2026-09-20T19:19:39Z https://www.ideals.illinois.edu/oai-pmh

oai:www.ideals.illinois.edu:2142/112951 2023-07-11 col_2142_5131 col_2142_14787 com_2142_5130 com_2142_9630 com_2142_234

Brewster, M. Quinn Brewster, M. Quinn Glumac, Nick G. Wang, Xinlei Wang, Sophie Kim, John Jongwoo 2022-01-12T21:40:31Z 2022-01-12T21:40:31Z 2021-05-28 2021-08 Microwave defrosting on a metal substrate was investigated theoretically and experimentally for application to refrigerator evaporator coils. Methods to improve the intrinsically poor microwave absorptivity of frost-on-metal substrate were explored. Experimentation was done to eliminate the tendency of metals with sharp edges to cause arcing in a microwave field. This was accomplished by adjusting the capacitance of the magnetron circuit and reducing the overall power from 600 W to 186 W.A one-dimensional finite element model was developed to predict the temperature profile in the frost during the defrosting process. The governing equations included a time-dependent source term corresponding to the absorption of microwave power. The intrinsic spatial non uniformity of defrosting was also investigated. Results showed that microwave defrosting is a feasible and effective method over traditional electrical/convecting heating. Comparison of a 200W electrical heater and 186 W microwave system showed that microwave heating provides uniform and energy-efficient defrosting while keeping the surrounding air and material temperatures relatively low during the process. Microwave energy penetrates the frost and warms the entire volume simultaneously, achieving more uniform temperature increase than with convective heating. In addition, the evaporator surface exposed by frost melting does not overheat with microwave defrosting since metals are highly reflective to microwaves. Submission original under an indefinite embargo labeled 'Open Access'. The submission was exported from vireo on 2022-01-12 without embargo terms The student, John Kim, accepted the attached license on 2021-05-21 at 12:45. The student, John Kim, submitted this Dissertation for approval on 2021-05-21 at 12:57. This Dissertation was approved for publication on 2021-05-28 at 10:08. DSpace SAF Submission Ingestion Package generated from Vireo submission #16653 on 2022-01-12 at 12:42:46 Made available in DSpace on 2022-01-12T21:40:31Z (GMT). No. of bitstreams: 3 KIM-DISSERTATION-2021.pdf: 2980267 bytes, checksum: 9b4c511f39c6b96d47e6e49f4f1027b1 (MD5) JWKimPhDdissertationv_Final.docx: 6860049 bytes, checksum: aa529ecfd93143aa6345f3c8601f1323 (MD5) LICENSE.txt: 4205 bytes, checksum: cdb5ff0b63663242b951d1abff461931 (MD5) Previous issue date: 2021-05-28 application/pdf http://hdl.handle.net/2142/112951 en Copyright 2021 John Kim Defrosting, Microwave Microwave defrosting on a metal substrate text Thesis Mechanical Sci & Engineering Mechanical Engineering University of Illinois at Urbana-Champaign Dissertation Ph.D.