The furnace fan is designed to create heat transfer agent circulation in the furnace working space, heated by calorifiers. (See Fig. 1). In Fig.2 the scheme of shaft furnace circulation circuit is presented.
The circulation circuit consists of the following elements: 1.Furnace fun 2. Heat-insulated furnace body 3.Processed material 4. Louver 5.Furnace heater unit 6.Heat transfer agent 7.Aerodynamically transparent stand.
The circulation circuit works as follows. The fan supplies the heat transfer agent to the channel of the furnace heaters, when the gas moves in the channel, an intense convective heat exchange occurs between the gas and the surface of the processed products, as well as between the gas and the surface of the heating elements. Further, the gas passes through an aerodynamically transparent stand and is supplied to the fan inlet, while convective heat exchange occurs between the gas and the internal surfaces of the processed products.
Calculations show that when a furnace fan is used as the mover of the heat transfer agent, it leads to an increase in the convective heat transfer coefficient on external surfaces of the processed products from 5-15W/m2×°Ñ to 30-40W/m2×°Ñ, on the internal surfaces from 5-15 W/m2×°Ñ to 35-45W/m2×°Ñ. At the same time, depending on the design of the heating elements, the convective heat transfer coefficient on their surfaces can increase from 10-25 W/m2×°Ñ to 50-60 W/m2× °Ñ as compared to no-fan construction.
High-speed blowing with a heat transfer agent (air) allows to increase the convective heat transfer coefficient on the processed products surfaces which makes their heating faster and more uniform, contributing to the furnace unit productivity.
In addition, during the fan operation the convective heat transfer coefficient on the heating elements of the calorifiers increases which reduces their operating temperature preventing possible local overheating and extending their service life.
The main specifications of furnace fan are the following:
• Furnace fan capacity up to 6000 m3/h;
• Total pressure under normal conditions up to 800 Pa;
• Maximum temperature of transmitted medium up to 400 C˚;
• Motor power 7.5 kW.
The design of the furnace fan uses advanced bearing assemblies with a shaft air-cooling system.