6533b839fe1ef96bd12a5f9f

RESEARCH PRODUCT

CFD predictions of turbulent two-phase flow in helical coils

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Turbulent two-phase flow in a helical pipe was simulated by means of CFD using the ANSYS-CFX code, based on a finite-volume multi-fluid approach. The focus was on flow patterns and frictional pressure drops; inter-phase heat and mass transfer and heat exchange with the pipe walls were not included and physical properties were assumed constant for each phase. The computational domain included a single, vertical axis, coil turn; the flow was assumed to be fully developed. Geometry and physical conditions were representative of the IRIS nuclear reactor steam generators (saturated water at 58 bar, pressure gradient of 0.1 bar/m). Void fraction and computational options (homogeneous vs. inhomogeneous two-phase model, homogeneous vs. phase-specific k- and k- turbulence models, interphase drag model parameters, grid, steady-state vs. transient approach) were made to vary in a sensitivity analysis. Literature correlations were used as reference. Using the inhomogeneous two-phase model, results exhibited a sharp liquid-gas interface; the light (gas) and heavy (liquid) phases stratified diagonally in the cross section under the combined action of gravity and centrifugal forces. Inter-phase drag parameters had only a minor influence on the results. The homogeneous model yielded a uniform mixture at all values of . With all options, the simulations overestimated the mass flow rate for imposed pressure drop and quality. Only minor differences in the results were obtained by changing the turbulence model. Even less was the influence of grid size and other computational details. The influence of gravity was small but not negligible under the conditions investigated.