Simulation of Two Phase Flow Boiling in Small Channels

Simulation of Two Phase Flow in Pipelines

Why we use two phase flow pipelineif both gas and oil are being produced we need two pipelines- it may be costly specially for offshore- so use one pipeline which carries both-two phase.

Critical Problems with two phase pipe in briefMain problem pressure drop fluctuations so proper estimate of pressure drop is necessary.

Two Phase Flow Regimes(read notes in slide)

Bubble flow in which the gas is dispersed as small bubbles throughout the liquid which is the continuous phase.Plug flow which is an intermediate between bubble flow and slug flowSlug flow in which the individual small bubbles have started to coalesce together in the form of slugs. The liquid phase is still continuous.Stratified flow in which the gas occupies the top half of the pipe and liquid occupies the bottom halfWavy flow in which the increasing gas flow rate causes ripples to form on the surface of the liquid.Annular flow in which the fast moving gas stream is now a continuous phase that encompasses central portion of the tube with the liquid forming a relatively thin film on the tube well.Mist flow in which the velocity of the continuous gas phase is so high that it reaches as far as the tube wall and entrains the liquid in the form of droplets.

4CFDWe used Ansys Fluent for CFD.We carried out two simulations2D Transient : To look at the changes with respect to time3D Steady State : To calculate pressure drop in the pipeline3D simulations carried out for volume fraction range 0.1-0.9

Mesh GenerationExplain some basics about meshMesh was created in ICEM

E-E ModelIt solves conservation equation for mass, momentum and energy for each phase.In our case:Continuous Phase : LiquidDispersed Phase : Vapor

Separate phases are treated as interpenetrating continua.This means that at a certain position, all phases can be present with a certain volume fraction, and no clear interface between the phases can be established.Equations for different phases are coupled using pressure and phase interactions.

7Conservation Equations of Mass and Momentum

Phase Interaction ModelsInterfacial ForcesDrag ForceLift ForceSurface Tension Force

Model Space DimensionsThe model to be simulated is a 3D

The starting .1m is inlet to let inlet water to stabilize.Next 10m is the pipe region.The last .2m is extended region so as to reduce reversed flow.0.1m10m0.2m

Boundary ConditionsWallImpermeable WallInletVelocity InletMass FlowOutletPressure Outlet

Correlations UsedLockhart & Martinelli Correlation

Friedel Correlation

RESULTS

Velocity Contours

Velocity Contours

Velocity Contours

Velocity Contours

Velocity Contours

Velocity Contours

Pressure Contours

Pressure Contours

Pressure Contours

Pressure Contours

Pressure Contours

Pressure Contours

Pressure Contours

Volume Fraction Contours

Volume Fraction Contours

Volume Fraction Contours

Steady State Simulations:

Volume Fractions

Comparison of Pressure Drop

Volume FractionLockhart Martinelli FriedelCFD0.12.21462.3623372.2320.22.17312.5490672.080.31.972.542172.0010.41.69492.4123411.8630.51.37592.1875091.2370.61.04191.8810851.0310.70.71381.5003530.78120.80.41141.0506150.43210.90.390.5396770.4112

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