多相流基础 chapter 2-two-phase flow patterns and flow pattern maps

（3）Stratified flow（光滑分层流）
Gas and liquid phase have obvious interface The gas-liquid interface is smooth This flow pattern does not usually occur Gas and liquid phase are both continuous phase
5、Flow patterns in vertical upward tubes ——gas and liquid phase both flowing upwards，heating up flow（垂直上升管内的流型 —— 气液两相均向上流 ，加热流）
Heat addition Phase change More complicated than adiabatic flow The evolvement of flow patterns are greatly affected by the heat flux（热流密度）
（2）Plug flow or Slug flow（弹状流） Gas flows as large bulletshaped bubbles（sometimes called Taylor bubble） Gas bubble and liquid slug flow across tube alternatively
Liquid is the continuous phase
Gas or vapor phase is the dispersed phase near the top of the tube
（2）Plug flow（塞状流、间歇流）
Bigger quality and low velocity Individual small gas bubbles coalesce to produce long plugs Gas bubbles still tend to flow along the top of the tube
Churn flow
Annular flow
—— The flow patterns of steam-water twophase flow in the tube when heat flux increases are as follows:
xx denotes ONB （onset of nuclear boiling） yy denotes onset of annular flow region zz denotes the point of CHF（ Critical heat flux ），it is a very dangerous point
Gas velocity is bigger than the stratified flow Gas and liquid phase are both continuous phase Gas phase flows above and liquid phase flows below
—— These names of flow pattern mentioned before are main flow patterns and relatively recognized accepted to us.
—— Further general details about flow patterns can be found in Collier and Thome(1994) and Hewitt(1982).
（1）Bubbly flow（泡状流）
Liquid phase is the continuous phase Gas or vapor phase is the dispersed phase Gas or vapor bubbles are of approximately uniform size.
Some small gas bubbles distributed throughout the liquid phase.
（3）Churn flow（搅拌流，块状流） Highly unstable flow， oscillatory flow the shape of gas bubbles is not regular Liquid near the tube wall continually pulses up and down
4、Flow patterns in horizontal tubes， adiabatic flow（水平管内两相流型，绝热流）
——When the quality is gradually increased from 0 to 1, the flow patterns can be classified: （1）Bubbly flow（泡状流） Low quality and low velocity
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Tip：the types of flow patterns increase in heating channel when heat flux increases.
6、Flow patterns in horizontal tubes， heating up flow（水平管内两相流型，加热流 ）
flow, but it has liquid film in plug flow.
（6）Annular flow（环状流）
Gas velocity is big enough Gas flows in the center of the tube Liquid partially flows as an annular film on the walls of the tube Liquid partially flows as small droplets distributed in the gas flowing in the center of the tube The liquid film at the bottom of the tube is much thicker than at the top
Adaptive to low velocity Subjective Transparent tubes required
（4）Annular flow（环状流）
Gas flows in the center of the tube
Liquid partially flows as an annular film on the walls of the tube Liquid partially flows as small droplets distributed in the gas flowing in the center of the tube
1 single liquid phase；2 bubbly flow；3 plug flow； 4 slug flow；5 wavy flow；6 annular flow
The determination or identification methods of Flow patterns（流型确定或流型识别的方法）
Comparisons of gas-liquid two-phase flow patterns in horizontal tube with whole gravity and small gravity（地 球重力和微重力条件下水平管内气液两相流型的比较）
—— Many investigators also defined other flow patterns, and nearly a hundred different names have been used.
Chapter two — Two-phase flow patterns and flow pattern maps （第二章－两相流型和流型图）
Introduction（简介） 1、Flow pattern or flow regime（流型） —— gas-liquid two-phase flow has obvious interface（气液两相流动具有明显的流动界 面） —— has various geometric configurations（ 流动具有各种不同的几何构型）
（5）Slug flow（弹状流）
the upper wall of the tube is alternatively flowing by the gas bubble and liquid phase the wave amplitude is so large that the wave touches the top of the tube Attention: The difference between slug flow and plug flow is: The upper wall of gas bubble has no liquid film in slug
……
3、Flow patterns in vertical upward tubes —— gas and liquid phase both flowing upwards， adiabatic flow（垂直上升管内的流型 —— 气液两相 均向上流，绝热流）
——When the quality is gradually increased from 0 to 1, the flow patterns can be classified:
—— By naked eye (direct method) —— By various types of instrument (indirect method) Gamma-ray densitometer Conductive probe Optical probe Pressure difference signals Capacitance probe High-speed photography and so on.
2、Important physical parameters in determining the flow pattern:（流型）
—— surface tension（表面张力）
Keep channels walls always wet Make small liquid drops and small gas bubbles spherical —— gravity（重力） Tends to pull the liquid to the bottom of the channel especially in non-vertical channel
—— From bottom to top, the flow patterns of steam-water two-phase flow in the tube take turns as follows:
Single phase flow
Bubbly flow Slug flow
Gas phase flows above and liquid phase flows below
（4）Wavy flow（波状分层流）
Gas and liquid phase have obvious interface
The gas-liquid interface is wavy