Visualization Experiment And Application Of Gas-liquid Two-phase Header Flow Distribution

The gas-liquid two-phase flow distribution phenomenon in multi-parallel branch pipe headers is common in some industrial heat exchange equipments.The uniformity of the distribution directly affects the safety and economy of the heat exchange equipment operation.Compared with single-phase flow,two-phase flow are much more complicated in terms of flow mechanism and heat transfer performance,and uneven flow distribution often occurs.Therefore,it is very important to study the flow and distribution characteristics of two-phase flow in manifold.In this paper,the single-entry horizontal radial introduction of the header is the research object,and the flow distribution in different header structures under the laminar flow and wavy flow is studied experimentally.By observing the flow ratio distribution in each branch pipe,it can be found that the addition of the flute pipe can greatly improve the distribution in the header,especially in the wavy flow pattern.At the same time,with the help of high-speed photography,the static and dynamic visual analysis of the two-phase flow distribution of the experimental platform is carried out.It is found that there is an obvious secondary in the header after the installation of the flute tube.During the distribution process,the stratification of gas-liquid two phases disappears.After the two-phase flow is throttled and accelerated by the flute-shaped holes,it is vigorously mixed in the annular cavity and leaves the header.The existence of the flute tube weakens the uneven distribution of the two-phase fluid in the axial direction,and the distribution in each branch tube is better.The geometric structure has a good distribution effect on various two-phase flow patterns.For the long-term low load(180MW,30%BMCR)flexible operation of a 600MW supercritical unit,the over-temperature phenomenon of the vertical pipe water wall is analyzed.The data shows that the temperature difference between two adjacent tubes can reach 130℃,which seriously affects the safe operation of the unit.Through the trend of wall temperature,the cause of this phenomenon is analyzed and verified by modeling experiments.Based on the research results,the control measures of over-temperature problem under low-load flexible operation are proposed.