A FUNDAMENTAL CONVECTIVE-DIFFUSION BASED MODEL TO EXPLAIN INTERFACIAL MIXING IN MULTIPRODUCT PIPELINES

摘要

Interfacial contamination of batches of refined petroleum products transported throughmultiproduct pipelines is a long standing problem in the petroleum industry. Determination of the extentof mixing depends on various factors including the fluid properties, operating conditions and the flowregimes. The convective-diffusion model along with a fictional parameter introduced by Sir G. I.Taylor, known as the axial dispersion coefficient is the commonly employed methodology to evaluatelongitudinal mixing. However, the model is formulated with a uniform turbulent or laminar flow acrossthe entire flow field. This study argues that the assumption of a uniform flow regime leads toinaccuracies in predicting the extent of contamination at the interface. This study incorporates both theturbulent and the viscous effects in predicting the interfacial contamination volume. Taylor’s analysis ofdispersion coefficients has been reviewed, and an improved model combining the weighted effects ofthe viscous boundary layer contributions and the turbulent core contributions to axial dispersion isproposed. The proposed model provides a possible explanation for the underlying physics of flowthrough straight pipes without pipe fittings and other devices. A comparison of the model predictionswith literature data demonstrates the importance of considering both turbulent and viscous effects toachieve better overall prediction accuracy.