based thermo-electro-mechanical anode stub hole design tool [1],
an ANSYS based thermo-electro-mechanical collector bar slot
design tool has been developed. Since the average contact
resistance at the cast iron/cathode block interface is higher than the
contact resistance at the cast iron/anode carbon interface, the
potential for mV savings is even greater.
different collector bar slot configurations. The results obtained are
presented.
problem, issues related to the cathode collector bar slot cast
iron/carbon contact resistance have not been the subject of
numerous publications in recent years.
graphitized cathode blocks, the voltage drop due to the contact
resistance represents more in percentage of the total cathode lining
drop than the voltage drop due to the contact resistance represents
in the total anode voltage drop. There should be room for further
reduction of that lining voltage drop like it is the case for the anode
voltage drop by using the thermo-electro-mechanical (TEM)
collector bar design tool to optimize the cathode slot design.
to instrument the cathode lining in order to measure the contact
resistance between the cast iron and the cathode carbon in the
collector bar slot. Boivin [3] did instrument a collector bar (see
Figure 1 and 2 of his 1985 TMS paper) and indirectly measured 6.6
µ-ohm m2 assuming a uniform contact resistance value on all three
dependent upon applied pressure, one have to assume that most of
the current passes through the vertical cast iron-to-carbon contact
interfaces but there are no references on experimental
measurements that will confirm that.
measurements to confirm what is the true situation, when
developing a thermo-electric cathode lining model, the author kind
of arbitrarily assumed that the contact resistance on the top
horizontal interface was twice the value of the contact resistance of
the two vertical interfaces.
make this kind of arbitrary assumption by calculating the contact
pressure and then the corresponding contact resistance value based
on some temperature and pressure dependant relationship [5].
presented last year [1], the TEM cathode collector bar slot model is
based on the usage of ANSYS® SOLID226 3D thermo-electro-
TARGE170 thermo-electro-mechanical contact pair elements.
CONTA174 element supports the setup of a pressure and
temperature TCC (thermal contact conductance) and ECC
(electrical contact conductance) values through the %table%
option.
and the TEM cathode collector bar slot model is the topology
which is quite easy to build and when needed to modify using
ANSYS® parametric design language (APDL).
last year paper [1] is the selection of the thermal expansion
reference temperatures. Contrary to Richard [5] who is creating a
model geometry that corresponds to the room temperature
geometry and hence is incorporating an air gap between the cast
iron and the carbon (anode carbon in his case), the model geometry
in the present work was constructed without incorporating an air
gap between the cast iron and the carbon corresponding to the
geometry when the cast iron has solidified.
contact pressure of the unit (either anode or cathode) in operation,
the material reference temperatures to calculate the thermal
expansion must be set differently than in Richard's model. In that
model incorporating a room temperature air gap, the reference
temperature of all materials is the room temperature while in the
present model that does not incorporate a room temperature air gap,
the reference temperature of the cast iron is its solidification
temperature (Ts in Equation 2 of [6]). The reference temperature
of the other materials (stub and anode carbon or collector bar and
cathode carbon block) is the average temperature of those materials
when the cast iron solidified (like Ta in Equation 1 of [6]; notice
that Equations 1 and 2 in [6] assume that the effective anode
carbon temperature at cast iron solidification is To the ambient
temperature which is a simplification not made in the present
work).