Boiling flow visualization experiment scaled to divertor cooling conditions

Gajšek, Aljoša (author), Kozmus, Gregor (author), Tekavčič, Matej (author), Richou, Marianne (author), Končar, Boštjan (author)

A dedicated experiment FEDORA (Fusion Experiment for Divertor Optimization Research Applications) has been constructed to visualize flow boiling at scaled fusion divertor conditions. Its main purpose is to obtain the information on local boiling parameters, needed for the development of mechanistic boiling models in Computational Fluid Dynamics (CFD) codes. Current boiling models, although grounded on realistic physical principles, still rely heavily on empirical correlations, particularly for boiling parameters such as nucleation site density, bubble departure diameter, and bubble departure frequency. Due to the harsh operating conditions in the water-cooled divertor plasma-facing components (high heat fluxes over 10 MW/m$^2$, mean flow velocity of about 9 m/s), visualization of boiling in realistic cooling channels is not feasible. The proposed experiment addresses this challenge by employing a surrogate coolant, characterized by lower latent heat and saturation temperature. By analyzing key dimensionless numbers, the aim is to replicate boiling conditions to be similar to those in coolant channels of upcoming divertor designs. Distinctive features of the proposed experimental setup include visually transparent boiling channel, infra-red transparent window and a thin electrically heated foil. This setup allows simultaneous high-speed and high-resolution recording of boiling phenomena in the flow and measurement of temperature distribution on the heated surface. In this work, the design, similarity analysis and the first measurement results are presented, proving the concept of the visualization approach to understand the boiling heat transfer in divertor cooling channels.

• Language: English
• Keywords: flow boiling, high-heat flux, divertor cooling conditions, visualization experiment, boiling parameters
• Work type: Article
• Typology: 1.01 - Original Scientific Article
• Organization: FMF - Faculty of Mathematics and Physics
• Publication status: Published
• Publication version: Version of Record
• Year: 2025
• Number of pages: 6 str.
• Numbering: Vol. 218, art. 115188
• PID: 20.500.12556/RUL-181982
• UDC: 621.039
• ISSN on article: 0920-3796
• DOI: 10.1016/j.fusengdes.2025.115188
• COBISS.SI-ID: 238773251
• Publication date in RUL: 21.04.2026

Record is a part of a journal

• Title: Fusion engineering and design
• Shortened title: Fusion eng. des.
• Publisher: Elsevier
• ISSN: 0920-3796
• COBISS.SI-ID: 15359237

Licences

• License: CC BY-NC 4.0, Creative Commons Attribution-NonCommercial 4.0 International
• Link: http://creativecommons.org/licenses/by-nc/4.0/
• Description: A creative commons license that bans commercial use, but the users don’t have to license their derivative works on the same terms.

Secondary language

• Language: Slovenian
• Keywords: jedrska tehnika, vrenje, pretok