The actual redesign of the Mark A top plug to minimize heat convection, by using piston rings in the vertical annuli and neglecting all thermal resistance in the short sodium annuli thus formed, is conservative if the rings fit tight and effectively prevent vertical flow around themselves. However, due to uncertainties in correlation of the available data, it seems the best procedure for keep the heat transfer below a redid maximum.nLess conservative, but still somewhat conservative design with tight rings is obtained by using an overall heat transfer coefficient across each vertical annulus as given by the relation NuL = 3.
展开▼
