Figure 7.4. Same as ﬁgure 7.3 but showing changes in the ﬂow regime. boundaries for various pipe diameters: 1. 25 cm (dotted lines), 2. 5 cm (solidlines), 5 cm (dash-dot lines) and 30 cm (dashed lines). From Mandhane etal. (1974).
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Two-phase flow can also occur when the pipe carries two liquids oil and water, for instance-rather than a gas and a liquid. Liquids tend to have more similar density, and as chapter 13 will reveal, liquid-liquid flow can result in more flow regimes than those mentioned so far. Figure 1.2.5 a) and b).
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Figure 7.1. Flow regime map for the horizontal ﬂow of an air/water mix-ture in a 5. 1 cm diameter pipe with ﬂow regimes as deﬁned in ﬁgure 7.2.Hatched regions are observed regime boundaries, lines are theoretical pre-dictions.
http://authors.library.caltech.edu/25021/1/chap7.pdf
The two phase flow conditions are generally high speed flows and dominated by the annular or dispersed flow regimes. The mixture model is a simplified model of the full multiphase model and is considered a good alternative when simulating a dilute flow of droplets of liquid in a gas.
http://www.sciencedirect.com/science/article/pii/S0308016113000793
1.3 Three-and four-phase flow 1.3.1 Types of three-phase and quasi four-phase flow Three phase flow is most often encountered as a mixture of gas, oil and water. The presence of sand or other particles can result in four-phase flow, or we may have three-phase flow with solids instead of one of the other phases.
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7.2.5 Flow pattern classiﬁcations One of the most fundamental characteristics of a multiphase ﬂow pattern istheextenttowhichitinvolvesglobalseparationofthephasesorcomponents.At the two ends of the spectrum of separation characteristics are those ﬂowpatterns that are termed disperse and those that are termed separated.
http://authors.library.caltech.edu/25021/1/chap7.pdf
Figure 1.2.1 illustrates the flow regimes we can encounter in horizontal two-phase gas-liquid flow. Stratified flow has the strongest tendency to occur in downhill or horizontal flow with relatively small gas and liquid flow rates.
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The flow areas between the piston and the valve body and the gland flow areas are strictly three dimensional geometries. However, modelling these as two dimensional equivalent annulus areas as shown on Fig. 2 has been found adequate as indicated in the single phase studies of Dempster et al. (2006) [4] .
http://www.sciencedirect.com/science/article/pii/S0308016113000793
3. Computational model. The two phase flows which occur in the valve are dominated by the accelerating gas flows as the gas expands through the valve. This creates a high speed highly dispersed droplet or droplet/film flow in the small flow area paths of the valve.
http://www.sciencedirect.com/science/article/pii/S0308016113000793
1. Safety relief valves (SRV) are designed and used to protect a pressurised system against excessive operating pressure and must open at a maximum of +3% of a predetermined set pressure and close within −10% of the set pressure to meet ISO standard requirements (for single phase flow conditions).
http://www.sciencedirect.com/science/article/pii/S0308016113000793
when does two phase flow occur
Two phase flow occurs when the pipe carries two liquids oil and water, for instance-rather than a gas and a liquid.