Abstract
Enhanced Heat Transfer Performance by Shape Optimization of a Non-axisymmetric Droplet Evaporating on a Heated Micropillar
By
Haotian Wu
Department of Mechanical Engineering and Materials Science
Washington University in St. Louis, 2019
Research Advisor: Professor Damena Agonafer
The stacked multilayer 3D IC structure used in next generation high-powered electronics poses great challenges in dissipating their large heat flux, which causes extreme difficulties for traditional cooling technologies. In response, more advanced two-phase liquid cooling technologies, such as droplet evaporation, which utilizes the latent heat of vaporization to remove excessive heat, have been widely investigated. Compared to traditional single-phase cooling techniques, two-phase cooling based on droplet evaporation offers both high efficiency and an exceptionally high heat dissipation rate. Compared to a spherical droplet, a non-spherical droplet on a non-axisymmetric pillar, with its different perimeter-to-area ratio and meniscus curvature, exhibits very different interfacial mass transport features. In particular, the higher ratio of the perimeter length to the solid-liquid area provides a relatively larger thin film region and therefore a smaller thermal resistance, while the high local curvature facilitates a stronger local vapor diffusion rate. However, the optimal pillar shape is still uncertain. In this study, using the Particle Swarm Optimization algorithm, we develop a shape optimization tool for max non-axisymmetric droplet evaporation on a micropillar structure. The optimization tool integrates the algorithm calculation and curve generation in Matlab, the droplet shape generation in Surface Evolver, the geometry evolution in Solidworks, and the evaporation simulation in COMSOL. The optimized micropillar shape shows a 9% improvement in the heat transfer coefficient for the same liquid-vapor interfacial area and the same substrate area. Comparative evaporation experiments using fabricated micropillar samples with a baseline triangular pillar shape, validate the simulation results, with a relative error of less than 9.7% in evaporation rate.
","abstract_html":"<p>Abstract</p> <p>Enhanced Heat Transfer Performance by Shape Optimization of a Non-axisymmetric Droplet Evaporating on a Heated Micropillar</p> <p>By</p> <p>Haotian Wu</p> <p>Department of Mechanical Engineering and Materials Science</p> <p>Washington University in St. Louis, 2019</p> <p>Research Advisor: Professor Damena Agonafer</p> <p>The stacked multilayer 3D IC structure used in next generation high-powered electronics poses great challenges in dissipating their large heat flux, which causes extreme difficulties for traditional cooling technologies. In response, more advanced two-phase liquid cooling technologies, such as droplet evaporation, which utilizes the latent heat of vaporization to remove excessive heat, have been widely investigated. Compared to traditional single-phase cooling techniques, two-phase cooling based on droplet evaporation offers both high efficiency and an exceptionally high heat dissipation rate. Compared to a spherical droplet, a non-spherical droplet on a non-axisymmetric pillar, with its different perimeter-to-area ratio and meniscus curvature, exhibits very different interfacial mass transport features. In particular, the higher ratio of the perimeter length to the solid-liquid area provides a relatively larger thin film region and therefore a smaller thermal resistance, while the high local curvature facilitates a stronger local vapor diffusion rate. However, the optimal pillar shape is still uncertain. In this study, using the Particle Swarm Optimization algorithm, we develop a shape optimization tool for max non-axisymmetric droplet evaporation on a micropillar structure. The optimization tool integrates the algorithm calculation and curve generation in Matlab, the droplet shape generation in Surface Evolver, the geometry evolution in Solidworks, and the evaporation simulation in COMSOL. The optimized micropillar shape shows a 9% improvement in the heat transfer coefficient for the same liquid-vapor interfacial area and the same substrate area. Comparative evaporation experiments using fabricated micropillar samples with a baseline triangular pillar shape, validate the simulation results, with a relative error of less than 9.7% in evaporation rate.</p>","abstract_has_math":false,"creators":["Wu, Haotian"],"institution":null,"degree_name":"Master of Science (MS)","degree_level":"Thesis","degree_discipline":"Mechanical Engineering & Materials Science","degree_department":null,"school":null,"contributors":["Damena Agonafer","Damena Agonafer David Peters Ramesh Agarwal"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2019,"date_issued":"2019-12-14T08:00:00Z","date_published":"2019-12-14T08:00:00Z","updated_at":"2026-07-24T06:13:05Z","subjects":["two-phase liquid cooling","micropillar","perimeter-to-area ratio","Particle Swarm Optimization algorithm","evaporation simulation","heat transfer coefficient","Computer-Aided Engineering and Design","Engineering","Heat Transfer, Combustion","Manufacturing"],"languages":["English (en)"],"rights":["I have not registered my thesis with the U.S. Copyright Office, but intend to later."],"rights_urls":[],"identifier_entries":[{"key":"dc:identifier","label":"Identifier","values":["https://openscholarship.wustl.edu/eng_etds/486"],"render_values":[{"text":"https://openscholarship.wustl.edu/eng_etds/486","href":"https://openscholarship.wustl.edu/eng_etds/486","code":true}]}]},"links":{"outbound_url":"https://doi.org/10.7936/vfhm-j984","outbound_label":"DOI","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Damena Agonafer","Damena Agonafer David Peters Ramesh Agarwal"]},{"key":"dc:creator","label":"Author","values":["Wu, Haotian"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.available","label":"Dc Date Available","values":["2021-12-17T08:00:00Z"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Mechanical Engineering & Materials Science","McKelvey School of Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["Master of Science (MS)"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["two-phase liquid cooling","micropillar","perimeter-to-area ratio","Particle Swarm Optimization algorithm","evaporation simulation","heat transfer coefficient","Computer-Aided Engineering and Design","Engineering","Heat Transfer, Combustion","Manufacturing"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["English (en)"]},{"key":"dc:rights","label":"Dc Rights","values":["I have not registered my thesis with the U.S. Copyright Office, but intend to later."]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://doi.org/10.7936/vfhm-j984","https://openscholarship.wustl.edu/eng_etds/486"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Permanent URL: https://doi.org/10.7936/vfhm-j984"]},{"key":"dc:description.abstract","label":"Abstract","values":["Abstract
