Heat transfer from saturated and superheated atmospheres for containment analysis

Abstract

Heat transfer correlations used in containment analysis are reviewed. Particular attention is paid to the Main Steam Line Break (MSLB) accident, which can lead to superheated atmospheres. It is shown that the standard condensating heat transfer correlations are inapplicable for such conditions. A new condensing-convective heat transfer model is derived on the basis of a mechanistic analysis of a vapour-steam boundary layer on a vertical condensing surface. The expression is normalized to experimental data in order to include the effect of forced convection. The new correlation is applicable to the superheated and saturated state and provides a smooth transition between both heat transfer regimes. It evaluates implicitly both condensing and convective heat transfer as a function of atmospheric and wall temperature conditions, and thus determines not only the total amount of heat transferred but also the amount of condensate formed.