Please use this identifier to cite or link to this item: http://bura.brunel.ac.uk/handle/2438/6600
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dc.contributor.advisorKarayiannis, TG-
dc.contributor.advisorKenning, DBR-
dc.contributor.advisorLewis, JS-
dc.contributor.authorAhmad, Syed Waqas-
dc.date.accessioned2012-08-08T09:22:26Z-
dc.date.available2012-08-08T09:22:26Z-
dc.date.issued2012-
dc.identifier.urihttp://bura.brunel.ac.uk/handle/2438/6600-
dc.descriptionThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.en_US
dc.description.abstractThe effect of surface modification and high intensity electric field (uniform and non – uniform) acting separately or in combination on pool boiling of R-123 is presented in this thesis. The effect of surface modification was investigated on saturated pool boiling of R-123 for five horizontal copper surfaces modified by different treatments, namely: an emery polished surface, a fine sandblasted surface, a rough sandblasted surface, an electron beam (EB) enhanced surface and a sintered surface. Each 40 mm diameter heating surface formed the upper face of an oxygen-free copper block, electrically heated by embedded cartridge heaters. The experiments were performed from the convective heat transfer regime to the critical heat flux, with both increasing and decreasing heat flux, at 1.01 bar, and additionally at 2 bar and 4 bar for the emery polished surface. Significant enhancement of heat transfer with increasing surface modification was demonstrated, particularly for the EB enhanced and sintered surfaces. The emery polished and sandblasted surface results are compared with nucleate boiling correlations and other published data. The effect of uniform and non-uniform electric fields on saturated pool boiling of R-123 at 1.01 bar pressure was also examined. This method of heat transfer enhancement is known as electrohydrodynamic abbreviated as EHD-enhancement. A high voltage potential was applied at the electrode located above the heating surface, which was earthed. The voltage was varied from 0 to 30 kV. The uniform electric field was provided through a 40 mm diameter circular electrode of stainless steel 304 wire mesh having an aperture of 5.1 mm, while the non-uniform electric field was obtained by using a 40 mm diameter circular rod electrode with rods 5 and 8 mm apart. The effect of uniform electric field was investigated using all five modified surfaces, i.e. emery polished, fine sandblasted, rough sandblasted, EB enhanced and sintered surfaces, while non – uniform electric field was tested using the emery polished, fine sandblasted, EB enhanced and sintered surfaces. The effect of pressure on EHD enhancement was also examined using emery polished surface at saturation pressure of 2 and 4 bars while the electric field was fix at 20 kV corresponding to 2 MV/m. Further, the bubble dynamics is presented for the emery polished surface obtained using a high-speed high – resolution camera.en_US
dc.description.sponsorshipThe Government of Pakistanen_US
dc.language.isoenen_US
dc.publisherBrunel University School of Engineering and Design PhD Theses-
dc.relation.requireshttp://bura.brunel.ac.uk/bitstream/2438/6600/1/FullTextThesis.docx-
dc.relation.urihttp://bura.brunel.ac.uk/bitstream/2438/6600/3/FulltextThesis.pdf-
dc.subjectAverage surface roughnessen_US
dc.subjectElectrohydrodynamicsen_US
dc.subjectHeat transfer enhancementen_US
dc.subjectCompound heat transfer enhancementen_US
dc.subjectBubble dynamicsen_US
dc.titleCombined effect of electric field and surface modification on pool boiling of R-123en_US
dc.typeThesisen_US
Appears in Collections:Brunel University Theses
Mechanical and Aerospace Engineering
Dept of Mechanical and Aerospace Engineering Theses

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