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Turbulence Heat and Mass Transfer 6. Proceedings of the Sixth International Symposium On Turbulence Heat and Mass Transfer
September, 14-18, 2009, Rome, Italy

DOI: 10.1615/ICHMT.2009.TurbulHeatMassTransf


ISBN Print: 978-1-56700-262-1

ISSN: 2377-2816

Experimental and Numerical Mixing Studies Relevant for Prediction of Thermal Loads in T-junctions

page 12
DOI: 10.1615/ICHMT.2009.TurbulHeatMassTransf.1050
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RÉSUMÉ

As nuclear plants age and as it is generally desirable to extend their life-time, the issue of fatigue associated with cyclic thermal loads becomes increasingly important. Cyclic thermal loads can occur in different parts of a plant and are invariantly associated with mixing of streams at different temperatures occurring at characteristic frequency and over a sufficient number of cycles. A prominent example of such a mixing occurs in T-junctions where hot and cold streams are not yet completely mixed. In this work we report on the measurement techniques used to study mixing processes in T-junctions and associated numerical investigations. The measurement technique is based on high-frequency wire-mesh sensor (WMS) which measures electrical conductivities of two water streams mixing at the junction: normal (conductive) water in the main branch mixes with desalinated (non-conductive) water from the side branch. Although the measurements are performed adiabatically, the analogy between the scalar equations for species and enthalpy transport gives us insight on mixing of streams at different temperatures. Numerical analysis is based on large eddy simulations (LES) of turbulence, and is performed with commercial computational fluid dynamics (CFD) package FLUENT. Results obtained with LES compare very well with measurements, showing the potential to estimate thermal fluctuations in T-junctions for sub-sequent fatigue analysis.

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