Enhanced Heat Transfer Performance by Shape Optimization of a Non-axisymmetric Droplet Evaporating on a Heated Micropillar
By
Haotian Wu
Department of Mechanical Engineering and Materials Science
Washington University in St. Louis, 2019
Research Advisor: Professor Damena Agonafer
The stacked multilayer 3D IC structure used in next generation high-powered electronics poses great challenges in dissipating their large heat flux, which causes extreme difficulties for traditional cooling technologies. In response, more advanced two-phase liquid cooling technologies, such as droplet evaporation, which utilizes the latent heat of vaporization to remove excessive heat, have been widely investigated. Compared to traditional single-phase cooling techniques, two-phase cooling based on droplet evaporation offers both high efficiency and an exceptionally high heat dissipation rate. Compared to a spherical droplet, a non-spherical droplet on a non-axisymmetric pillar, with its different perimeter-to-area ratio and meniscus curvature, exhibits very different interfacial mass transport features. In particular, the higher ratio of the perimeter length to the solid-liquid area provides a relatively larger thin film region and therefore a smaller thermal resistance, while the high local curvature facilitates a stronger local vapor diffusion rate. However, the optimal pillar shape is still uncertain. In this study, using the Particle Swarm Optimization algorithm, we develop a shape optimization tool for max non-axisymmetric droplet evaporation on a micropillar structure. The optimization tool integrates the algorithm calculation and curve generation in Matlab, the droplet shape generation in Surface Evolver, the geometry evolution in Solidworks, and the evaporation simulation in COMSOL. The optimized micropillar shape shows a 9% improvement in the heat transfer coefficient for the same liquid-vapor interfacial area and the same substrate area. Comparative evaporation experiments using fabricated micropillar samples with a baseline triangular pillar shape, validate the simulation results, with a relative error of less than 9.7% in evaporation rate.
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Enhanced Heat Transfer Performance by Shape Optimization of a Non-axisymmetric Droplet Evaporating on a Heated Micropillar
By
Haotian Wu
Department of Mechanical Engineering and Materials Science
Washington University in St. Louis, 2019
Research Advisor: Professor Damena Agonafer
The stacked multilayer 3D IC structure used in next generation high-powered electronics poses great challenges in dissipating their large heat flux, which causes extreme difficulties for traditional cooling technologies. In response, more advanced two-phase liquid cooling technologies, such as droplet evaporation, which utilizes the latent heat of vaporization to remove excessive heat, have been widely investigated. Compared to traditional single-phase cooling techniques, two-phase cooling based on droplet evaporation offers both high efficiency and an exceptionally high heat dissipation rate. Compared to a spherical droplet, a non-spherical droplet on a non-axisymmetric pillar, with its different perimeter-to-area ratio and meniscus curvature, exhibits very different interfacial mass transport features. In particular, the higher ratio of the perimeter length to the solid-liquid area provides a relatively larger thin film region and therefore a smaller thermal resistance, while the high local curvature facilitates a stronger local vapor diffusion rate. However, the optimal pillar shape is still uncertain. In this study, using the Particle Swarm Optimization algorithm, we develop a shape optimization tool for max non-axisymmetric droplet evaporation on a micropillar structure. The optimization tool integrates the algorithm calculation and curve generation in Matlab, the droplet shape generation in Surface Evolver, the geometry evolution in Solidworks, and the evaporation simulation in COMSOL. The optimized micropillar shape shows a 9% improvement in the heat transfer coefficient for the same liquid-vapor interfacial area and the same substrate area. Comparative evaporation experiments using fabricated micropillar samples with a baseline triangular pillar shape, validate the simulation results, with a relative error of less than 9.7% in evaporation rate.
"],"dc:identifier":["https://doi.org/10.7936/vfhm-j984","https://openscholarship.wustl.edu/eng_etds/486"],"dc:language":["English (en)"],"dc:rights":["I have not registered my thesis with the U.S. Copyright Office, but intend to later."],"dc:subject":["two-phase liquid cooling","micropillar","perimeter-to-area ratio","Particle Swarm Optimization algorithm","evaporation simulation","heat transfer coefficient","Computer-Aided Engineering and Design","Engineering","Heat Transfer, Combustion","Manufacturing"],"dc:title":["Enhanced Heat Transfer Performance by Shape Optimization of a Non-axisymmetric Droplet Evaporating on a Heated Micropillar"],"thesis:degree_discipline":["Mechanical Engineering & Materials Science","McKelvey School of Engineering"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["Master of Science (MS)"]},"updated_at":"2026-07-24T06:13:05Z"}