Calculation of dryout and post-dryout heat transfer for tube geometry

A method for calculating dryout power and post-dryout heat transfer in tube geometry is described and validation results are presented. A two-phase, three-field annular flow model is utilized, which bases dryout on the criterion of a disappearing liquid film at the wall. Entrainment and deposition are key phenomena and have to be adequately modelled, including the effect of wall heat flux. The calculational method is tested in the framework of the MONA code and validated against the KTH dryout experiments. The model generally provides good results for dryout position and power, and successfully takes account of variations in tube diameter, pressure, and mass and heat flux. The model predicts the effect of a varying axial heat flux distribution especially well, as mechanisms like heat flux induced entrainment and deposition inhibition through film evaporation are accounted for. Also post-dryout heat transfer predictions agree well with little systematic deviation and correct shapes of the temperature profiles.

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