Abstract

Transient simulation of two-phase gas-liquid flow in pipes requires considerable computational efforts. Until recently, most available commercial codes are based on the two-fluid model which includes one momentum conservation equation for each phase. However, in normal pipe flow operation, especially in oil and gas transport, the transient response of the system proves to be relatively slow. Thus it is reasonable to think that simpler forms of the transport equations might suffice to represent transient phenomena. Furthermore, these types of models may be solved using less time-consuming numerical algorithms.

Highlights

  • Transient simulations of gas-liquid flow in pipelines involve elaborate computer codes, the design and use of which demand tremendous effort

  • Developed in Norway (Bendiksen et al 1987, 1991), OLGA is a two-fluid model with an additional momentum equation for the droplet field

  • The Drift Flux Model is derived from the Two-Fluid Model by neglecting the static head terms DPG and DPL in the last two Equations (3) and (4) and replacing the two momentum equations by their sum

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Summary

INTRODUCTION

Transient simulations of gas-liquid flow in pipelines involve elaborate computer codes, the design and use of which demand tremendous effort. The resulting code TACITE is meant to become a commercial product (Pauchon et al 1993, 1994) Another drift flux model, TRAFLOW, developed by the Shell Oil Company, should be mentioned. Fast transients associated to Loss Of Coolant Accidents (LOCA) are of major interest, while in the oil and gas industry, the interest often lies in relatively slow transients, associated with the transport and subsequent release of slugs at receiving facilities Under these conditions, one may consider the momentum equation to be a steady state force balance, leading to simpler and less elaborate calculations. – A Drift Flux Model (DFM), based on one momentum conservation equation and an algebraic slip relation. As for accuracy, it is defined in terms of the operating variables which are most significant for the end user, that is, the peak in outlet liquid flowrate subsequent to an increase in the inlet gas flowrate

THE TWO-FLUID MODEL
Transport Equations
Numerical Scheme
THE DRIFT-FLUX MODEL
THE NO-PRESSURE-WAVE MODEL
COMPARISONS OF THE MODELS
Transient Response of Models for the Reference Case
Comparison with Experimental Data
Severe Slugging Case
CONCLUSION
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