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ホーム アーカイブ 役員 今後の会合 American Society of Thermal and Fluids Engineering

A COMBINED EXPERIMENTAL AND COMPUTATIONAL STUDY OF THE HEAT TRANSFER CHARACTERISTICS OF FALLING LIQUID-FILMS

Alexandros Charogiannis
Clean Energy Processes (CEP) Laboratory, Department of Chemical Engineering, Imperial College London, London SW7 2AZ, United Kingdom

Fabian Denner
Department of Mechanical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom

Berend G. M. van Wachem
Formerly at the Department of Mechanical Engineering, Imperial College London, SW7 2AZ, UK; Lehrstuhl für Technische Thermodynamik, Otto-von-Guericke-Universität Magdeburg, 39106 Germany

Serafim Kaliadasis
Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom

Christos N. Markides
Clean Energy Processes (CEP) Laboratory, Department of Chemical Engineering, Imperial College London, South Kensington Campus, London SW7 2AZ, United Kingdom

DOI: 10.1615/TFEC2018.fmp.021505
pages 985-994


キーワード: Film flows, Unsteady heat transfer, Heat transfer coefficient, Laser-induced fluorescence, Particle tracking velocimetry, Infrared thermography, Direct numerical simulations

要約

An optical technique that combines planar laser-induced fluorescence (PLIF), particle tracking velocimetry (PTV) and infrared thermography (IR) was applied for the investigation of the hydrodynamic and heat transfer characteristics of harmonically-excited liquid films falling under the action of gravity over an inclined, electrically heated glass-substrate. PLIF was used to recover film-height data, PTV to recover two-dimensional (2D) velocity-field data, and IR to recover the temperature of the gas-liquid interface. The experiments were complemented by direct numerical simulations (DNSs) that provide additional information on the liquid viscosity, temperature and velocity distributions between the flow inlet and the downstream location where the optical measurements were collected. By adoption of this synergistic approach we recover a wealth of information, including novel results on the spatiotemporal evolution of the interface topology, and the flow and temperature fields underneath the wavy interface. Based on this data we also deduce local and instantaneous heat transfer coefficients (HTCs), and focus our efforts towards the investigation of two HTC-enhancement mechanisms; the observation of "hot-spots" as precursors to the formation of thermal rivulets, which can result in local enhancements in excess of 50%, and the presence of large velocity components in the crossstream direction of the flow, which promote mixing and are shown to improve heat transfer by up to ~ 7% compared to flow regions of the same height.

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