COSMOS-L: Flow during Critical Heat Flux

Video of flow boiling under forced convection in an annular gap during the appearance of the Critical Heat Flux (CHF). The measuring position is in a distance of 306 mm of the inlet into the annulus. The total heated langth is about 326 mm. CHF always applied at the top end close to the displayed video position.
On the one hand, the flow is shown for about 45 seconds before CHF applied and on the other hand 30-45 seconds after CHF was reached. Directly after detecting the CHF (temperature rise), the heating power was shut off. The temporal appearance of the CHF is marked in the video.
The flow direction is vertical from bottom to top. Deionized water is used as test medium. The CHF occurs as departure from nucleate boiling (DNB). At the end of each video the boundary conditions are described. The presented video is visualized with 25 fps.
The following overview shows the measuring points and recorded framerates in the video:
- T80G400P2000 (3.000 frames per second)
- T80G600P2000 (3.000 fps - starting at 2:00)
- T65G400P2000 (3.000 fps - starting at 3:45)
- T80G400P1200 (4.000 fps - starting at 5:30)

The whole series was recorded on the test facility COSMOS-L of the Institute for Thermal Energy Technology and Safety (ITES).
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Further information is available under:
http://www.ites.kit.edu/128.php

Acknowledgements:
We would like to thank Prof. Dr.-Ing. T. Wetzel (TVT) for his expert advices and encouragement to publish this video series, as well as to G. Albrecht (ITES) and W. Heiler (ProScience GmbH) for their brilliance in the lab and wonderful collaboration during the whole project.
The authors are grateful for the financial support by the Federal Ministry for Economic Affairs and
Energy (BMWi), who fund this research under the funding code 1501473B.