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Início Arquivos Thermal Letter Representantes Futuras reuniões Assembléia das Conferências Internacionais de Transferência de Calor
International Heat Transfer Conference 15

ISSN: 2377-424X (online)
ISSN: 2377-4371 (flashdrive)

High Resolution Heat Transfer Measurements at the Three Phase Contact Line of a Moving Single Meniscus

Sebastian Fischer
Institute for Technical Thermodynamics, Technische Universitat Darmstadt

Stefan Batzdorf
Institute for Technical Thermodynamics, Technische Universitat Darmstadt

Tatiana Gambaryan-Roisman
Technische Universität Darmstadt

Peter Stephan
Institute for Technical Thermodynamics, Technische Universität Darmstadt, 64287 Darmstadt, Germany

DOI: 10.1615/IHTC15.tdy.008230
pages 7785-7796


Palavras-chave: Thermodynamics, Boiling and evaporation, Heat transfer, Three phase contact line, IR thermography

Resumo

In the present work the influences of contact line velocity and direction, as well as system pressure on the local heat transfer characteristics in the vicinity of the three phase contact line are investigated experimentally. The test facility provides a single liquid-vapour meniscus in a well-controlled saturated atmosphere. Carefully degassed, thus pure fluorinert liquid PF-5060 is used as working fluid. The meniscus is positioned in a capillary slot of 1.4 mm width between an isothermal polished copper wall on one side and a heater wall on the opposite side. The heater wall consists of an infrared-transparent substrate coated with a thin metallic double-layer. This allows well-controlled heat supply to the 2-phase fluid and accurate measurement of the temperature field extremely close (approx. 800 nm) to the heater/fluid-interface using IR thermography with high spatial and temporal resolution. From the 2-dimensional temperature fields, the local heat flux distribution is calculated. A fluid displacement system enables a controlled movement of the meniscus in the capillary slot, thus simulating advancing or receding contact line situations with controlled velocities. The presented results clearly show that and how the local heat transfer distribution depends on the contact line velocity and direction. In the situation of an accelerated receding liquid/vapour-interface the moving meniscus leaves behind a thin liquid layer at the wall, while it leaves behind a dry wall, when receding with a constant velocity. In the first case heat transfer is dominated by thin film or microlayer evaporation, while in the second case it is governed by contact line evaporation. These generic results can explain similar observations in different boiling regimes.

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