Emissive Carbon Coating for Energy Saving

Emissive carbon coating was prepared using a carbon black powder and a phenolic resin binder suspension. Interior of an alumina tube with an emissivity of 0.75 was coated with the emissive coating and its energy saving performance was investigated using a vacuumed alumina tube up to 1000℃. The vacuumed cavity temperature of the carbon-coated alumina tube embedded in an electrically heated furnace was always higher than that of the uncoated one for the same surface temperature of the tube. The cavity temperature difference between the carbon-coated and uncoated tube increased with the surface temperature of the alumina tube. At the surface temperature of 1000 ℃, the cavity temperature difference reached about 20℃. Heating the carbon-coated alumina to raise the cavity temperature from an ambient temperature to 1000℃ at a constant heating rate of 5℃/min yielded an energy consumption of 559 Wh, while the uncoated one resulted in energy consumption of 595 Wh. As the holding time to maintain the cavity temperature of 1000℃ was extended to 120 min, the energy-saving increased from 6% to 11%.