The purpose of this thesis was to examine the problems experienced by Queensland Alumna Limited (QAL) in their shell-and-tube heat exchangers. The problems were caused by a process known as erosion-corrosion, with the damage a result of a two stage process. The first being the erosion of the protective surface film by fluid flow and the second being the electrochemical corrosion of the base metal. Erosion-corrosion is complex and different researchers have concluded that different mechanisms are the cause. In this study Computational Fluid Dynamics (CFD) was utilized to investigate the hydrodynamic parameters affecting the flow in QAL's heat exchangers.
CFD is becoming a widespread tool, used by a vast number of engineers. With the development of computer technology, numerical methods can provide answer to many problems, with numerous advantages over other options. Disadvantages though, do exist, due to the fact that CFD uses computers to solve mathematical models for the governing equations of motion of the flow.
The problem faced by QAL initially existed in the tube bank of the first pass of the heat exchanger. A prismatic correction device was proposed and installed to resolve this situation. However, a further problem was experienced on the header shell due to this correction device. This study looked at deflectors, which modified the flow direction at the inlet to the header. It endeavoured to determine a solution, which rectified both these problems without causing any additional problems.
The six modifiers investigated, the ten degree, the thirty degree, the forty-five degree, the sixty degree, the curved and the backwards, all produced adverse results within the heat exchanger. The increased amounts of swirl and/or velocity led to higher turbulence, which would have caused erosion-corrosion on varying parts of the header. This eliminated these options as potential solutions to the problems.