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Thermal bubble behaviour in liquid nitrogen under electric fields

Thermal bubble behaviour in liquid nitrogen under electric fields
Thermal bubble behaviour in liquid nitrogen under electric fields
This thesis describes thermally induced bubble behaviour changes in liquid nitrogen (LN2) under electric fields. Cryogenic liquids such as LN2 have been used not only as the coolant but also as the electrical insulator in superconducting and cryogenic apparatus. However, bubbles are easily formed in these liquids by even moderate heating because of a narrow liquid temperature range and low boiling point. Bubbles are considered to be one of the factors causing a reduction of the electrical insulation level. Consequently, bubble behaviour in electric fields is of great interest primarily in the study of prebreakdown and breakdown phenomena in the presence of thermally induced bubbles. In addition, a bubble can appear and its behaviour changes in a fluid under the influence of an electric field, and this is the main reason for boiling heat transfer enhancement which is related to thermal stability and heat transfer efficiency.
Studies including single bubble behaviour and bubble column behaviour as well as boiling heat transfer enhancement due to changes in bubble behaviour under electric fields using different electrodes have been completed. Free thermal bubble motion and related characteristics in LN2 under a conductor-plane electrode have been experimentally studied. A model for bubble motion in this non-uniform electric field has been developed and is described. Compared with theoretical results, the experimental measurements are in good agreement. An rimental study into the behaviour of thermal bubbles between two plane-plane inclined electrodes has been completed. Using a stainless steel mesh-to-plane electrode system, experimental investigations have been carried out to study the effect of uniform dc electric fields on the behaviour of a single thermal bubble in LN2. Bubble characteristics such as bubble growth, deformation and bubble departure frequency have been experimentally evaluated. Finally, the electric field effects on boiling heat transfer of LN2 have been experimentally assessed. The obtained data is applicable to the design of LN2 cooled high temperature superconductor power apparatus for both coolant and electrical insulation issues.
Wang, Ping
5f7a5780-5969-4486-ab0c-c527e48b3c34
Wang, Ping
5f7a5780-5969-4486-ab0c-c527e48b3c34
Lewin, Paul
78b4fc49-1cb3-4db9-ba90-3ae70c0f639e
Chen, George
3de45a9c-6c9a-4bcb-90c3-d7e26be21819

Wang, Ping (2008) Thermal bubble behaviour in liquid nitrogen under electric fields. University of Southampton, School of Electronics and Computer Science, Doctoral Thesis, 172pp.

Record type: Thesis (Doctoral)

Abstract

This thesis describes thermally induced bubble behaviour changes in liquid nitrogen (LN2) under electric fields. Cryogenic liquids such as LN2 have been used not only as the coolant but also as the electrical insulator in superconducting and cryogenic apparatus. However, bubbles are easily formed in these liquids by even moderate heating because of a narrow liquid temperature range and low boiling point. Bubbles are considered to be one of the factors causing a reduction of the electrical insulation level. Consequently, bubble behaviour in electric fields is of great interest primarily in the study of prebreakdown and breakdown phenomena in the presence of thermally induced bubbles. In addition, a bubble can appear and its behaviour changes in a fluid under the influence of an electric field, and this is the main reason for boiling heat transfer enhancement which is related to thermal stability and heat transfer efficiency.
Studies including single bubble behaviour and bubble column behaviour as well as boiling heat transfer enhancement due to changes in bubble behaviour under electric fields using different electrodes have been completed. Free thermal bubble motion and related characteristics in LN2 under a conductor-plane electrode have been experimentally studied. A model for bubble motion in this non-uniform electric field has been developed and is described. Compared with theoretical results, the experimental measurements are in good agreement. An rimental study into the behaviour of thermal bubbles between two plane-plane inclined electrodes has been completed. Using a stainless steel mesh-to-plane electrode system, experimental investigations have been carried out to study the effect of uniform dc electric fields on the behaviour of a single thermal bubble in LN2. Bubble characteristics such as bubble growth, deformation and bubble departure frequency have been experimentally evaluated. Finally, the electric field effects on boiling heat transfer of LN2 have been experimentally assessed. The obtained data is applicable to the design of LN2 cooled high temperature superconductor power apparatus for both coolant and electrical insulation issues.

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Published date: October 2008
Organisations: University of Southampton

Identifiers

Local EPrints ID: 64874
URI: http://eprints.soton.ac.uk/id/eprint/64874
PURE UUID: 3aae05cc-154a-499d-b0db-0b63e3ef6de8
ORCID for Paul Lewin: ORCID iD orcid.org/0000-0002-3299-2556

Catalogue record

Date deposited: 20 Jan 2009
Last modified: 16 Mar 2024 02:41

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Contributors

Author: Ping Wang
Thesis advisor: Paul Lewin ORCID iD
Thesis advisor: George Chen

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