Investigation of contact line dynamics under a vapor bubble at boiling
on the transparent heater
A.S. Surtaev and V.S. Serdyukov
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
Novosibirsk State University, Novosibirsk, Russia
E-mail: surtaev@itp.nsc.ru
Keywords: boiling, microlayer, high-speed visualization, IR thermography, phase transitions
Abstract
The paper presents the results of an experimental study of dynamics of vapor bubble growth and departure at pool boiling, obtained with the use of high-speed video recording and IR thermography. The study was carried out at saturated water boiling under the atmospheric pressure in the range of heat fluxes of 30-150 kW/m2. To visualize the process and determine the
growth rates of the outer bubble diameter, microlayer region and dry spot area,
transparent thin film heater with the thickness of 1 μm deposited on sapphire substrate was used in the experiments, and video
recording was performed from the bottom side of the heating surface. To study
integral heat transfer as well as local non-stationary thermal characteristics,
high-speed infrared thermography with a frequency of up to 1000 FPS was used.
High-speed video recording showed that after formation of vapor bubble and
microlayer region, dry spot appears in a short time (up to 1 ms) under the
vapor bubble. Various stages of contact line boundary propagation were observed.
It was shown that at the initial stage before the development of small-scale
perturbations, the dry spot propagation rate is constant. It was also showed
that the bubble departure stage begins after complete evaporation of liquid
in the microlayer region.
DOI: 10.1134/S0869864318010067
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