Numerical simulation of forced and mixed convection turbulent liquid sodium flow over a vertical backward facing step with a four parameter turbulence model

During the working period of decay heat removal system, the flow rate of liquid sodium in wire-wrapped fuel assembly is very low, generally Re < 1000 . In the present study, both experimental methods and numerical simulation methods are applied. First, water experiment of 37-pin wire-wrapped rod bundle was carried out. Then, the numerical simulation study was carried out, the experimental data and the numerical simulation results were compared and analyzed, and a suitable turbulence model was selected to simulate the liquid sodium medium. Finally, numerical simulations under different boundary conditions were performed. Results indicate that except for the low Reynolds number k - ε turbulence model, other turbulence models have little difference with the experimental results. The results of realizable k - ε turbulence model are the most close to the experimental results. Compared with the friction factor obtained by using water medium and liquid sodium medium, the calculation results of water medium and sodium medium under the same condition are basically consistent, with the deviation within 1%. The reason is that the velocity of water is higher than sodium medium at the same Reynolds number, and the transverse disturbance caused by helical wire is larger.

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MIXED CONVECTION OF NANOFLUID OVER A BACKWARD FACING STEP UNDER THE EFFECTS OF A TRIANGULAR OBSTACLE AND INCLINED MAGNETIC FIELD

Computational Thermal Sciences An International Journal ◽

10.1615/computthermalscien.2018020085 ◽

2018 ◽

Vol 10 (6) ◽

pp. 521-543

Author(s):

Fatih Selimefendigil ◽

Hakan F. Öztop

Keyword(s):

Magnetic Field ◽

Mixed Convection ◽

Inclined Magnetic Field ◽

Backward Facing Step

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Modeling of mass transfer in biofilms in oscillatory flow conditions using k-ɛ turbulence model

Water Science & Technology Water Supply ◽

10.2166/ws.2003.0104 ◽

2003 ◽

Vol 3 (1-2) ◽

pp. 201-207

Author(s):

H. Nagaoka ◽

T. Nakano ◽

D. Akimoto

Keyword(s):

Numerical Simulation ◽

Mass Transfer ◽

Turbulence Model ◽

Uptake Rate ◽

Oscillatory Flow ◽

Substrate Uptake ◽

Flow Conditions ◽

Mass Transfer Mechanism ◽

Substrate Uptake Rate ◽

Good Agreement

The objective of this research is to investigate mass transfer mechanism in biofilms under oscillatory flow conditions. Numerical simulation of turbulence near a biofilm was conducted using the low Reynold’s number k-ɛ turbulence model. Substrate transfer in biofilms under oscillatory flow conditions was assumed to be carried out by turbulent diffusion caused by fluid movement and substrate concentration profile in biofilm was calculated. An experiment was carried out to measure velocity profile near a biofilm under oscillatory flow conditions and the influence of the turbulence on substrate uptake rate by the biofilm was also measured. Measured turbulence was in good agreement with the calculated one and the influence of the turbulence on the substrate uptake rate was well explained by the simulation.

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Uncertainties Analysis on the Prediction of Flow and Heat Transfer of Liquid Sodium with CFD Technology

Science and Technology of Nuclear Installations ◽

10.1155/2020/4239143 ◽

2020 ◽

Vol 2020 ◽

pp. 1-13

Author(s):

Zhanwei Liu ◽

Xinyu Li ◽

Tenglong Cong ◽

Rui Zhang ◽

Lingyun Zheng ◽

...

Keyword(s):

Heat Transfer ◽

Nusselt Number ◽

Friction Coefficient ◽

Liquid Sodium ◽

Heat Transfer Characteristics ◽

Backward Facing Step ◽

Heating Wall ◽

Transfer Characteristics ◽

Cfd Models ◽

Flow And Heat Transfer

The prediction of flow and heat transfer characteristics of liquid sodium with CFD technology is of significant importance for the design and safety analysis of sodium-cooled fast reactor. The accuracies and uncertainties of the CFD models should be evaluated to improve the confidence of the numerical results. In this work, the uncertainties from the turbulent model, boundary conditions, and physical properties for the flow and heat transfer of liquid sodium were evaluated against the experimental data. The results of uncertainty quantization show that the maximum uncertainties of the Nusselt number and friction coefficient occurred in the transition zone from the inlet to the fully developed region in the circular tube, while they occurred near the reattachment point in the backward-facing step. Furthermore, in backward-facing step flow, the maximum uncertainty of temperature migrated from the heating wall to the geometric center of the channel, while the maximum uncertainty of velocity occurred near the vortex zone. The results of sensitivity analysis illustrate that the Nusselt number was negatively correlated with the thermal conductivity and turbulent Prandtl number, while the friction coefficient was positively correlated with the density and Von Karman constant. This work can be a reference to evaluate the accuracy of the standard k-ε model in predicting the flow and heat transfer characteristics of liquid sodium.

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