STUDY OF CONDENSATION OF REFRIGERANTS IN MICRO-CHANNELS FOR DEVELOPMENT OF FUTURE COMPACT MICRO-CHANNEL CONDENSERS

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dc.contributor.advisorOhadi, Michaelen_US
dc.contributor.authorChowdhury, Souraven_US
dc.contributor.departmentMechanical Engineeringen_US
dc.contributor.publisherDigital Repository at the University of Marylanden_US
dc.contributor.publisherUniversity of Maryland (College Park, Md.)en_US
dc.date.accessioned2009-07-02T05:58:27Z
dc.date.available2009-07-02T05:58:27Z
dc.date.issued2008en_US
dc.description.abstractMini- and micro- channel technology has gained considerable ground in the recent years in industry and is favored due to its several advantages stemming from its high surface to volume ratio and high values of proof pressure it can withstand. Micro-channel technology has paved the way to development of highly compact heat exchangers with low cost and mass penalties. In the present work, the issues related to the sizing of compact micro-channel condensers have been explored. The considered designs encompass both the conventional and MEMS fabrication techniques. In case of MEMS-fabricated micro-channel condenser, wet etching of the micro-channel structures, followed by bonding of two such wafers with silicon nitride layers at the interface was attempted. It was concluded that the silicon nitride bonding requires great care in terms of high degree of surface flatness and absence of roughness and also high degree of surface purity and thus cannot be recommended for mass fabrication. Following this investigation, a carefully prepared experimental setup and test micro-channel with hydraulic diameter 700 microns and aspect ratio 7:1 was fabricated and overall heat transfer and pressure drop aspects of two condensing refrigerants, R134a and R245fa were studied at a variety of test conditions. To the best of author's knowledge, so far no data has been reported in the literature on condensation in such high aspect ratio micro-channels. Most of the published experimental works on condensation of refrigerants are concerning conventional hydraulic diameter channels (> 3mm) and only recently some experimental data has been reported in the sub-millimeter scale channels for which the surface tension and viscosity effects play a dominant role and the effect of gravity is diminished. It is found that both experimental data and empirically-derived correlations tend to under-predict the present data by an average of 25%. The reason for this deviation could be because a high aspect ratio channel tends to collect the condensate in the corners of its cross-section leaving only a thin liquid film on the flat side surfaces for better heat transfer than in circular or low aspect ratio channels.en_US
dc.format.extent4498056 bytes
dc.format.mimetypeapplication/pdf
dc.identifier.urihttp://hdl.handle.net/1903/9225
dc.language.isoen_US
dc.subject.pqcontrolledEngineering, Mechanicalen_US
dc.subject.pqcontrolledEngineering, Automotiveen_US
dc.subject.pqcontrolledEngineering, Aerospaceen_US
dc.subject.pquncontrolledCondensationen_US
dc.subject.pquncontrolledhigh aspect ratioen_US
dc.subject.pquncontrolledMicrochannelen_US
dc.subject.pquncontrolledR134aen_US
dc.subject.pquncontrolledR245faen_US
dc.subject.pquncontrolledSilicon Nitride Bondingen_US
dc.titleSTUDY OF CONDENSATION OF REFRIGERANTS IN MICRO-CHANNELS FOR DEVELOPMENT OF FUTURE COMPACT MICRO-CHANNEL CONDENSERSen_US
dc.typeDissertationen_US

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