Cooling of arc furnace electrodes with heat pipes

Combination electrodes with water cooling shanks, which have been introduced to reduce graphite consumption in UHP furnaces, cause the danger of vapour explosions in case of breaking. Heat pipes are highly efficient two phase heat conductors which could provide a safer alternative to water cooling shanks, since they contain only a small amount of liquid. The transport of energy results from evaporation of the working fluid in the heated section, convection of the vapour to the cooled section and reflux of the condensed fluid to the heated end. Large heat quantities can be transferred under nearly isothermal conditions within the tube, as long as certain limits are not exceeded. The operating temperature can be controlled by design parameters such as the thermal resistance of the cooling zone. The proper function of heat pipes for cooling arc furnace electrodes is investigated by comparing the calculated heat load with temperature dependent limits to heat transport. It is shown that copper tubes with water as the working fluid combine efficient cooling and safe performance in the low temperature range, while the cheaper steel tubes with sodium filling are suitable for high temperature operation.