Stratified Flow In Horizontal Pipe Research Articles

Experimental and Theoretical Study of Interface Characteristics of Gas–Liquid Stratified Flow in Horizontal Pipe at High Pressure

Wave stratified flow is widely encountered in processing industry, the interface wave impacts heat and mass transfer between the fluids, and flow pattern transition from it to slug flow makes it difficult to deal with the processing fluids that transported by long pipelines especially. Meanwhile, the interface wave influences the viscous drag forces working on the fluids in the pipe, which is impacted by the characteristics of interface profile, such as wave length, amplitude and propagation speed. Experiment of air–water two-phase flow in horizontal pipe at different pressures (0.1 MPa, 2 MPa) are carried out, the influence of pressure on interface profile characteristics is studied, new models for wave length, amplitude, frequency and propagation speed are proposed and tested, and good performance is proved. Shear stress working on interface wave is theoretically calculated, influence of both fluids superficial velocities and pressure on it are studied, and its influence on wave propagation speed is formulated.

Experimental study of gas-liquid two-phase wavy stratified flow in horizontal pipe at high pressure

The regimes of gas-liquid two-phase flow in horizontal pipe at high pressure were experimentally investigated, and characteristics of wave stratified flow, such as wave length, wave height and propagation speed were calculated. The pressure drop was analyzed and friction factors, such as gas-wall, liquid-wall and interfacial friction factors, were calculated and new correlations were deduced. Influence of interface wave on interfacial friction factor was studied, and characteristics of interface wave were included to deduce new correlation for it, and good accuracy was proved. For the gas-water two-phase flow at 2 MPa, transition from wave stratified to annular flow appears with smaller gas superficial velocity compared with that at atmosphere, and intermittent flow appears with greater liquid superficial velocity. Regime transition models are tested, for the gas-liquid two-phase flow at atmosphere the sheltering coefficient with value of 0.01 is appropriate. However, it is promoted to be 0.06 at 2 MPa, and good performance of regime transition model was reached.

Theoretical and experimental research on interfacial shear stress and interfacial friction factor of gas-liquid two-phase wavy stratified flow in horizontal pipe

The external flow field over wave interface is reached by the aid of conformal transformation thought, and velocity boundary layer of inner flow field is deduced also, which gives fundamental description of shear stress over wave interface. The viscous drag coefficient is induced with considering the characteristics of interface wave, such as wave height, wave length and ratio between wave lengths of both ascending and descending semi periods, which significantly impact the velocity gradient over the wave interface that accounts for the differences in distribution of local shear stress. The influence of fluid flow is studied also, which gives support that the earlier separating point of the fluid flow over wave interface the stronger depression to the turbulent perturbation is made, and a reduced drag force arrived. There are otherness and commonness between fluid flow over wave interface and interface appearing in air-water wave stratified flow, and a new model is proposed to intrinsically construct the interfacial friction factor encountered in wave stratified flow. The models for viscous drag coefficient and interfacial friction factor are tested, different models are studied, predicted values are compared with experimental data and that computed by solving there-dimension unsteady Navier-Stokes equations, which gives proof that the values predicted by newly proposed models well fit the real values.

A model of wax deposition under oil-gas two-phase stratified flow in horizontal pipe

A model of wax deposition based on molecular diffusion mechanism, for oil-gas two-phase stratified pipe flow is developed. In the model, unidirectional fully developed flow analyses of momentum, heat and mass transfer are presented. And, a cube cage model is used to describe the wax deposit structure considering the effect of oil flow shear on the deposit. Calculation of wax deposit is compared well with a flow loop experiment. In particular, the model could give the wax deposit forming a crescent shape at the cross section of pipe, which is observed in different experiments. Furthermore, the cause of forming a crescent shape is revealed, which is indicated by the non-uniform circumferential distribution of mass flux for wax deposition along the pipe wall wetted by the oil. The mass flux from oil bulk flow to the oil-deposit interface is closely related to three parameters, diffusivity at oil-deposit interface, the temperature gradient at the oil-deposit interface at different time, and the slope of the wax solubility curve at oil-deposit interface temperature.

Two instability criteria for the stratified flow in horizontal pipe at cocurrent flow conditions

This paper presents a theoretical approach of two instability criteria from the stratified to nonstratified flow in horizontal pipes at cocurrent flow conditions. The new theoretical instability criteria for the stratified and nonstratified flow transition in horizontal pipe have been developed by hyperbolic equations in two-phase flow. These criteria, onset of slugging criterion and critical flow condition criterion, at cocurrent flow condition correspond to imaginary and zero characteristics which occur when the hyperbolicity of a stratified two-phase flow are broken, respectively. Through comparison between results predicted by the present theory and the Kukita et al.'s experimental data, it is shown that they are in good agreement with experimental data.