{"id":{"repo_id":"uiuc","oai_identifier":"oai:www.ideals.illinois.edu:2142/130059"},"canonical_url":"https://search.dev.ndltd.org/etd/uiuc/oai:www.ideals.illinois.edu:2142/130059","repository":{"repo_id":"uiuc","name":"University of Illinois - Urbana-Champaign","base_url":"https://www.ideals.illinois.edu/oai-pmh"},"display":{"title":"Measurement limits and performance analysis of multilayer insulation under vacuum and cryogenic temperatures using a modified calorimeter-bar setup","abstract":"Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2027-08-01","abstract_html":"Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2027-08-01","abstract_has_math":false,"creators":["Joshi, Saptarshi Yogesh"],"institution":"University of Illinois Urbana-Champaign","degree_name":"M.S.","degree_level":"Thesis","degree_discipline":"Mechanical Engineering","degree_department":null,"school":null,"contributors":["Miljkovic, Nenad"],"advisors":[],"committee_chairs":[],"committee_members":[],"year":2025,"date_issued":"2025-07-23","date_published":"2025-07-23","updated_at":"2026-07-22T22:25:06Z","subjects":["Multilayer Insulation","Thermal Characterization","Cryogenics","Thermal Conductivity Measurement"],"languages":["en","eng"],"rights":["Copyright 2025 Saptarshi Joshi"],"rights_urls":[],"identifier_entries":[]},"links":{"outbound_url":"https://hdl.handle.net/2142/130059","outbound_label":"Handle","outbound_source":"dc:identifier"},"metadata_groups":[{"id":"people","label":"People","entries":[{"key":"dc:contributor","label":"Contributor","values":["Miljkovic, Nenad"]},{"key":"dc:creator","label":"Author","values":["Joshi, Saptarshi Yogesh"]}]},{"id":"academic_context","label":"Academic Context","entries":[{"key":"dc:date","label":"Dc Date","values":["2025-07-23","2025-08"]},{"key":"dc:type","label":"Dc Type","values":["text"]},{"key":"thesis:degree_discipline","label":"Discipline","values":["Mechanical Engineering"]},{"key":"thesis:degree_level","label":"Degree Level","values":["Thesis"]},{"key":"thesis:degree_name","label":"Degree Name","values":["M.S."]},{"key":"thesis:institution_name","label":"Thesis Institution Name","values":["University of Illinois Urbana-Champaign"]}]},{"id":"subjects_keywords","label":"Subjects and Keywords","entries":[{"key":"dc:subject","label":"Dc Subject","values":["Multilayer Insulation","Thermal Characterization","Cryogenics","Thermal Conductivity Measurement"]}]},{"id":"language_rights","label":"Language and Rights","entries":[{"key":"dc:language","label":"Dc Language","values":["en","eng"]},{"key":"dc:rights","label":"Dc Rights","values":["Copyright 2025 Saptarshi Joshi"]}]},{"id":"identifiers","label":"Identifiers","entries":[{"key":"dc:identifier","label":"Identifier","values":["https://hdl.handle.net/2142/130059"]}]},{"id":"additional","label":"Additional Metadata","entries":[{"key":"dc:description","label":"Description","values":["Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2027-08-01","The student, Saptarshi Joshi, accepted the attached license on 2025-07-21 at 19:43.","The student, Saptarshi Joshi, submitted this Thesis for approval on 2025-07-21 at 19:56.","This Thesis was approved for publication on 2025-07-23 at 15:00.","DSpace SAF Submission Ingestion Package generated from Vireo submission #22684 on 2025-10-21 at 10:06:18","High-performance cryogenic electric machines, such as superconducting motors, require exceptional thermal insulation to minimize heat leakage and maintain operational temperatures below 50 K. Multilayer insulation (MLI) is widely used in such systems due to its low thermal conductance, but its performance is highly sensitive to contact pressure, vacuum level, and structural configuration—making accurate experimental characterization essential. This thesis presents the design, development, and implementation of a modified ASTM D5470-based one-dimensional (1D) calorimeter bar apparatus to measure the through-thickness thermal conductance of MLI under vacuum at both ambient and cryogenic temperatures. The apparatus integrates mirror-polished metal bars, high-precision temperature sensing, and a high-vacuum chamber to enable controlled steady-state heat flow through MLI samples. Cryogenic conditions were achieved using both liquid nitrogen and a cryocooler-thermal strap system. Experimental results at ambient temperatures showed that stainless steel bars