{"id":{"repo_id":"umn","oai_identifier":"oai:conservancy.umn.edu:11299/174852"},"canonical_url":"https://search.dev.ndltd.org/etd/umn/oai:conservancy.umn.edu:11299/174852","repository":{"repo_id":"umn","name":"University of Minnesota","base_url":"https://conservancy.umn.edu/server/oai/request"},"display":{"title":"A Numerical Evaluation of Thermotropic Materials for Polymer Solar Thermal Collectors","abstract":"A series of numerical studies of thermotropic materials are conducted to develop a theoretical basis for the selection and design of phase change thermotropic materials for polymer collectors. The optical requirements for a thermotropic material to provide overheat protection are identified. In the clear state, high solar-weighted transmittance (≥80%, preferably ≥85%). To protect an absorber of polypropylene, material temperature limit of 115 �C, the solar-weighted reflectance of the thermotropic material must be ≥50%. To determine how to achieve these optical requirements, the radiative transfer within thermotropic materials is modeled with a Monte Carlo ray tracing algorithm. A parametric study of the radiative transfer in thermotropic materials is conducted. The results are presented as dimensionless plots of transmittance and reflectance as a function of the overall optical thickness τL, the scattering albedo ω, and the particle size parameter x. The study demonstrates that to achieve ≥85% transmittance in the clear state, the optical thickness must be low. To achieve ≥50% reflectance in the translucent state necessitates a significant increase in optical thickness with temperature. Additionally, the material must have small particles (x ≤ 2.5) and be weakly absorbing (ω ≥ 0.990). For example, for a size parameter of 2, the optical thickness in the clear state must be ≤0.35. The optical thickness in the translucent state must be ≥10 for a scattering albedo of 0.995. The data contained in these dimensionless plots can be used to identify and optimize thermotropic materials. A method for indentifying potential thermotropic material combinations is presented. Using encapsulated particles in a thermotropic material is also investigated. The transmittance and reflectance of hydroxystearic acid in poly(methyl methacrylate) are predicted as a function of shell refractive index, shell thickness, and particle volume fraction. The study demonstrates that a thermotropic material with encapsulated particles can achieve the optical requirements for use in a solar collector. Additionally, the study reveals that a wide range of shell relative refractive indices, from 0.95 to 1.0, and thicknesses, up to 35 nm, provide acceptable optical performance.","abstract_html":"A series of numerical studies of thermotropic materials are conducted to develop a theoretical basis for the selection and design of phase change thermotropic materials for polymer collectors. The optical requirements for a thermotropic material to provide overheat protection are identified. In the clear state, high solar-weighted transmittance (≥80%, preferably ≥85%). To protect an absorber of polypropylene, material temperature limit of 115 �C, the solar-weighted reflectance of the thermotropic material must be ≥50%. To determine how to achieve these optical requirements, the radiative transfer within thermotropic materials is modeled with a Monte Carlo ray tracing algorithm. A parametric study of the radiative transfer in thermotropic materials is conducted. The results are presented as dimensionless plots of transmittance and reflectance as a function of the overall optical thickness τL, the scattering albedo ω, and the particle size parameter x. The study demonstrates that to achieve ≥85% transmittance in the clear state, the optical thickness must be low. To achieve ≥50% reflectance in the translucent state necessitates a significant increase in optical thickness with temperature. Additionally, the material must have small particles (x ≤ 2.5) and be weakly absorbing (ω ≥ 0.990). For example, for a size parameter of 2, the optical thickness in the clear state must be ≤0.35. The optical thickness in the translucent state must be ≥10 for a scattering albedo of 0.995. The data contained in these dimensionless plots can be used to identify and optimize thermotropic materials. A method for indentifying potential thermotropic material combinations is presented. Using encapsulated particles in a thermotropic material is also investigated. The transmittance and reflectance of hydroxystearic acid in poly(methyl methacrylate) are predicted as a function of shell refractive index, shell thickness, and particle volume fraction. The study demonstrates that a thermotropic material with encapsulated particles can achieve the optical requirements for use in a solar collector. Additionally, the study reveals that a wide range of shell relative refractive indices, from 0.95 to 1.0, and thicknesses, up to 35 nm, provide acceptable optical performance.","abstract_has_math":false,"creators":["Gladen, Adam"],"institution":null,"degree_name":null,"degree_level":null,"degree_discipline":null,"degree_department":null,"school":null,"contributors":[],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2014,"date_issued":"2014-07","date_published":"2014-07","updated_at":"2026-07-24T05:20:07Z","subjects":["Overheat Protection","Polymer Collector","Thermotropic"],"languages":["en"],"rights":[],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"http://hdl.handle.net/11299/174852","outbound_label":"Handle","outbound_source":"dc:identifier.uri"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:creator","label":"Author","values":["Gladen, Adam"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date.accessioned","label":"Dc Date Accessioned","values":["2015-10-13T18:53:48Z"]},{"key":"dc:date.available","label":"Dc Date Available","values":["2015-10-13T18:53:48Z"]},{"key":"dc:date.issued","label":"Date","values":["2014-07"]},{"key":"dc:type","label":"Dc Type","values":["Thesis or Dissertation"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Overheat Protection","Polymer Collector","Thermotropic"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language.iso","label":"Language (ISO)","values":["en"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier.uri","label":"Identifier URI","values":["http://hdl.handle.net/11299/174852"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["University of Minnesota Ph.D. dissertation. July 2014. Major: Mechanical Engineering. Advisors: Susan Mantell, Jane Davidson. 