Multiphase Flow Properties & Pressure Gradient Calculation - Production Technology
In fluid mechanics, two-phase flow is a flow of gas and liquid — a particular example of Similar differences are typical of water liquid/water vapor densities. flow · Buckley–Leverett equation · Darcy's law for multiphase flow (for flow through. Analysis of two phase flow systems is complicated by the appearance and . the liquid phase energy equation is .. + g g is the effective two-phase density ρ. In the next paragraphs, two-phase flow properties (holdup, densities, Then the pressure gradient equation which is applicable to any fluid.
Three equations for two-phase density are used by various investigators in two-phase flow: Calculation of the two-phase viscosity requires knowledge of the liquid holdup.
Two equations for two-phase viscosity are used by various investigators in two-phase flow: General Pressure Gradient Equation: This equation is usually adapted for two-phase flow by assuming that the two-phase flow regime and two-phase properties can be considered homogeneous over a finite volume of the pipe.
Many correlations have been developed for predicting two-phase flow pressure gradients which differ in the manner used to calculate the three terms of pressure gradients equation elevation change, friction, and acceleration terms: No slip, no flow regime considerations: No distinction is made for different flow regimes.
Mixture Density - Two-phase Flow
Slip considered, no flow regime consideration: The same correlations for liquid holdup and friction factor are used for all flow regimes.
Slip considered, flow regime considered: Usually a different liquid holdup and friction factor prediction methods are required in each flow regimes.
Starting with the known inlet pressure and flow rates. Calculate the average pressure and, for non-isothermal cases, the average temperature in the increment. Determine the gas and liquid properties based on black-oil or compositional model at average pressure and temperature conditions.
Slip ratio (gas–liquid flow) - Wikipedia
If they are not sufficiently close, estimate a new value and return to step 3. Repeat the steps 2 to 7 for the next pipe length increment. Flow Correlation Information Multi-phase flow correlations are used to predict the liquid holdup and frictional pressure gradient.
- Mixture Density – Two-phase Flow
- Slip ratio (gas–liquid flow)
- Multiphase Flow Properties & Pressure Gradient Calculation
If pressure drops further, which can happen locally near the vanes for the pump, for example, then a phase change can occur and gas will be present in the pump. Similar effects can also occur on marine propellors; wherever it occurs, it is a serious problem for designers. When the vapor bubble collapses, it can produce very large pressure spikes, which over time will cause damage on the propellor or turbine.
The above two-phase flow cases are for a single fluid occurring by itself as two different phases, such as steam and water. The term 'two-phase flow' is also applied to mixtures of different fluids having different phases, such as air and water, or oil and natural gas.
Sometimes even three-phase flow is considered, such as in oil and gas pipelines where there might be a significant fraction of solids. Although oil and water are not strictly distinct phases since they are both liquids they are sometimes considered as a two-phase flow; and the combination of oil, gas and water e. Other interesting areas where two-phase flow is studied includes in climate systems such as clouds and in groundwater flow, in which the movement of water and air through the soil is studied.
Other examples of two-phase flow include bubblesrainwaves on the seafoamfountainsmoussecryogenicsand oil slicks. Characteristics of two-phase flow[ edit ] Several features make two-phase flow an interesting and challenging branch of fluid mechanics: Surface tension makes all dynamical problems nonlinear see Weber number.Two-Phase flow
In the case of air and water at standard temperature and pressurethe density of the two phases differs by a factor of about The sound speed changes dramatically for materials undergoing phase change, and can be orders of magnitude different.