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dc.contributor.authorChen, C. A.en_US
dc.contributor.authorChang, W. R.en_US
dc.contributor.authorLin, T. F.en_US
dc.date.accessioned2014-12-08T15:48:23Z-
dc.date.available2014-12-08T15:48:23Z-
dc.date.issued2010-09-01en_US
dc.identifier.issn0017-9310en_US
dc.identifier.urihttp://dx.doi.org/10.1016/j.ijheatmasstransfer.2010.02.038en_US
dc.identifier.urihttp://hdl.handle.net/11536/32229-
dc.description.abstractAn experiment is conducted here to investigate the effects of the imposed time periodic refrigerant flow rate oscillation in the form of nearly a triangular wave on refrigeriant R-134a flow boiling heat transfer and associated bubble characteristics in a horizontal narrow annular duct with the duct gap fixed at 2.0 mm. The results indicate that when the imposed heat flux is close to that for the onset of stable flow boiling, intermittent flow boiling appears in which nucleate boiling on the heated surface does not exist in an entire periodic cycle. At somewhat higher heat flux persistent boiling prevails. Besides, the refrigerant flow rate oscillation only slightly affects the time-average boiling curves and heat transfer coefficients. Moreover, the heated wall temperature, bubble departure diameter and frequency, and active nucleation site density are found to oscillate periodically in time as well and at the same frequency as the imposed mass flux oscillation. Furthermore, in the persistent boiling the resulting heated wall temperature oscillation is stronger for a longer period and a larger amplitude of the mass flux oscillation. And for a larger amplitude of the mass flux oscillation, stronger temporal oscillations in the bubble characteristics are noted. The effects of the mass flux oscillation on the size of the departing bubble and active nucleation site density dominate over the bubble departure frequency, causing the heated wall temperature to decrease and heat transfer coefficient to increase at reducing mass flux in the flow boiling, opposing to that in the single-phase flow. But they are only mildly affected by the period of the mass flux oscillation. However, a short time lag in the wall temperature oscillation is also noted. Finally, a flow regime map is provided to delineate the boundaries separating different boiling regimes for the R-134a flow boiling in the annular duct. (C) 2010 Published by Elsevier Ltd.en_US
dc.language.isoen_USen_US
dc.subjectTime periodic flow boilingen_US
dc.subjectR-134a boiling heat transferen_US
dc.subjectIntermittent boilingen_US
dc.subjectFlow rate oscillationen_US
dc.titleTime periodic flow boiling heat transfer of R-134a and associated bubble characteristics in a narrow annular duct due to flow rate oscillationen_US
dc.typeArticleen_US
dc.identifier.doi10.1016/j.ijheatmasstransfer.2010.02.038en_US
dc.identifier.journalINTERNATIONAL JOURNAL OF HEAT AND MASS TRANSFERen_US
dc.citation.volume53en_US
dc.citation.issue19-20en_US
dc.citation.spage3593en_US
dc.citation.epage3606en_US
dc.contributor.department機械工程學系zh_TW
dc.contributor.departmentDepartment of Mechanical Engineeringen_US
dc.identifier.wosnumberWOS:000280484400001-
dc.citation.woscount1-
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