As expected, the resulting predicted voltage across the anode
assembly indicates that more current is drawn by the center stub
which has a shorter current path to the bath. A typical distribution
through the center plane of the assembly is shown in Figure 10.
The 6 flutes base case results in a predicted voltage drop in the
order of 305 mV, and a cast iron to carbon drop in the order of 30
mV.
Impact of Design
An intuitive way to reduce the cast iron to carbon voltage drop is
to increase the surface area. In reality, the resulting voltage drop
will depend on the interaction between contact area and contact
quality. To illustrate this, an alternative configuration with a
number of flutes increased to 16 was studied. The flutes are
identical to the base case, and all other dimensions were kept
constant. The finite element mesh is shown in Figure 11.
As expected, the resulting current density in the carbon, shown in
Figure 12, reveals a better distribution of current around the
circumference of the stub hole. However, the current density is
visibly still higher in the bottom portion of the stub hole and in the
higher contact pressure zones.
The 16 flutes alternative case results in a predicted voltage drop in
the order of 307 mV.
Discussion
The comparison between the performance of the 6 flutes and the
16 flutes cases is summarized in Table 2. It can be seen that in the
16 flutes case, the reduction of high quality contact area increased
the electrical resistance to the point offsetting the 38.9% increase
in nominal contact area, resulting in a slightly higher anode
voltage drop. It is also interesting to note that the 16 flutes
configuration requires approximately 37% more cast iron than the
base case, which would lead to a decrease of the rodding shop
productivity.