| 摘要 |
The heat in an electrical heating wire is transferred by way of radiation, or conduction, or convection. Especially in the case of highly rated elements operating in air, where the temperature of the environment is relatively cold, heat transfer by radiation is predominant. In order to achieve as low element temperature as possible at a given surface loading, it is desirable to raise the emissivity coefficient. The surface coating on an element of which the base material is an alloy containing 10-30 weight % Cr, 2-10 weight % Al, maximum 5 weight % of other alloying elements and balance Fe, according to the present invention consists of metal, metal alloy, metal compound or metal oxide with an emissivity coefficient which is higher than that of aluminium oxide. Different metals could be considered for the surface coating, most suited are nickel, cobalt, chromium and iron. In addition to the increase of the emissivity coefficient also other advantages are achieved, for example improved deformation stability at operating temperature. |
