How is the integrated heat transfer in the muffle furnace?
In heat exchange, it is usually divided into at least three different temperature zones: furnace gas, furnace wall and heated (or melted) metal. Among them, the temperature of the furnace gas is the highest; the temperature of the furnace wall is the second; the temperature of the heated metal is the lowest. In this way, between the furnace and the furnace wall, between the furnace gas and the metal, and between the furnace wall and the metal, heat exchange is carried out in the form of radiation and convection, and there is heat loss due to the heat conduction of the furnace wall (the Heat loss also has a certain effect on the heat exchange in the furnace). Let's analyze the main heat transfer methods of the heated metal in the muffle furnace.
(1) Radiant heat transfer from furnace gas to metal After the heat radiated by the muffle furnace gas is transferred to the furnace wall and the metal surface, part of it is attracted and the other part is reflected back. The reflected heat must pass through the furnace gas that fills the furnace, part of it is absorbed by the furnace gas, and the remaining part is radiated to the opposite furnace wall or metal, and so on repeatedly.
(2) The radiation heat transfer of the furnace wall and roof to the metal. Its radiation situation is somewhat similar to the previous one, and it is also repeated radiation continuously. The difference is that the inner surface of the furnace wall also absorbs heat in a convective manner, and the heat is still transmitted in a radiant manner.
(3) Convective heat transfer of furnace gas to metal In the existing furnace of flame furnace, the temperature of furnace gas is mostly in the range of 800℃~1400℃. When the furnace gas temperature is around 800℃, the effects of radiation and convection are almost equal. When the furnace gas temperature is higher than 800°C, the convective heat transfer decreases, while the radiation heat transfer increases sharply. For example, when the temperature of the open-hearth furnace gas in a steel plant reaches about 1800°C, the radiation part has reached about 95% of the total heat transfer.
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