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The Influence of Single Bubble Growth and Bubble Coalescence on Boiling Heat Transfer

Sielaff, Axel ; Stephan, Peter (2014)
The Influence of Single Bubble Growth and Bubble Coalescence on Boiling Heat Transfer.
Proceedings of the 15th International Heat Transfer Conference, IHTC-15. Kyoto, Japan (August 10-15, 2014)
Konferenzveröffentlichung, Bibliographie

Kurzbeschreibung (Abstract)

Boiling processes are widely used since decades. Nevertheless, the heat transfer phenomena are still not sufficiently understood. The subject of the presented work summarizes a generic experimental investigation of the boiling process performed for single and interacting bubbles at artificial cavities. Influences of these small scale events on the macroscopic boiling processes are discussed. The experimental setup consists of a 2-phase fluid container with FC-72 as working fluid. A thin stainless steel foil acts as Joule heater. Single or multiple bubbles are generated on top of the foil. Optical measurement techniques enable the measurement of the bubble’s shape and the temperature of the foil as well as the subsequent calculation of heat flux profiles. In case of single bubble nucleation a clear influence of the temperature of the heated surface just before the initial nucleation is observed. Depending on the conditions a liquid microlayer was formed or not, and the role of contact line evaporation versus microlayer evaporation changes. The experiments with bubble coalescences show a clear dependency of the coalescence frequency on the system pressure and the nucleation site distance. Probability distributions are derived. The evaluation of the transient heat flux profile during bubble coalescence shows, that the coalescence event leads to an increased heat transfer coefficient. However, these observations could not be confirmed on heaters with a large number of active artificial nucleation sites.

Typ des Eintrags: Konferenzveröffentlichung
Erschienen: 2014
Autor(en): Sielaff, Axel ; Stephan, Peter
Art des Eintrags: Bibliographie
Titel: The Influence of Single Bubble Growth and Bubble Coalescence on Boiling Heat Transfer
Sprache: Englisch
Publikationsjahr: 2014
Veranstaltungstitel: Proceedings of the 15th International Heat Transfer Conference, IHTC-15
Veranstaltungsort: Kyoto, Japan
Veranstaltungsdatum: August 10-15, 2014
Kurzbeschreibung (Abstract):

Boiling processes are widely used since decades. Nevertheless, the heat transfer phenomena are still not sufficiently understood. The subject of the presented work summarizes a generic experimental investigation of the boiling process performed for single and interacting bubbles at artificial cavities. Influences of these small scale events on the macroscopic boiling processes are discussed. The experimental setup consists of a 2-phase fluid container with FC-72 as working fluid. A thin stainless steel foil acts as Joule heater. Single or multiple bubbles are generated on top of the foil. Optical measurement techniques enable the measurement of the bubble’s shape and the temperature of the foil as well as the subsequent calculation of heat flux profiles. In case of single bubble nucleation a clear influence of the temperature of the heated surface just before the initial nucleation is observed. Depending on the conditions a liquid microlayer was formed or not, and the role of contact line evaporation versus microlayer evaporation changes. The experiments with bubble coalescences show a clear dependency of the coalescence frequency on the system pressure and the nucleation site distance. Probability distributions are derived. The evaluation of the transient heat flux profile during bubble coalescence shows, that the coalescence event leads to an increased heat transfer coefficient. However, these observations could not be confirmed on heaters with a large number of active artificial nucleation sites.

Fachbereich(e)/-gebiet(e): 16 Fachbereich Maschinenbau
16 Fachbereich Maschinenbau > Fachgebiet für Technische Thermodynamik (TTD)
Exzellenzinitiative
Exzellenzinitiative > Exzellenzcluster
Exzellenzinitiative > Exzellenzcluster > Center of Smart Interfaces (CSI)
Hinterlegungsdatum: 26 Aug 2016 09:19
Letzte Änderung: 08 Aug 2019 07:38
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