 |
Journal articles
Criticality in the slowed-down boiling crisis at zero gravity
Abstract : Boiling crisis is a transition between nucleate and film boiling. It occurs at a threshold value of the heat flux from the heater called CHF (critical heat flux). Usually, boiling crisis studies are hindered by the high CHF and short transition duration (below 1 ms). Here we report on experiments in hydrogen near its liquid-vapor critical point, in which the CHF is low and the dynamics slow enough to be resolved. As under such conditions the surface tension is very small, the experiments are carried out in the reduced gravity to preserve the conventional bubble geometry. Weightlessness is created artificially in two-phase hydrogen by compensating gravity with magnetic forces. We were able to reveal the fractal structure of the contour of the percolating cluster of the dry areas at the heater that precedes the boiling crisis. We provide a direct statistical analysis of dry spot areas that confirms the boiling crisis at zero gravity as a scale-free phenomenon. It was observed that, in agreement with theoretical predictions, saturated boiling CHF tends to zero (within the precision of our thermal control system) in zero gravity, which suggests that the boiling crisis may be observed at any heat flux provided the experiment lasts long enough.
Cited literature [36 references]
https://hal-cea.archives-ouvertes.fr/cea-01366768
Contributor : Dominique Girard <>
Submitted on : Thursday, September 15, 2016 - 12:13:03 PM
Last modification on : Tuesday, December 8, 2020 - 11:02:13 AM
Long-term archiving on: : Friday, December 16, 2016 - 2:05:10 PM
Contributor : Dominique Girard <>
Submitted on : Thursday, September 15, 2016 - 12:13:03 PM
Last modification on : Tuesday, December 8, 2020 - 11:02:13 AM
Long-term archiving on: : Friday, December 16, 2016 - 2:05:10 PM
File
CLCTVBN_PRE_2015.pdf
Files produced by the author(s)