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ISSN Online: 2377-424X

ISBN Print: 978-1-56700-474-8

ISBN Online: 978-1-56700-473-1

International Heat Transfer Conference 16
August, 10-15, 2018, Beijing, China

NUMERICAL STUDY OF THE MIXING OF STEAM AND AIR IN A FUEL ASSEMBLY IN CROSS-FLOW

Get access (open in a dialog) DOI: 10.1615/IHTC16.nee.022377
pages 7804-7811

摘要

Buoyancy-affected heat and mass transfer in a fuel assembly after a loss-of-cooling accident is investigated. Under these conditions, natural convection of air in the containment has an impact on cooling of the fuel assemblies. This large-scale convection causes a persistent horizontal flow above the fuel assemblies. To investigate the influence of horizontal cross-flow on mixing and temperature distribution, a three-dimensional CFD analysis is performed. The numerical setup consists of a square T-junction, where the upper part of a pressurized water reactor fuel assembly is located in the vertical branch section and air flows horizontally in the main section. Two expectable scenarios are examined using different fluid combinations in main and branch section. The complete drainage scenario is covered by an air/air case, the partial drainage scenario is covered by an air/steam case. Temperatures and velocities in branch and main section are set to cover a broad range of potential states in an evaporating spent fuel pool. Flow patterns depend on two dimensionless quantities: momentum flux ratio and Richardson number. A parameter variation of these numbers reveals their influence on mixing intensity and intrusion length. Maximum values are observed at high Richardson numbers and low momentum flux ratios. Results indicate that Richardson number is the dominant of both quantities. The study shows that intrusion of air into the fuel assembly is possible even under moderate conditions thereby making a significant contribution to cooling.