Simulation of Two-phase Flow Pattern Transition in Helical Tubes With Variable Curvature
To further advance the performance of heat and mass transfer in the helical heat ex-change tubes of the steam generator,this paper presents an enhancement plan involving a helical tube design featuring periodic curvature changes.A numeric simulation study was conducted to examine the characteristics of a gas-liquid two-phase flow within tubes of varying curvature.By applying the finite element method,a hexahedral structured grid was established for the fluid flow within a single helical tube.The Volume of Fluid(VOF)model was utilized to capture the phase boundary,and the characteristics of the in-tube liquid phase flow field distribution were analyzed.The research found differing two-phase distributions and flow patterns in different sections within the same helically-curved tube,with some sections displaying an intermittent transition phenomenon from stratified flow to wavy flow,and then to plug flow.This phenomenon is attributed to the peri-odic variations in coil curvature,which in turn continuously alters the centrifugal force experienced by the in-tube liquid phase,leading to a dynamically changing two-phase distribution in both spatial and temporal contexts.
two-phase flowvariable curvature helical tubeflow pattern transitionsteam genera-torcentrifugal force
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