Dianchuan Xing

Characteristics of slug flow in narrow rectangular channels under vertical condition

Gas-liquid slug flow is widely encountered in many practical industrial applications. A detailed understanding of the hydrodynamics of gas slug has important significance for modeling of the slug flow. Non-intrusive flow visualization using a high speed video camera system is applied to study characteristics of slug flow in a vertical narrow rectangular channel (3.25×40 mm2). Ideal Taylor bubbles are hardly observed, and most of the gas slugs are deformed, much more seriously at high liquid superficial velocity. The liquid film thicknesses of left and right narrow sides surrounding gas slug are divergent and wavy, but it has weak effect on liquid film velocity. The gas and liquid velocity as well as the length of gas slug have significant effect on the separating liquid film thickness. The separating liquid film velocity is decreased with the increase of gas superficial velocity at low liquid velocity, and increased with the increase of liquid superficial velocity. The film stops descending and the gas su...

Experimental investigations of single-phase and two-phase flow resistance in narrow rectangular duct under rolling condition

Effects of rolling motion on single-phase and two-phase flow resistance were compared experimentally under ambient temperature and pressure. In the single-phase flow experiments, the different pump head was obtained by a variable speed electromotor, and the flow rate was adjusted combining with a regulating valve. However, for the two-phase pressure drop measurements, the pump delivering water operated with an invariable pressure head of 48m, in order to neglect the effect of pump head on flow fluctuation. The results indicated that effects of rolling motion on single-phase flow resistance depend on the pump head. The fluctuation amplitude of flow rate and frictional pressure drop decreases rapidly as the pump head increases, finally, the flow will tend to be steady if the pump head dramatically exceeds the additional pressure drop. Different from the case of single-phase flow, transient frictional pressure drop of two-phase flow fluctuates synchronously with the rolling motion when liquid Reynolds number...

Flow regimes of adiabatic gas-liquid two-phase under rolling conditions

Characteristics of adiabatic air/water two-phase flow regimes under vertical and rolling motion conditions were investigated experimentally. Test sections are two rectangular ducts with the gaps of 1.41 and 10 mm, respectively, and a circular tube with 25 mm diameter. Flow regimes were recorded by a high speed CCD-camera and were identified by examining the video images. The experimental results indicate that the characteristics of flow patterns in 10 mm wide rectangular duct under vertical condition are very similar to those in circular tube, but different from the 1.41 mm wide rectangular duct. Channel size has a significant influence on flow pattern transition, boundary of which in rectangular channels tends asymptotically towards that in the circular tube with increasing the width of narrow side. Flow patterns in rolling channels are similar to each other, nevertheless, the effect of rolling motion on flow pattern transition are significantly various. Due to the remarkable influences of the friction s...

Study on the Characteristics in the Liquid Slug of Rising Slug Flow in Narrow Rectangular Channel

Gas-liquid slug flow is widely encountered in many practical industrial applications. A detailed understanding of the hydrodynamics of the liquid slug is of great importance in modeling the slug flow. A visualized study using a high speed video camera system was conducted to study liquid slug characteristics of slug flow in a vertical narrow rectangular channel (3.25×40mm2). It is found that three regions could be distinguished in the stable liquid slug tagging along the leading gas slug in most cases. The characteristics of a gas slug are greatly influenced by its position in the liquid slug, and the leading slug has a significant effect on the trailing slug in laminar or transition flow. The wake region of leading slug is also actually a sudden enlargement region where the water jet out of the liquid flim. The minimum stable liquid slug length Lmin is obtained in the experiments ranging from 9 to 17Dh in fully developed turbulence flow.Copyright