Selecting the design and material for the heating elements of electric resistance furnaces

Conclusions

• 1. The optimal profile and massiveness of the heater section can be selected using Eqs. (7)–(12).

• 2. In the majority of cases, a circle (wire) should be considered the optimal profile of the HE section. A rectangle (strip) may offer an advantage over a circle in cases where the HE is used at temperatures close to the maximum allowable, and with significant "HE/heated-component" temperature gradients, and when negligible metal is consumed by the heating elements.

• 3. As compared with iron-chromium-aluminum He, chromium-nickel resistance alloys are preferred for the fabrication of HE for electric forced-heating furnaces, for charges of high heat capacity, for electric furnaces with an oxidizing atmosphere, at high (150°C and above) temperature gradients between the heat-emitting and heat-receiving surfaces, for high (above 2.0 W/cm²) specific HE surface capacities, and for furnaces with charges having a large heat-receiving-surface area and a high degree of blackness.

• 4. In developing new resistance alloys, we should strive to provide them with a high degree of blackness, which increases with increasing temperature.

• 5. In developing refractories and heat-resistant steels for the fabrication of intrafurnace components and designs that are not heat-emitting, conversely, it is necessary to reduce their degree of blackness, since this will make it possible to reduce their temperature and increase their service lives.