Modeling the Transfer of Radiant Energy to a Bulk Medium in Electric Furnaces with the Upper Position of Radiating Eleme
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Vol. 61, No. 1, May, 2020
MODELING THE TRANSFER OF RADIANT ENERGY TO A BULK MEDIUM IN ELECTRIC FURNACES WITH THE UPPER POSITION OF RADIATING ELEMENTS A. I. Nizhegorodov1,2 Translated from Novye Ogneupory, No. 2, pp. 10 – 14, February, 2020.
Original article submitted November 26, 2019. A new design of suspended radiating elements is developed for heating systems of electric furnaces with moving hearth platforms and modular-trigger furnaces. The transfer of radiant energy on the surface of firing modules and on the flow of expansible vermiculite is simulated. Analytical dependencies are obtained to calculate the temperatures of radiating elements, a refractory base, a heat-insulating cover, and grains of the material itself. The performance of modular-launch furnaces may significantly increase because the crowding of vermiculite in areas where firing modules are poured does not lead to the burnout of radiating elements, as observed in tape nichrome systems. Keywords: electric furnace, heating system, radiating elements, radiant energy transfer, balance flow method, angular coefficient
sions under thermal covers [2]. This design will fundamentally change the conditions for the transfer of thermal energy into a medium being processed. Therefore, two tasks are set in this study: (1) modeling the transfer of radiant energy on the surface of firing modules and vermiculite flow and (2) obtaining analytical dependences for calculating the temperatures of radiating elements and expansible grains.
INTRODUCTION Studies on the electrical modules of vermiculite kilns have revealed the disadvantages of using tape nichrome as elements radiating energy, mounted on an edge, and creating constrained conditions for material movement. Expansible vermiculite during movement is in contact with the walls of radiating elements heated to a high temperature, leading to carbon deposit formation and nichrome burnout. In areas where a material is poured from one module to another, crowding of particles is formed, and they overlap with the walls of radiating elements in height; consequently, the same result is obtained [1]. Constrained conditions provide the possibility of congestion and the formation of vermiculite plugs between adjacent walls; as a result, local overheating and melting of radiating elements occur occasionally [1]. Furnace failures due to nichrome melting entail labor-consuming repair and result in prolonged downtime. As such, the design of firing modules should be improved, and a new heating system should be created with the upper position of the radiating elements mounted on special suspen1 2
UPPER HEATING SYSTEM DESIGN OF THE FIRING MODULE A new system of suspended radiating elements is developed for electric furnaces with movable hearth platforms [2] installed at an angle of 19° – 20°. Figure 1 presents a fragment of the furnace and explains its structure and capabilities. The radiating elements 1 are located between a platform 2 and a thermal cover 3 made of a ceramic–vermiculite plate [3] edged with a metal bracket
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