Comparing the efficiency of air-cooled heat exchangers for bottom electrodes of dc arc furnaces

Bottom electrode is a basic component of a DC arc furnace; located on the bottom axis, it supplies electric current to the charge or to the liquid metal. Some designs feature dual bottom electrodes displaced from the bottom axis to improve the efficiency of mixing the melt at the bottom. Bottom electrodes are water-cooled. One of the significant drawbacks of DC arc furnaces is the risk of explosions that may be caused by the interaction of molten metal and water in case of emergency, when metal exits the furnace via the bottom. An alternative option for rod electrodes consists in forced electrode cooling by placing an air-cooled heat exchanger on the copper portion of the electrode; such heat exchanger is a finned surface. The paper dwells upon such designs where bottom electrodes are cooled by ring fins, straight fins, or pin fins. The fin cross-section may be of different profiles: rectangular, trapezoid, hyperbolic, triangular, etc. Computer simulation for each heat-exchanger type has produced temperature distribution over the fin vertical, thermal power dissipated by the fin (or pin), fin efficiency and mass as a function of its geometry. Analysis confirms the possibility of altering the design of rod electrodes by switching from water-based cooling to air cooling, which is especially applicable to DC arc furnaces under 10 tons. Comparison of different air-cooled heat-exchanger designs that pin fins and ring fins are advantageous in terms of heat dissipation and material intensity.