1 computer file (PDF); xvi, 179 pages."]},{"key":"dc:description.abstract","label":"Abstract","values":["A series of numerical studies of thermotropic materials are conducted to develop a theoretical basis for the selection and design of phase change thermotropic materials for polymer collectors. The optical requirements for a thermotropic material to provide overheat protection are identified. In the clear state, high solar-weighted transmittance (≥80%, preferably ≥85%). To protect an absorber of polypropylene, material temperature limit of 115 �C, the solar-weighted reflectance of the thermotropic material must be ≥50%. To determine how to achieve these optical requirements, the radiative transfer within thermotropic materials is modeled with a Monte Carlo ray tracing algorithm. A parametric study of the radiative transfer in thermotropic materials is conducted. The results are presented as dimensionless plots of transmittance and reflectance as a function of the overall optical thickness τL, the scattering albedo ω, and the particle size parameter x. The study demonstrates that to achieve ≥85% transmittance in the clear state, the optical thickness must be low. To achieve ≥50% reflectance in the translucent state necessitates a significant increase in optical thickness with temperature. Additionally, the material must have small particles (x ≤ 2.5) and be weakly absorbing (ω ≥ 0.990). For example, for a size parameter of 2, the optical thickness in the clear state must be ≤0.35. The optical thickness in the translucent state must be ≥10 for a scattering albedo of 0.995. The data contained in these dimensionless plots can be used to identify and optimize thermotropic materials. A method for indentifying potential thermotropic material combinations is presented. Using encapsulated particles in a thermotropic material is also investigated. The transmittance and reflectance of hydroxystearic acid in poly(methyl methacrylate) are predicted as a function of shell refractive index, shell thickness, and particle volume fraction. The study demonstrates that a thermotropic material with encapsulated particles can achieve the optical requirements for use in a solar collector. Additionally, the study reveals that a wide range of shell relative refractive indices, from 0.95 to 1.0, and thicknesses, up to 35 nm, provide acceptable optical performance."]},{"key":"dc:title","label":"Title","values":["A Numerical Evaluation of Thermotropic Materials for Polymer Solar Thermal Collectors"]}]}],"canonical_facts":{"dc:creator":["Gladen, Adam"],"dc:date.accessioned":["2015-10-13T18:53:48Z"],"dc:date.available":["2015-10-13T18:53:48Z"],"dc:date.issued":["2014-07"],"dc:description":["University of Minnesota Ph.D. dissertation. July 2014. Major: Mechanical Engineering. Advisors: Susan Mantell, Jane Davidson. 1 computer file (PDF); xvi, 179 pages."],"dc:description.abstract":["A series of numerical studies of thermotropic materials are conducted to develop a theoretical basis for the selection and design of phase change thermotropic materials for polymer collectors. The optical requirements for a thermotropic material to provide overheat protection are identified. In the clear state, high solar-weighted transmittance (≥80%, preferably ≥85%). To protect an absorber of polypropylene, material temperature limit of 115 �C, the solar-weighted reflectance of the thermotropic material must be ≥50%. To determine how to achieve these optical requirements, the radiative transfer within thermotropic materials is modeled with a Monte Carlo ray tracing algorithm. A parametric study of the radiative transfer in thermotropic materials is conducted. The results are presented as dimensionless plots of transmittance and reflectance as a function of the overall optical thickness τL, the scattering albedo ω, and the particle size parameter x. The study demonstrates that to achieve ≥85% transmittance in the clear state, the optical thickness must be low. To achieve ≥50% reflectance in the translucent state necessitates a significant increase in optical thickness with temperature. Additionally, the material must have small particles (x ≤ 2.5) and be weakly absorbing (ω ≥ 0.990). For example, for a size parameter of 2, the optical thickness in the clear state must be ≤0.35. The optical thickness in the translucent state must be ≥10 for a scattering albedo of 0.995. The data contained in these dimensionless plots can be used to identify and optimize thermotropic materials. A method for indentifying potential thermotropic material combinations is presented. Using encapsulated particles in a thermotropic material is also investigated. The transmittance and reflectance of hydroxystearic acid in poly(methyl methacrylate) are predicted as a function of shell refractive index, shell thickness, and particle volume fraction. The study demonstrates that a thermotropic material with encapsulated particles can achieve the optical requirements for use in a solar collector. Additionally, the study reveals that a wide range of shell relative refractive indices, from 0.95 to 1.0, and thicknesses, up to 35 nm, provide acceptable optical performance."],"dc:identifier.uri":["http://hdl.handle.net/11299/174852"],"dc:language.iso":["en"],"dc:subject":["Overheat Protection","Polymer Collector","Thermotropic"],"dc:title":["A Numerical Evaluation of Thermotropic Materials for Polymer Solar Thermal Collectors"],"dc:type":["Thesis or Dissertation"]},"updated_at":"2026-07-24T05:20:07Z"}