TY - JFULL AU - Eggertson and E.C. Kapulla and R and Fokken and J and Prasser and H.M. PY - 2011/5/ TI - Turbulent Mixing and its Effects on Thermal Fatigue in Nuclear Reactors T2 - International Journal of Physical and Mathematical Sciences SP - 527 EP - 535 VL - 5 SN - 1307-6892 UR - https://publications.waset.org/pdf/4949 PU - World Academy of Science, Engineering and Technology NX - Open Science Index 52, 2011 N2 - The turbulent mixing of coolant streams of different temperature and density can cause severe temperature fluctuations in piping systems in nuclear reactors. In certain periodic contraction cycles these conditions lead to thermal fatigue. The resulting aging effect prompts investigation in how the mixing of flows over a sharp temperature/density interface evolves. To study the fundamental turbulent mixing phenomena in the presence of density gradients, isokinetic (shear-free) mixing experiments are performed in a square channel with Reynolds numbers ranging from 2-500 to 60-000. Sucrose is used to create the density difference. A Wire Mesh Sensor (WMS) is used to determine the concentration map of the flow in the cross section. The mean interface width as a function of velocity, density difference and distance from the mixing point are analyzed based on traditional methods chosen for the purposes of atmospheric/oceanic stratification analyses. A definition of the mixing layer thickness more appropriate to thermal fatigue and based on mixedness is devised. This definition shows that the thermal fatigue risk assessed using simple mixing layer growth can be misleading and why an approach that separates the effects of large scale (turbulent) and small scale (molecular) mixing is necessary. ER -