A Study of the Critical Conditions for Liquid Film Rupture by Flowing over a Hot Spot in a Vertical Plate
Date Issued
2009
Date
2009
Author(s)
Chiang, Chun-Liang
Abstract
A study for liquid free falling thin film rupture by flowing over a vertical plate which includes a hot spot. To investigate the thermocapillary effect due to the surface tension gradient that induces by non-uniform temperature distribution on the liquid thin film surface. A 3-mm diameter circular form hot spot was be used and found the water and 70% glycerine solution in water liquid film breakdown critical conditions. The range of critical heat flux that lead to film breakdown is 20~1860 kW/m2 and the liquid flow regimes are from pure laminar flow to stable wavy flow (Re= 0.2~55.2). According to the results which compared with references can prove that the heater length along the streamwise direction was shown to strongly effect the critical heat flux and the dynamics of liquid film breakdown. More short the heater length needs more large critical heat flux. Kabov et al. (1996) originally proposed that the direct measurements of the temperature field at the film surface using an infrared scanner revealed to that the film surface being great instability even ruptures when surface temperature gradients up to 10~15℃/mm. An experimental result from present data shown that is 11.4 ℃/mm and demonstrated the heater shape isn’t an important issue for film rupturing.
Subjects
free falling thin film
hot spot
breakdown
thermocapillary effect
critical heat flux
Type
thesis
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