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Turbulent Penetration as a Thermal Fatigue Problem in low Side Flow T-Junctions

Type of publication Peer-reviewed
Publikationsform Proceedings (peer-reviewed)
Publication date 2012
Author Kickhofel John, Valori valentina, Prasser Horst Michael,
Project Temperature Fluctuations in Fluid and Pipe Walls induced by Turbulent Mixing
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Proceedings (peer-reviewed)

Title of proceedings Nuclear Thermal Hydraulics and Safety 8 (NTHAS8)
Place Beppu, Japan

Abstract

The Laboratory for Nuclear Energy Systems (LKE) at the ETH Zürich in Switzerland introduces a new T-junction facility designed and built expressly for the purpose of studying turbulent penetration mixing in the context of the thermal fatigue problem in nuclear power plant piping. The working fluid is water at 20°C, with the electrical conductivity of the fluid as an analogy to temperature, in a T-junction with a branch diameter ratio of 1 (D = 50 mm). The fluid mixing, in which turbulence in the main branch intermittently forces its way into the weak side branch flow, is dominated by high frequency scalar fluctuations in the mixing branch and low frequency fluctuations in the side branch. Wire mesh sensors measure the conductivity with high time (2500 Hz) and spatial (1.5 mm) resolution over the entire pipe cross section. The test matrix includes low side/main branch velocity ratios (<= 0.035) with wire mesh sensors positioned in the mixing branch at x/D = 1 and in the side branch at varying y/D from 1 to 4. Zones of high scalar fluctuations are found to vary not only in position along the axis of the side branch but also around the perimeter of the side branch.
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