Basic laws and coolability of particulate debris: comments on the status and present contributions

As already indicated by the contributions in Part 1 of this issue, an enhanced coolability can be expected especially from multi-dimensional coolant flows in non-uniform particle beds, compared with earlier analyses based on one-dimensional configurations under top flooding and related dryout heat fluxes (DHF). However, assured basic local laws of friction and heat transfer in such beds are required to really evaluate the coolability potential with multidimensional computer codes. Thus, as a common subject, this part of the present issue refers to experimental investigations and related modelling on basic laws of friction and heat transfer in particle beds. Since such laws are often investigated mainly with respect to dryout phenomena (“dryout heat flux”: DHF) this connection is also addressed here. A general impression is that the approaches are widely spread, as concerns the specific experimental aims and methods, the range of conditions analysed, the phenomena emphasised, the empirical laws derived and the conclusions indicated for coolability, especially under reactor conditions. Thus, it appears to be important to confront these approaches with one another in order to find a common line of major subjects and of derivation or validation of relevant empirical laws. Certainly, this cannot be finally reached here and by the present issue. A first step is undertaken here, trying to discuss remaining problems and tasks for future work.