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have a notable effect on the local temperature distribution in the lining, contributing to
the "cold corner" effect.

This problem of vertical potshell deformation in high amperage cells is

significant enough to induce some smelters to take active measures in order to reduce its
impact. Two of such measures are the usage of cooling fins and that of forced-air
sidewall cooling system. Contrary to the "popular belief", those two measures are not
affecting the cell heat balance, since cooling the sidewall temperature simply induces the
cell to grow more ledge in order to maintain its steady-state superheat and hence global
heat loss. However, these measures not only reduce thermal gradients in the shell wall
but also reduce the temperature in this area. This helps the steel retain its strength [6] and
reduces creep in the shell wall.

In the present study, the efficiency of the cooling fins and the forced-air sidewall

cooling system to reduce the vertical deformation of the potshell in operation has been
analyzed for 300 and 500 kA cell designs.

FINITE ELEMENT MODELING APPROACH

As mentioned previously, the prediction of the mechanical response of an

operating cell is a challenging task. As a first approximation and for comparison
purposes, a simple "Empty-Shell" modeling approach was used [7].

A quarter shell was modeled using four-nodes quadrilateral Finite Strain shell

elements (SHELL181) in the commercial code ANSYS. The corresponding symmetry
boundary conditions were imposed, while one point was supported in the vertical
direction on the second closest cradle to the end wall. A constant downward pressure was
applied on the shell floor to represent the combined weight of the lining and the liquids.
A constant outward pressure was applied to the shell wall opposite to the cathode block
to represent the effect of the lining expansion. The cradles were considered welded to the
shell.

The temperature distribution obtained from the full cell coupled thermo-electric

model was applied as a body load to the shell and cradles [8].

A temperature-dependent isotropic hardening von Mises plasticity law with non-

linear hardening was used (the MISO option in ANSYS). The stress-strain curves at
different temperatures were obtained from [9]. Time-dependent phenomena such as creep
were neglected.

The non-linear finite element problem was solved in 100 load steps. Each step

required typically 4 Newton-Raphson iterations. The linearized system was solved using
an iterative preconditioned conjugate gradient solver (the ANSYS pcg).