CFD simulation of a bubbly flow experiment with liquid PbBi eutectic alloy and Nitrogen


CFD simulation of a bubbly flow experiment with liquid PbBi eutectic alloy and Nitrogen

Mercurio, G.; Eckert, S.

This study was carried out in the frame of the ADS European project aimed to the development of Accelerator Driven System technology for nuclear waste transmutation.
The scope is to verify the possibility to simulate a two phase HLM (Heavy Liquid Metal) bubbly flow using the commercial CFD code CFX4.4.
The first stage consisted of an experimental campaign for the measurement of the phase velocities by means of the ultrasound Doppler velocimetry (UDV) and local volume fractions using resistive probes. The eutectic alloy PbBi is located inside a cylindrical container made of stainless steel which is provided with an electrical heater. The measurements reported here were carried out at a fluid temperature of 180°C. Nitrogen (N2) gas was injected into the stagnant liquid metal by means of a single orifice with an inner diameter of 0.5 mm. The orifice is located in the centre of the cross-sectional area of the fluid container. The gas flow rate chosen for these experiments was restricted to values below 1.2 cm3/s in order to guarantee a single bubble flow regime.
The simulation of the experiment was performed using the two fluid Euler/Euler model of CFX-4.4. The implemented drag laws were tested and compared with other drag laws taken from literature. The influence of the "non-drag forces" like the turbulent dispersion force and the lift force was also tested. Finally an advanced interpolation method based on optimization techniques was adopted in order to get the best fitting of the simulated velocity curves with the experimental ones. The results shows in general a good qualitative agreement of the experiment and the calculations, but a much better agreement can be found using the drag law coefficients derived by the above mentioned optimization technique, especially in the cases where the mass flow rates and the bubble mean diameters are relatively small.

Keywords: two-phase flow; gas bubbles; heavy liquid metals; drag force; velocity measurements; UDV technique

  • Lecture (Conference)
    Computational Methods in Multiphase Flow II, A.A.Mammoli, C.A.Brebbia (Eds.), WIT Press 2004, Southampton pp.395-404, (Proc. of the Second International Conference on Computational Methods in Multiphase Flow, Santa Fe, New Mexico, USA, 2003)
  • Contribution to proceedings
    Computational Methods in Multiphase Flow II, A.A.Mammoli, C.A.Brebbia (Eds.), WIT Press 2004, Southampton pp.395-404, (Proc. of the Second International Conference on Computational Methods in Multiphase Flow, Santa Fe, New Mexico, USA, 2003)

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