It is shown that, using a single volume to lump the heat source and sink, it was not possible to reach convergence to steady state flow rate when the heated (cooled) length was diminished and the heat transfer coefficient increased to keep constant the total heat transferred to (and removed from) the fluid. An algebraic justification of these results is presented. Concerning the effect of nodalization on the damping of instabilities, it was shown that 'reasonably fine' discretization lead to damping. However, the search for convergence of numerical and theoretical results was successful, showing the expected nearly chaotic behaviour. This search lead to very refined nodalization. The results obtained have also been verified by the use of simple, ad hoc codes.
On the convergence of RELAP5 calculations in a single-phase natural circulation problem
AMBROSINI, WALTER;D'AURIA, FRANCESCO SAVERIO
1995-01-01
Abstract
It is shown that, using a single volume to lump the heat source and sink, it was not possible to reach convergence to steady state flow rate when the heated (cooled) length was diminished and the heat transfer coefficient increased to keep constant the total heat transferred to (and removed from) the fluid. An algebraic justification of these results is presented. Concerning the effect of nodalization on the damping of instabilities, it was shown that 'reasonably fine' discretization lead to damping. However, the search for convergence of numerical and theoretical results was successful, showing the expected nearly chaotic behaviour. This search lead to very refined nodalization. The results obtained have also been verified by the use of simple, ad hoc codes.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
