Abstract
Intermediate heat carriers have been applied in engineering as enhanced heat transfer elements, but their theoretical analysis still needs to be improved. Therefore, an intermediate heat carrier is added to establish the quaternary model of the furnace gas under nongray radiation characteristics. Based on this model, an analytical expression of heat flux on the surface of the billet is derived. General rule of the impact of intermediate heat carrier on the thermal efficiency in the furnace can be properly derived by analytical calculation from a theoretical point of view. The results show that the longer the length of the intermediate heat carrier located at the top of the furnace, the greater the heat exchange capacity on the surface of the billet. Meanwhile, when the intermediate heat carrier is located in the center of the furnace top, the billet gets higher heat flux; the closer to both sides, the lower the heat flux. In addition, the influence that the surface emissivity of the intermediate heat carrier has on the heat transfer of the billet surface is related to the values of εg and αgw. Comparison with previous literature shows that adding intermediate heat carrier can improve the heat exchange capacity of billet.
Highlights
In order to reduce carbon dioxide emissions from iron and steel enterprises and improve the thermal efficiency of heating furnace, increasing radiation from furnace wall is an effective method that needs more attention [1]. e thermal efficiency of heating furnace depends on many factors, among which, the appropriate shape of furnace can maximize the radiation of furnace wall, so that the thermal efficiency of furnace can be improved [2]. erefore, scholars have proposed the concept of blackbody technology. e socalled blackbody technology refers to the industrial standard blackbody element, called the intermediate heat carrier in furnace, which integrates three functions of “enlarging furnace area, increasing furnace emissivity, and increasing irradiance” by using certain materials and processing technology according to the blackbody theory of infrared physics
A one-zone quaternary system model in the furnace with an intermediate heat carrier is established to derive the impact of length, position, and emissivity of the heat carrier on heat exchange capacity of the billet surface, and a conclusion by comparing with the literature data is summarized
It can be seen that the longer the intermediate heat carrier located at the top of the furnace, the larger the heat exchange capacity on the billet surface
Summary
In order to reduce carbon dioxide emissions from iron and steel enterprises and improve the thermal efficiency of heating furnace, increasing radiation from furnace wall is an effective method that needs more attention [1]. e thermal efficiency of heating furnace depends on many factors, among which, the appropriate shape of furnace can maximize the radiation of furnace wall, so that the thermal efficiency of furnace can be improved [2]. erefore, scholars have proposed the concept of blackbody technology. e socalled blackbody technology refers to the industrial standard blackbody element, called the intermediate heat carrier in furnace, which integrates three functions of “enlarging furnace area, increasing furnace emissivity, and increasing irradiance” by using certain materials and processing technology according to the blackbody theory of infrared physics. On the basis of the heating furnace with nongray radiation characteristics of furnace gas established by Yi et al [1], an intermediate heat carrier was added to the furnace, and a mathematical analytic formula of heat exchange capacity on the surface of billet was derived. Based on this mathematical analytic formula, the impact of different parameters on heat transfer in the furnace was analyzed
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