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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

CHARACTERISTICS OF A SOLITARY VAPOR BUBBLE UNDER SUBCOOLED WATER BOILING

Get access (open in a dialog) DOI: 10.1615/IHTC16.bae.023598
pages 963-970

Resumo

Boiling of a liquid subcooled relative to its saturation temperature is a process that provides the most intense apparatuses cooling. Corresponding equipment designing is based on purely empirical correlations. Development of a theory and methods of mathematical description of the process is restrained by a limited experimental data base, first of all, on boiling characteristics. These characteristics are usually obtained as a result of statistical generalization of the data of high-speed filming of the process. However, reliable filming can be realized only at small and moderate heat flux densities, when neighboring bubbles do not shadow each other. More wide range of heat fluxes and other important parameters can be embraced while studying an evolution of a solitary bubble.

To solve this problem, an experimental installation was constructed for studying subcooled water boiling at a small-area spot of 1-3 mm diameter under forced convection conditions. Heat transfer surface was heated by a focused laser beam, its temperature was measured by a thermovisor, and high-speed camera provided boiling process visualization with a frequency up to 100 kHz. The experiments were conducted at smooth stainless and aluminum surfaces with Al2O3 coating formed using micro-arc oxidation technology. Data on a frequency of the solitary bubble origination, duration of the phases of the bubble life, bubble size and shape evolution were obtained.

Comparison of the bubble characteristics obtained from an analysis of the solitary bubble behavior with those taken from statistical treatment of the bubble multitude formed at the extended heating surface revealed their good correspondence. Thus, a conclusion can be made that the data obtained for the solitary bubble, apparently, can be spread to the actual boiling case at extended surfaces. Such a fact expands the possibilities of the process simulating.