Microwave defrosting on a metal substrate

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Mechanical Engineering

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2022

Author dc:creator

• Kim, John Jongwoo

Contributors dc:contributor

• Brewster, M. Quinn
• Glumac, Nick G.
• Wang, Xinlei
• Wang, Sophie

• Defrosting, Microwave

Statement dc:rights

• Copyright 2021 John Kim

Language dc:language

en

Handle dc:identifier

http://hdl.handle.net/2142/112951

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/112951