Study On Flow Regime Of Gas-liquid Two-phase Flow In In-line And Staggered Tube Bundle Arrays

The flow phenomenon of multiphase flow is widespread,and its flow structure is an important factor determining the overall performance of the heat exchanger.Concentrated porosity can lead to poor heat transfer and even pipe failure due to localized drying.Therefore,it is very important to study the flow structure of the two-phase flow in the tube bundle,which is helpful to understand and predict the effect of different flow conditions on the performance of heat exchange equipment.In this paper,the gas-liquid two-phase flow laterally scours the in-line and staggered tube bundles in the vertical direction,and the flow characteristics and flow pattern conversion rules of the bubble flow and intermittent flow in the surrounding flow field are studied in detail.Numerical simulation was carried out using OpenFOAM’s multiphaseEulerFoam solver combined with large eddy simulation.For the in-line and staggered tube bundles of gas-liquid two-phase flow,a quantitative assumption scheme of the experiment is firstly proposed,which is convenient for numerical analysis.The inflow porosity is controlled at a low value(α<0.05)as a fixed value.At this time,the two-phase flow is in the state of bubbly flow.With the increase of the inflow velocity,it is observed that the gas phase distribution in the basin presents a regular change.The position of the bubble distribution is closely related to the inflow velocity;at the same time,it is found that the velocity distribution of the gas phase and the liquid phase is very different,and the slip ratio of the two-phase velocity decreases with the increase of the flow rate;the gas phase is in the form of dispersed bubbles in this flow state flow with the liquid.In order to realize the numerical calculation of flow pattern transition from bubble flow to intermittent flow,a second quantitative assumption scheme is proposed.For the case of high inflow porosity(0.1<α<0.7),keeping the inflow velocity constant and increasing the inflow porosity continuously,the transition process of the two-phase flow to the intermittent flow pattern can be observed.The gas in the surrounding flow field under the intermittent flow pattern exists in the form of separated large-diameter bubbles or air masses,and the diameter of the air masses can even exceed 1 to 2 times the diameter of the cylindrical tube bundle.The gas phase is separated from the liquid,and the liquid phase is separated.It is divided into incomplete continuous liquid masses,and the flow is unstable under this flow state,with strong flow pulsation.In addition,this paper also studies the effect of bubble diameter on the flow regime of two-phase flow.The size of the average diameter of the bubbles will affect the distribution of the void fraction,resulting in a change in the velocity-slip ratio of the gas-liquid two-phase.Different bubbles have different average diameters,and the lateral movement ability of bubbles is also different.In this paper,the porosity distribution and the two-phase velocity distribution are also studied when the two-phase flow rotates around the triangular array and the rotating quadrilateral array.