Direct Resistance Heating Characteristics of Rectangular Sheet Blanks

The results of an investigation of the characteristics of heating rectangular sheet blanks by the direct passage of current are presented. An analysis of the thermal characteristics based on the heat-transfer equation of a material with internal heat generation produces data for temperature distribution and heat balance at any instant of the heating process. The instantaneous temperatures detennined by experiments are in good agreement with those obtained from the theoretical analysis. The results indicate that a uniform temperature rise over the bulk of the strip can be obtained with larger currents per unit width. The overall efficiency is expressed as a product of indicated thermal efficiency which relates to the heat transfer characteristics of the strip, and electrical transmission efficiency which relates to the electrical characteristics of the heating system. Results are given for the dependence of indicated thermal efficiency on the speed of heating and the length of the strip, as well as for the variation of electrical transmission efficiency with the length of the strip.