Abordagem algébrico-diferencial na simulação unidimensional do escoamento bifásico em dutos

Abstract

Simultaneous flows of liquid and vapor phases through pipes, ducts and channels are frequently encountered in industrial applications, as is the case of petroleum production and refining, transportation of natural gas and nuclear power reactors. Simulation and design of such process facilities demands that efficient and accurate numerical methods be applied to equally accurate two-phase flow mathematical models. A literature survey has shown that this problem has been currently addressed by means of one-dimensional simulations based predominantly on Two-Fluid and Drift-Flux Models, although simpler methods which employ the assumption of homogeneous flow are also seen to persist. The present study proposes that these calculations, which are currently based on finite-volume discretizations and iterative sequential procedures, be performed instead by simultaneously solving all equations of change and constitutive models using established numerical methods devised for Differential-Algebraic Equations (DAE) systems. Through objective comparisons between this strategy and the finite-volume based technique, the DAE approach was proved highly advantageous in terms of computational requirements and accuracy of results for steady-state test cases. The proposed method was subsequently employed in the assessment of experimental data reproducibility with the Two-Fluid, Drift-Flux and Homogeneous models. Most accurate results were obtained with the Drift-Flux Model, thus making that approach even more atractive given its simpler formulation as compared to the Two-Fluid Model. It is lastly demonstrated through discussions and results that the proposed Differential-Algebraic Approach can also be extended to allow for efficient dynamic simulations of two-phase flow.