Program Agenda:
1100–1130 Registration and Networking
1130–1300 Lunch
1145–1200 Technical Section Updates
1200–1300 Presentation and Q&A

Abstract:

The Butler-Volmer equation for surface electrochemistry potential and Laplace equation for electrolyte solutions have been available in CFD code for a while, but the challenge remains to find a numerically affordable way to model the mass-transfer-limited corrosion rates. Mass-transfer coefficient using the Sherwood number (Nesic et al., Corr Sci., 1996) approach seems promising, but it is limited by the use of average pipe velocity values, which is unable to differentiate local flow changes in geometries like pipe bend and welding locations. Conventional methods use the wall shear stress as the surface mass transfer parameter, but it was found that the shear stress is a strong function of flow velocity and the resulted corrosion rates are too sensitive to velocity changes. A consistent rate-limiting expression cannot be found even for flows in a straight pipe.  A better method is proposed to use the mass-transfer coefficients as the limiting mechanism for corrosion. However, the mass-transfer coefficient can be expressed in various forms and their values can be sensitive to boundary layer thickness. It was found that by using the scalable wall function model it is possible to have a consistent rate-limiting formulation for corrosion rates. The comparison to experimental results [Zhang et al. Corr. Sci., 2013] showed that the hybrid model can predict the corrosion rate with reasonable accuracy. This method effectively addresses the drawbacks of the Sherwood number approach, and avoids the costly computation needed to accurately predict the wall shear stress. Further validations with the experimental data by Nesic et al. [1996] were also satisfactory demonstrating the validity of the mass-transfer limited approach. However, it should be noted that wall shear stress and mass transfer may have different impacts on the types of corrosion chemistry involved depending on how the mechanism of surface chemistry alters the metal morphology.

Reference

Nesic et al., Corrosion Science 52, pp. 280-, (1996).

Zhang et al., Corrosion Science 77, pp. 334-, (2013).

Speaker Bios

Kuochen has a Ph.D. in mechanical engineering from SUNY Stony Brook, and has been working in the area of fluid dynamics modeling for the past 20 years. Spent 9 years with Dow Chemical working on a bunch of reactor designs and modeling, then joined Shell in 2006. His work spans from fundamental research of turbulent reacting flows to applications of CFD models to industrial problems including polymeric flows, crystallization, burner design, sand transport, hydraulic fracturing, reservoir flows and biofuels. He pioneered the application of Monte-Carlo PDF methods to polymer reactor design and the use of Lagrangian model for dense slurry flows. His recent works involve the development of biofuel reactors using woodchips and the study of water droplet dispersion in subsea oil pipelines. He has authored more than 40 research papers for scientific journals and conferences.