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NEW WALL DRAG AND FORM LOSS MODELS FOR ONE-DIMENSIONAL DISPERSED TWO-PHASE FLOW
김병재,이성욱,김경두 한국원자력학회 2015 Nuclear Engineering and Technology Vol.47 No.4
It had been disputed how to apply wall drag to the dispersed phase in the framework of theconventional two-fluid model for two-phase flows. Recently, Kim et al. [1] introduced thevolume-averaged momentum equation based on the equation of a solid/fluid particlemotion. They showed theoretically that for dispersed two-phase flows, the overall twophasepressure drop by wall friction must be apportioned to each phase, in proportion toeach phase fraction. In this study, the validity of the proposed wall drag model isdemonstrated though one-dimensional (1D) simulations. In addition, it is shown that theexisting form loss model incorrectly predicts the motion of the dispersed phase. A newform loss model is proposed to overcome that problem. The newly proposed form lossmodel is tested in the region covering the lower plenum and the core in a nuclear powerplant. As a result, it is shown that the new models can correctly predict the relative velocityof the dispersed phase to the surrounding fluid velocity in the core with spacer grids.
Two-fluid equations for two-phase flows in moving systems
김병재,김명호,이승욱,김경두 한국원자력학회 2019 Nuclear Engineering and Technology Vol.51 No.6
Recently, ocean nuclear reactors have received attention due to enhanced safety features. The movableand transportable characteristics distinguish ocean nuclear reactors from land-based nuclear reactors. Therefore, for safety/design analysis of the ocean reactor, the thermos-hydraulics must be investigated inthe moving system. However, there are no studies reporting the general two-fluid equations that can beused for multi-dimensional simulations of two-phase flows in moving systems. This study is to systematicallyformulate the multi-dimensional two-fluid equations in the non-inertial frame of reference. To demonstrate the applicability of the formulated equations, we perform a total of six different simulationsin 2D tanks with translational and/or rotational motions.