An image processing technique for the study of vapor film dynamics during quenching of a downward facing hemisphere

Faith R. Beck, Nurali Virani, Lokanath Mohanta, Faruk A. Sohag, Asok Ray, Fan Bill Cheung

Research output: Contribution to conferencePaper

3 Scopus citations

Abstract

Understanding two-phase heat transfer mechanisms on downward facing hemispherical vessels is crucial during external reactor vessel cooling (ERVC) under severe accident conditions. Film boiling could be the predominant heat transfer regime in the initial stages of quenching under these circumstances. In this work, the process of downward facing film boiling on the outer surface of a hemispherical vessel is studied using high-speed photography. This technique does not require any invasive sensors, which may alter the natural liquid-vapor interface in film boiling. Using a high-speed camera and several image processing techniques, more accurate measurements of film thickness have been made at different degrees of subcooling (0°C, 3°C, 5°C, and 10°C) and several angular locations (0°, 14°, 28°, and 42°) on a hemispherical vessel. With increased liquid subcooling and decreasing angular locations, the vapor film thickness has been found to decrease. Average film thicknesses at 0°C subcooling (resp. 5°C), one second after immersion were found to be approximately 2 mm (resp. 0.5 mm). High-speed videos (with frame rates as high as 650 fps) have shown significant oscillations at the liquid-vapor interface during film boiling. Additionally, oscillations in the film thickness and its wave characteristics have been analyzed at the prescribed angular locations and degrees of subcooling. From the visual data, insights can be made regarding the heat transfer behavior of film boiling; an attempt has been made to qualitatively relate the characteristics of oscillation waves to the vessel temperature.

Original languageEnglish (US)
StatePublished - Jan 1 2017
Event17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017 - Xi'an, Shaanxi, China
Duration: Sep 3 2017Sep 8 2017

Other

Other17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017
CountryChina
CityXi'an, Shaanxi
Period9/3/179/8/17

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All Science Journal Classification (ASJC) codes

  • Nuclear Energy and Engineering
  • Instrumentation

Cite this

Beck, F. R., Virani, N., Mohanta, L., Sohag, F. A., Ray, A., & Cheung, F. B. (2017). An image processing technique for the study of vapor film dynamics during quenching of a downward facing hemisphere. Paper presented at 17th International Topical Meeting on Nuclear Reactor Thermal Hydraulics, NURETH 2017, Xi'an, Shaanxi, China.