Two-phase immersion cooling for power dense printed circuit board converters
<p>This thesis presents research into two-phase immersion cooling with Novec 7000 dielectric fluid in sealed enclosures for power electronic converters on printed circuit board substrates. Pool boiling heat transfer is experimentally characterised at elevated saturation temperature and pressur...
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| Other Authors: | |
| Format: | Thesis |
| Language: | English |
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2024
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| _version_ | 1824458673322196992 |
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| author | Ristic-Smith, A |
| author2 | Rogers, D |
| author_facet | Rogers, D Ristic-Smith, A |
| author_sort | Ristic-Smith, A |
| collection | OXFORD |
| description | <p>This thesis presents research into two-phase immersion cooling with Novec 7000 dielectric fluid in sealed enclosures for power electronic converters on printed circuit board substrates. Pool boiling heat transfer is experimentally characterised at elevated saturation temperature and pressure on a flat planar surface representative of a semiconductor switch. Critical heat flux of 43W/cm2 is observed and the maximum heat transfer coefficient is 1.5W/(cm2 K). A theoretical model and numerical solution method for boiling on pin fins is developed and used to design heat spreaders to increase the power dissipation per unit semiconductor area with minimal penalty on the converter volume. A maximum switch level heat transfer coefficient of 2.5W/(cm2 K) is demonstrated experimentally. By grit-blasting the heat spreader surface, the switch level heat transfer coefficient increases to 3.4W/(cm2 K).</p>
<p>A sealed two-phase immersion cooling system design is proposed for an electric vehicle motor drive. The system could theoretically sustain power dissipation of 30W/(L K), which is competitive with the best performing systems in previous literature. The design facilitates integration of semiconductor switches, decoupling capacitors and gate drivers in close proximity on a single printed circuit board. This is an important step towards achieving power-dense PCB converters with low parasitic inductance electrical layouts.</p>
<p>Experiments with copper wires immersed in Novec 7000 indicate the maximum current-carrying capacity is up to eight times greater than for forced air cooling. Furthermore, it is shown that immersion of magnetic cores enables operation at high flux density and frequency. The volumetric power loss in a ferrite core is characterised at frequencies up to 1.6 MHz and flux densities up to saturation, a substantially wider operating range than is typically provided in material data-sheets. These results indicate it is possible to construct inductors and transformers with up to eight times smaller volume than those cooled by forced air. This is particularly important for applications like on-board chargers in electric vehicles, where compact magnetic components can lead to substantial reduction in volume for transformer isolated DC-DC converters.</p>
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| first_indexed | 2025-02-19T04:29:38Z |
| format | Thesis |
| id | oxford-uuid:3b70dd03-3db4-4134-8810-e54f2e25cd8d |
| institution | University of Oxford |
| language | English |
| last_indexed | 2025-02-19T04:29:38Z |
| publishDate | 2024 |
| record_format | dspace |
| spelling | oxford-uuid:3b70dd03-3db4-4134-8810-e54f2e25cd8d2024-12-19T12:21:45ZTwo-phase immersion cooling for power dense printed circuit board convertersThesishttp://purl.org/coar/resource_type/c_db06uuid:3b70dd03-3db4-4134-8810-e54f2e25cd8dPower electronicsHeat sinks (Electronics)EnglishHyrax Deposit2024Ristic-Smith, ARogers, D<p>This thesis presents research into two-phase immersion cooling with Novec 7000 dielectric fluid in sealed enclosures for power electronic converters on printed circuit board substrates. Pool boiling heat transfer is experimentally characterised at elevated saturation temperature and pressure on a flat planar surface representative of a semiconductor switch. Critical heat flux of 43W/cm2 is observed and the maximum heat transfer coefficient is 1.5W/(cm2 K). A theoretical model and numerical solution method for boiling on pin fins is developed and used to design heat spreaders to increase the power dissipation per unit semiconductor area with minimal penalty on the converter volume. A maximum switch level heat transfer coefficient of 2.5W/(cm2 K) is demonstrated experimentally. By grit-blasting the heat spreader surface, the switch level heat transfer coefficient increases to 3.4W/(cm2 K).</p> <p>A sealed two-phase immersion cooling system design is proposed for an electric vehicle motor drive. The system could theoretically sustain power dissipation of 30W/(L K), which is competitive with the best performing systems in previous literature. The design facilitates integration of semiconductor switches, decoupling capacitors and gate drivers in close proximity on a single printed circuit board. This is an important step towards achieving power-dense PCB converters with low parasitic inductance electrical layouts.</p> <p>Experiments with copper wires immersed in Novec 7000 indicate the maximum current-carrying capacity is up to eight times greater than for forced air cooling. Furthermore, it is shown that immersion of magnetic cores enables operation at high flux density and frequency. The volumetric power loss in a ferrite core is characterised at frequencies up to 1.6 MHz and flux densities up to saturation, a substantially wider operating range than is typically provided in material data-sheets. These results indicate it is possible to construct inductors and transformers with up to eight times smaller volume than those cooled by forced air. This is particularly important for applications like on-board chargers in electric vehicles, where compact magnetic components can lead to substantial reduction in volume for transformer isolated DC-DC converters.</p> |
| spellingShingle | Power electronics Heat sinks (Electronics) Ristic-Smith, A Two-phase immersion cooling for power dense printed circuit board converters |
| title | Two-phase immersion cooling for power dense printed circuit board converters |
| title_full | Two-phase immersion cooling for power dense printed circuit board converters |
| title_fullStr | Two-phase immersion cooling for power dense printed circuit board converters |
| title_full_unstemmed | Two-phase immersion cooling for power dense printed circuit board converters |
| title_short | Two-phase immersion cooling for power dense printed circuit board converters |
| title_sort | two phase immersion cooling for power dense printed circuit board converters |
| topic | Power electronics Heat sinks (Electronics) |
| work_keys_str_mv | AT risticsmitha twophaseimmersioncoolingforpowerdenseprintedcircuitboardconverters |