Calculation of Critical Thickness of the Protective Shell of the Cylindrical Electric Heating Element

The mathematical model of non-stationary process of heat conduction in an electric heating element is considered. The element is a cylindrical conductor with a protective ceramic coating sputtered on its lateral surface. The conducting layer of the electric heating element generates heat of the volumetric power depending on electric current. The heat extracts from a surface of protective coating according to the Newton law. The contact surface between layers is assumed to possess known thermal resistance and thermal physical properties of materials depend on temperature. Influence of geometrical and thermo physical parameters of the model on the evolution of the electric heating element temperature has been studied, operating modes of heating without melting the conductor being determined. A critical value of the protective ceramic coating thickness at which temperature on the axis of the conductor reaches the melting temperature is defined.

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