provided improved measurement reliability due to steeper axial temperature gradients. Tests at cryogenic temperatures demonstrated clear trends in conductance with respect to layer count, compression, and shielding, but failed to reach the ultra-low conductance values theoretically expected of high-performance MLI. Analytical modeling and uncertainty analysis revealed that lateral radiative losses and shallow temperature gradients led to significant overestimation of true conductance at low flux levels. The results indicate that while the adapted calorimeter bar method is suitable for moderate conductance characterization, its current configuration imposes a practical resolution limit near 1 W/m²·K. This study establishes both the capabilities and limitations of the ASTM D5470 method for cryogenic MLI evaluation and informs future designs for ultra-low conductance measurement systems."]},{"key":"dc:format","label":"Dc Format","values":["application/pdf"]},{"key":"dc:title","label":"Title","values":["Measurement limits and performance analysis of multilayer insulation under vacuum and cryogenic temperatures using a modified calorimeter-bar setup"]}]}],"canonical_facts":{"dc:contributor":["Miljkovic, Nenad"],"dc:creator":["Joshi, Saptarshi Yogesh"],"dc:date":["2025-07-23","2025-08"],"dc:description":["Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2027-08-01","The student, Saptarshi Joshi, accepted the attached license on 2025-07-21 at 19:43.","The student, Saptarshi Joshi, submitted this Thesis for approval on 2025-07-21 at 19:56.","This Thesis was approved for publication on 2025-07-23 at 15:00.","DSpace SAF Submission Ingestion Package generated from Vireo submission #22684 on 2025-10-21 at 10:06:18","High-performance cryogenic electric machines, such as superconducting motors, require exceptional thermal insulation to minimize heat leakage and maintain operational temperatures below 50 K. Multilayer insulation (MLI) is widely used in such systems due to its low thermal conductance, but its performance is highly sensitive to contact pressure, vacuum level, and structural configuration—making accurate experimental characterization essential. This thesis presents the design, development, and implementation of a modified ASTM D5470-based one-dimensional (1D) calorimeter bar apparatus to measure the through-thickness thermal conductance of MLI under vacuum at both ambient and cryogenic temperatures. The apparatus integrates mirror-polished metal bars, high-precision temperature sensing, and a high-vacuum chamber to enable controlled steady-state heat flow through MLI samples. Cryogenic conditions were achieved using both liquid nitrogen and a cryocooler-thermal strap system. Experimental results at ambient temperatures showed that stainless steel bars provided improved measurement reliability due to steeper axial temperature gradients. Tests at cryogenic temperatures demonstrated clear trends in conductance with respect to layer count, compression, and shielding, but failed to reach the ultra-low conductance values theoretically expected of high-performance MLI. Analytical modeling and uncertainty analysis revealed that lateral radiative losses and shallow temperature gradients led to significant overestimation of true conductance at low flux levels. The results indicate that while the adapted calorimeter bar method is suitable for moderate conductance characterization, its current configuration imposes a practical resolution limit near 1 W/m²·K. This study establishes both the capabilities and limitations of the ASTM D5470 method for cryogenic MLI evaluation and informs future designs for ultra-low conductance measurement systems."],"dc:format":["application/pdf"],"dc:identifier":["https://hdl.handle.net/2142/130059"],"dc:language":["en","eng"],"dc:rights":["Copyright 2025 Saptarshi Joshi"],"dc:subject":["Multilayer Insulation","Thermal Characterization","Cryogenics","Thermal Conductivity Measurement"],"dc:title":["Measurement limits and performance analysis of multilayer insulation under vacuum and cryogenic temperatures using a modified calorimeter-bar setup"],"dc:type":["text"],"thesis:degree_discipline":["Mechanical Engineering"],"thesis:degree_level":["Thesis"],"thesis:degree_name":["M.S."],"thesis:institution_name":["University of Illinois Urbana-Champaign"]},"updated_at":"2026-07-22T22:25:06Z"}