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Show 2. A muffle type continuous heat treating furnace Fig.2 shows the typical muffle type continuous heat treating furnace for the bnght-annealing process of a steel strip. The furnace is cylindrical and tall, roughly 30 m long. The furnace consists of combustion and reducing zones divided by a muffle to bright-anneal a steel strip in the reducing zone. A number of burners are installed along the furnace side wall to generate flames in the combustion zone. Flues are located around the bottom of the furnace. The reducing zone is filled up with a reducing gas such as H2. A steel strip is continuously charged into the reducing zone from the bottom of the furnace and discharged from the top. The steel strip is bright-annealed while transported through the reducing zone. The muffle, made of steels, needs to be heated uniformly to avoid serious thermal damage and maintain high quality of the products. The uniform heat transfer to the muffle is a matter of great importance for the bright-annealing process. To achieve it, the FDI regenerative burner system, which is proven to create a uniform heat transfer profile in steel reheating furnaces'4', has been applied to the muffle type furnace. When designing furnaces with the FDI regenerative burner system, a number of design parameters specific to the system need to be taken into account. The following sections describe a 3-dimensional detailed numerical analysis to predict the performance of the furnace and optimize the location of FDI regenerative burners. 3. Mathematical Model The commercial computer codes CFDS-FLOW3D and CFDS-RAD3D were used to solve turbulent transport and radiative heat transfer equations. The following equations were used. Fluid Flow Equation 1) Mass conservation equation V-(pC/) = 0 (1) 2) Momentum equation V(pUU)-V(^/rVU) = Vp'+V(v<ff(VU)r) (2) P' = p + 2l3(pk) + (2l3neJr-OVU (3) 3) k- E model of turbulence V-(pUk)-V-((jl+(jJbl Gk))Vk) = G-pe (4) V (pUe)-V>{{p+(ikl o*))Ve) = Cx{Elk)G-Cip{el Ik) (5) G = /UeffVU-(VU + (VU)T)-2l3-VU(^ieffVU + pk) (6) fleff = fJ. + jJi = fd + Cupk2 I £ (7) 3 |
