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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-421-2

International Heat Transfer Conference 15
August, 10-15, 2014, Kyoto, Japan

Evaporation, Dynamics and Crisis Phenomena in Thin Liquid Films Sheared by Gas in a Narrow Channel

Get access (open in a dialog) DOI: 10.1615/IHTC15.flm.009537
pages 3347-3361

要約

In the present paper, we investigate the dynamics and heat transfer of evaporating locally heated thin liquid film driven by the action of the flow in a narrow channel. Experiments with water and FC-72 in flat channels (height 1.2-2.0 mm) were conducted. Maps of flow subregimes for shear-driven film were plotted. A stable stratified flow subregime exists in minichannels with width of 40 mm. CHF for a shear driven film may be up to 10 times higher than that for a falling liquid film, and reaches more than 400 W/cm2 in experiments with water. CHF increases with the and liquid flow rates. The longitudinal micro-fins with the height of 0.3 and 0.5 mm may increase CHF by a factor of 3. Experimental investigations were supplemented with the theoretical one. Two-sided three dimensional mathematical model is used to study interaction and balancing of different effects on the evaporation process along the liquid interface and film deformations. For a deformable gas-liquid interface, convection heat transfer in the liquid and the gas phases as well as temperature dependence of surface tension and liquid viscosity are taken into account. An influence of the gas flow rate and heating intensity were investigated numerically. It is shown that mainly evaporation takes place in the vicinity of the heater. The minimum film thickness takes place near the end of the heater. Even at quite low heating intensities transversal deformations become significant and longitudinal deformations of the gas-liquid interface could be much smaller in comparison with them. The longitudinal deformations depend significantly on the value of the gas Reynolds number.