The Tube Inlet Erosion-Corrosion study at UQ has provided ameliorative measures for installation on QAL’s Heat Exchangers. The installation of the Prismatic Flow Correction Device reduced damage on the tube inlets, however, created problems elsewhere in the header. The reduction in damage to the tube inlets can be used to study the governing mechanisms of erosion-corrosion in a real life application. A comparison of hydrodynamic parameters before and after the prism installation can give an insight into the mechanisms of erosion-corrosion and this is the focus of the current project. The thesis objectives are
• To create a model to assist with the visualisation of the cross flow patterns near the tube inlets in order to better understand erosion-corrosion mechanisms
• To use data from experimentally-verified near-tube sheet flow patterns at five locations for velocity inlet initial conditions.
• To Qualitatively assess the potential for damage at the tube inlets from the flow patterns observed, particularly flow separation in the tubes and the regions immediately surrounding the tube inlets.
• To identify differences in flow patterns caused by the installation of the prismatic flow correction device and the implications to erosion-corrosion mechanisms.
A modelling process labelled the LEGOTM process by the author was used to create a suitable model for running CFD Simulations. This process involved the creation of accurate model geometries of the region surrounding the tube inlets. Five Locations were chosen to cover a wide area of the Tube Sheet and the flow information for the initial conditions was obtained from experimentally verified numerical simulations.
The commercially available CFD package FLUENT was used to simulate the flow patterns near the tube sheet. Velocity Inlet conditions were approximated based on experimentally-verified CFD data from a previous study. A qualitative assessment was performed and evidence of erosion-corrosion mechanisms was found as predicted by previous studies. Only six models were run successfully and a direct comparison between the normal model and the prismatic model could only be performed for two locations.
The information obtained, however, proved to be valuable in identifying the governing factors in erosion-corrosion as described by researchers in the field. The qualitative assessment identified Location 2 as a ‘hot spot’ for erosion-corrosion damage even after the installation of the prism. Location 3 demonstrated the change in flow patterns and how these changes reduced the turbulent kinetic energy and angle of incidence, both thought to directly contribute to the erosion-corrosion damage observed in the heat exchangers.