstream/handle/1774.2/44629/ZHAO-DISSERTATION-2016.pdf?sequence=1&isAllowed=y

瑞士|英语

来源: JOHNS HOPKINS DSpace Repository

【 摘 要 】

Architectured materials are being developed rapidly to meet the increased demand for multi-functionality. The innovative approach blends combinations of materials and the optimization of geometry with microstructural design to obtain materials with unusual combinations of properties. Recently, a novel lattice material that combines a 3D weaving technique with constrained topology optimization was designed and fabricated to maximize fluid permeability and shear stiffness. Due to the material’s high thermal conductivity, high specific surface area and torturous flow path, excellent thermal properties were observed as well. This thesis examines the design and characterization of the fluidic and thermal properties of the 3D woven materials for heat exchanger applications.Fluid permeability was optimized in one direction within the 3D weaves but it was characterized in all three orthogonal directions under laminar flow regime. Experimental results were compared to finite element modeling based on data about wire spacings in the fabricated weaves that was obtained using either optical microscope measurements or Xraytomography; the predictions and measurements agree quite well. The weaves showed significantly higher normalized permeabilities at different volume fraction of materials compared to other common porous media such as foams and trusses. The high permeability of the weaves validates the topology-optimized design.Three performance indices – pressure drop, average substrate temperature and substrate temperature uniformity – were then characterized on the weaves for heat exchange applications. Due to the weaves’ porosity in three dimensions, both axial (1D) and bifurcated (2D) flow patterns were examined and compared using water or air as coolant. The weaves were then compared to other common heat exchange media using dimensionless parameters such as friction factors, Nusselt numbers, and thermal efficiencies at different Reynolds numbers, under the axial flow pattern. Given that none of the flow patterns is superior for all three properties, we developed a novel flow manifold and combined it with the weaves to address these short comings.Following design the flow manifold was 3D printed and combined with sections of weaves to create a new weave/manifold system. The flow manifold has the distinct advantage of segregating a large area into many unit cells within which properties can be controlled and repeated. In addition, it can enable a flow pattern in 3D that allows uniform impingement of the coolant onto the heated substrate surface. The three performance indices noted above were quantified and compared to those for the open space/manifold system (with no weave) and the weave only system (with no manifold). The weave/manifold system demonstrates superior performance and highlights the benefits of combining a heat exchange media with a macroscopic flow guide. Lastly, further optimization can be performed to tailor the properties of the manifold and the 3D weaves for different applications.