A. James Clark School of Engineering
Permanent URI for this communityhttp://hdl.handle.net/1903/1654
The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item Development of Multi-Scale, Multi-Physics, Analysis Capability and its Application to Novel Heat Exchanger Design and Optimizaiton(2009) Abdelaziz, Omar A.; Radermacher, Reinhard; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Heat exchanger development using enhanced heat transfer surface designs and optimization techniques is a continuing effort that is constrained by current state of the art technology. Assessment of novel geometries and concepts are currently limited to experimental and numerical investigations on discrete levels. This dissertation aims at the advancement of the heat exchanger technology through the development of multi-scale multi-physics simulation tools for conventional and novel heat exchanger designs. A unified heat exchanger design and optimization framework was developed. This framework integrates the multi-scale multi-physics simulation capabilities with previously developed approximation assisted optimization techniques. The optimized designs are then interpreted in order to provide design guidelines for next generation air-to-water heat exchangers. These capabilities required the development of: (a) generic ε − NTU solver capable of analyzing the performance under geometrical variability, (b) systematic integration approach for CFD simulation at the segment level with the ε − NTU solver at the heat exchanger level, (c) refrigerant distribution analysis tool. The developed simulation tools were verified numerically using systematic techniques adopted from literature and validated experimentally using measured data from a prototype heat exchanger. The structural integrity under conventional operating pressures of the novel heat exchanger design was analyzed using FEM for different tube materials and different wall thicknesses. Finally, existing single phase water flow in microtubes correlations were investigated numerically. The best matching correlation was selected for incorporation within the multi-scale simulation tool. The approach described in this dissertation for the design and optimization of novel and conventional heat exchanger designs resulted in significant improvements over the current state of the art. Example performance improvements achieved in this dissertation show potential for 84 percent material savings and 61 percent volume savings for the same airside and refrigerant side pressure drop. The experimental investigations were in good agreement with the simulation results and demonstrated the superior performance of the novel design.Item PROPOSED BUILD GUIDELINES FOR USE IN FUSED DEPOSITION MODELING TO REDUCE BUILD TIME AND MATERIAL VOLUME(2009) Teitelbaum, Gregory Allen; Schmidt, Linda C; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The emergence of Fused Deposition Modeling as a small volume manufacturing process and a lack of explicit rules for improving the efficiency of this process bring necessity to the development of build guidelines. This work develops a proposed set of build guidelines for use in Fused Deposition Modeling (FDM). The guidelines are verified by the literature and experience, and validated by statistical analysis of quantitative FDM build data and qualitative review of example cases from student projects. The experimental data are obtained using the fabrication protocol for a Dimension SST Fused Deposition Modeling machine. Using simulation software known as CatalystTM, build time and material volume characteristics of many components of varying size and complexity were calculated. Eventually, this area of research should result in a robust set of rules that can fundamentally reduce the costs associated with FDM and can assist its ascent as a feasible full-scale manufacturing process.