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Numerical and Experimental Simulation of the Thermal Stratification in a Horizontal Pipe
Moysés Alberto Navarro, Hugo Cesar Rezende, André Augusto Campagnole Dos Santos and Hermes Carvalho

Stratified flows causes thermal loading and fatigue relevant stresses in piping systems. It can occur due to the density difference between two layers of the same liquid at different temperatures and flowing separately in horizontal pipes without appreciable mixing. The temperature gradient from top to bottom in the pipe cross section may result in excessive differential expansion from upper to lower parts of the pipe threatening its integrity. This paper reports a thermal-hydraulic assessment of stratified flow, under conditions similar to the steam generator injection nozzle of a pressurized water reactor. Numerical results obtained with a commercial finite volume CFD code CFX-10.0 are presented and compared with experimental data. Both results confirmed the occurrence of thermal stratification under simulated conditions.

Keywords: Thermal Stratification, Striping, CFD, Turbulence Model, Steam Generator, Nuclear Safety, PWR.

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