Thermal-hydraulics is recognized as a key (safety) challenge in the development of innovative nuclear reactor systems. Different innovative reactors are mainly characterized by their coolants from a thermal-hydraulic point of view. They result in different behavior of flow and heat transfer and require specific models and advanced analysis tools. However, many common thermal-hydraulic challenges are identified among various innovative nuclear systems. In Europe, such challenges are the subject of the THINS (Thermal-Hydraulics of Innovative Nuclear Systems) project which is sponsored by the European Commission from 2010 to 2014. This paper describes the ongoing developments in an important part of this project which is devoted to single phase turbulence issues. To this respect, two main issues have been identified: • Non-unity Prandtl number turbulence. In cases of liquid metals, molten salts or supercritical fluids, the commonly applied turbulent Prandtl number concept is not applicable and robust engineering turbulence models are needed. This paper will report about the experiments and direct numerical simulations which have been performed in support of validating improved turbulence models. Furthermore, this paper demonstrates the progress achieved in the development and validation of Reynolds Averaged Navier Stokes (RANS) and Large Eddy Simulation (LES) turbulence models. With respect to improved RANS models, carefully selected promising algebraic heat flux models have been implemented and evaluated which should lead to improved numerical modeling of non-unity Prandtl number flows. • Temperature fluctuations possibly leading to thermal fatigue in innovative reactors. A basic mixing experiment will be described of different density gases in a rectangular channel together with numerical model developments, support and validation. Secondly, the preparation of an experiment in a more complex geometry of a small mixing plenum using a supercritical fluid is described including the numerical support. And finally, direct numerical simulations of conjugate heat transfer on temperature fluctuations in liquid metal will be reported together with validation of LES models.

European Developments in Single Phase Turbulence for Innovative Reactors

AMBROSINI, WALTER;
2013

Abstract

Thermal-hydraulics is recognized as a key (safety) challenge in the development of innovative nuclear reactor systems. Different innovative reactors are mainly characterized by their coolants from a thermal-hydraulic point of view. They result in different behavior of flow and heat transfer and require specific models and advanced analysis tools. However, many common thermal-hydraulic challenges are identified among various innovative nuclear systems. In Europe, such challenges are the subject of the THINS (Thermal-Hydraulics of Innovative Nuclear Systems) project which is sponsored by the European Commission from 2010 to 2014. This paper describes the ongoing developments in an important part of this project which is devoted to single phase turbulence issues. To this respect, two main issues have been identified: • Non-unity Prandtl number turbulence. In cases of liquid metals, molten salts or supercritical fluids, the commonly applied turbulent Prandtl number concept is not applicable and robust engineering turbulence models are needed. This paper will report about the experiments and direct numerical simulations which have been performed in support of validating improved turbulence models. Furthermore, this paper demonstrates the progress achieved in the development and validation of Reynolds Averaged Navier Stokes (RANS) and Large Eddy Simulation (LES) turbulence models. With respect to improved RANS models, carefully selected promising algebraic heat flux models have been implemented and evaluated which should lead to improved numerical modeling of non-unity Prandtl number flows. • Temperature fluctuations possibly leading to thermal fatigue in innovative reactors. A basic mixing experiment will be described of different density gases in a rectangular channel together with numerical model developments, support and validation. Secondly, the preparation of an experiment in a more complex geometry of a small mixing plenum using a supercritical fluid is described including the numerical support. And finally, direct numerical simulations of conjugate heat transfer on temperature fluctuations in liquid metal will be reported together with validation of LES models.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/225560
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