Abstract

The flow characteristics and corrosion evolution under various geometrical configurations of a cylindrical steel annular band exposed to an axial flow of a saline solution at low Re number, were simulated to assess its performance to be used as electrochemical cell reactor. A section of the external wall of the annular cavity is a counter electrode for a working electrode which is a steel band embedded in a concentric internal cylinder. The practical considerations incorporated in the simulated system are, a flow entrance for a model through four perpendicular ports, and a closed loop flow system circulation between the flow cell and a storage vessel. The simulation study explores alternatively a laminar and a selected turbulent model; both cases are combined with a corrosion mechanism in the annular band surface based on a dissolved oxygen reduction as a counterpart redox reaction for iron oxidation. From the simulation's studies, three different regions were identified for the flowing flow through the cell, an entrance disturbed region, an intermediate region characterized by a decreasing radial variability of the velocity between the inlet to the outlet, and an outlet region exhibiting local asymmetry. In considering the low gradients of dissolved oxygen concentration inside the flow cell, a simplified model is probed to be adequate for transient simulation. Selected aspects related to corrosion inhibition because of an oxide layer formation on the band surface, annular band position inside the flow cell to minimize corrosion disturbances, and arguments to justify many basic assumptions and recommendations for geometric configuration of annular cells are discussed.