Prediction of Dryout and Post Dryout Behaviour of Clad Surface During Flow of Water over a Vertical Heated Rod

ABSTRACT

Critical heat flux (CHF) is an important parameter for the design and operation of nuclear reactors and in many boiling heat exchangers. Critical heat flux occurs by two mechanisms viz departure from nucleate boiling and annular film dry out. CHF is traditionally evaluated using look up tables or empirical correlations. A model of annular two phase flow is being used here to calculate dryout assuming that dry out occurs when the liquid flow rate in the film formed on the solid surfaces becomes zero. Another important parameter is the clad surface temperature, which needs to be predicted accurately for nuclear reactor safety. Accurate prediction of clad surface temperature requires correct prediction of critical heat flux. In the present paper, the mathematical models for CHF and clad surface temperature have been developed and solved.

Keywords: Two phase flow, Critical heat flux

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