Microchannel heat sinks for cooling high heat flux electronic devices―analysis with single and two phase flows

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dc.contributor.authorHegde, Pradeep Ganesh
dc.date.accessioned2014-11-03T02:25:27Z
dc.date.available2014-11-03T02:25:27Z
dc.date.issued2006
dc.descriptionPhDen_US
dc.description.abstractMicrochannel heat sinks constitute an innovative cooling technology for the efficient dissipation of the large amounts of heat from the very small and constrained areas of the high heat flux microelectronic chips and circuits. In the present study a general finite element model is developed to analyze microchannel heat sinks cooled by either single phase or two-phase flow. A 12 noded finite element is developed, which can be used to analyze a variety of microchannel heat sink configurations viz. single stack and multi-stack parallel and counter flow heat sinks cooled by single phase liquid or boiling two-phase flow. Convergence is typically obtained with about 15 assembled elements per stack for single-phase flow and with about 100 elements for two-phase flow. Consequently the method developed involves considerably less computational effort compared to conventional CFD methods. A MATLAB programme implementing the above FEM model executes within 20 seconds for single phase flow cooled heat sink and within one minute for two-phase flow cooled heat sink on a PC equipped with Pentium-4 chipset and 256 MB RAM. The present method also has the ability to handle cases of non-uniform base heat flux and coolant flow distributions. Additionally, a one dimensional finite element model trained artificial neural network is developed to determine two-phase flow pressure drop in microchannel heat sinks. It is observed from the study that a single stack counter flow heat sink yield better stream-wise temperature uniformity and lower thermal resistance of the order of 20 % for the configurations considered, than a similar parallel flow heat sink. All the analyses are done within the pumping power constraints of the present day micro and mini pumping technologies. With a view to achieve lower heat sink thermal resistances, microchannel heat sinks are analyzed using nanofluid coolants and the achievable percentage reduction in thermal resistance is documented. It is further observed that multi-stack heat sinks yield substantially lower thermal resistance and lower pressure drop than their single stack counterparts. Double stack counter flow heat sinks outperform parallel flow heat sinks at higher flow rates and uniform heat distributions providing upto 15% lower R for the configurations considered. Further, the heat sinks are also analyzed for different kinds of non-uniform base heat flux and coolant flow distributions. Microchannel heat sinks cooled by boiling two-phase flow yield excellent temperature uniformity and very low thermal resistances and pumping powers. Boiling flow of water and Fluroinert liquid FC-72 are considered for analyses. It is observed that for a given amount of heat removal two-phase flow heat sinks consume considerably less pumping power compared to single-phase cooled heat sinks. Twophase flow cooled single stack counter flow heat sinks and two-phase flow cooled multi-stack heat sinks are also analyzed. It is observed that counter flow two-phase cooled heat sinks yield better temperature uniformity and more than 20% lower thermal resistances than the parallel flow heat sinks for the configuration considered. Heat dissipations of the order of 1000 W with pumping power as low as 35 mW are demonstrated with double stack boiling water cooled heat sinks.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/294
dc.language.isoenen_US
dc.subjectScience Physicen_US
dc.subjectMicrochannel heat sinksen_US
dc.subjectElectronic devicesen_US
dc.titleMicrochannel heat sinks for cooling high heat flux electronic devices―analysis with single and two phase flowsen_US
dc.typeThesisen_US
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