Basing on previous experience in assessing system codes and CFD mod- els in the prediction of heat transfer and flow stability with supercritical fluids, new steps of the research are presented in this paper. The new results are related to al- ready addressed heat transfer problems, revisited by a different computational tool, the commercial code STAR-CCM+, in front of available experimental data, and to multiple channel flow stability phenomena, as predicted by the RELAP5 code. After a short summary of the achievements obtained in previous phases of the research, recent re- sults are described, pointing out different aspects. In particular, the capability to predict heat transfer deterioration by the k-ε low-Re turbulent models available in STAR- CCM+ is assessed, with main emphasis on the presence of heat transfer deterioration in trans-pseudocritical conditions strongly affected by buoyancy; numerical aspects re- lated to the implementation of fluid thermodynamic and thermophysical properties in the CFD code are also addressed. Moreover, parallel channel instability phenomena are considered, as predicted by the RELAP5 code, describing the instability patterns obtained in slightly asymmetric channels and the observed numerical stabilising effects occurring in perfectly symmetric channels. Relevant conclusions and future perspec tives of the research are finally summarised.
Continuing Assessment of System and CFD Codes for Heat Transfer and Stability in Supercritical Fluids,
AMBROSINI, WALTER
2009-01-01
Abstract
Basing on previous experience in assessing system codes and CFD mod- els in the prediction of heat transfer and flow stability with supercritical fluids, new steps of the research are presented in this paper. The new results are related to al- ready addressed heat transfer problems, revisited by a different computational tool, the commercial code STAR-CCM+, in front of available experimental data, and to multiple channel flow stability phenomena, as predicted by the RELAP5 code. After a short summary of the achievements obtained in previous phases of the research, recent re- sults are described, pointing out different aspects. In particular, the capability to predict heat transfer deterioration by the k-ε low-Re turbulent models available in STAR- CCM+ is assessed, with main emphasis on the presence of heat transfer deterioration in trans-pseudocritical conditions strongly affected by buoyancy; numerical aspects re- lated to the implementation of fluid thermodynamic and thermophysical properties in the CFD code are also addressed. Moreover, parallel channel instability phenomena are considered, as predicted by the RELAP5 code, describing the instability patterns obtained in slightly asymmetric channels and the observed numerical stabilising effects occurring in perfectly symmetric channels. Relevant conclusions and future perspec tives of the research are finally summarised.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
