Heat Flux Partition based on Onset of Significant Void
Résumé
The thermal log-law is valid in flow boiling with a value of the additive constant that evolves as the flow develops. Using a multiphase flow cross-literature database, this constant is shown to be -7 at the point of onset of significant void (OSV). This means that at the OSV the liquid is at saturation temperature up to y+ = 30. The OSV predictions using this model have a similar mean average error as the Saha and Zuber 1974 correlation for one less fitted constant for channel, pipe and annular flows for pressure from 1 to 147bar and Peclet numbers from 3,500 to 400,000. This model is used to build a heat flux partitioning (HFP) inspired from system-scale codes. It predicts the distribution of the heat flux between the liquid phase and the evaporation term, and must be coupled with an empirical boiling total heat flux correlation to replace a traditional HFP. This partition provides more coherent flux distribution between the evaporation and liquid terms than Kurul and Podowski based approaches and improves void fraction predictions in high-subcooling regions on the DEBORA database and on experiments by Bartolomei et al.
Mots clés
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