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Heating Effectiveness of an Industrial Furnace

A common process to treat raw steel billets is to heat the billets to a certain temperature in a gas fired furnace. During the heat treatment process, natural gas is blown into the furnace through several nozzles and ignited. The billets must reach the designated temperature (1100°C) within a certain amount of time, and the variation in temperature within each billet must be limited to a narrow range (50°C). Indeed, the furnace’s heating effectiveness is based on the uniformity of temperature reached within the billets. The positions of the nozzles and the lengths of the gas flames directly affect the heating effectiveness of the furnace.

In this News, we show how ADINA can be used to study the effects of the nozzle positions and flame lengths to guide the furnace design*. A thermal fluid-structure interaction (TFSI) analysis is performed, since the thermal expansion of the billets changes the boundary conditions of the turbulent gas flow, which in turn affects the flow and the heat transfer. In this simulation, conjugate heat transfer, fluid flow, and mechanical deformations are all coupled together.

Figure 1 shows the furnace and the billets. The furnace has 3 main nozzles at the top, and 2 auxiliary nozzles at the side. The flame lengths are controlled by the gas flow rates through the nozzles, and the flow rate can be different for each nozzle.





Figure 1  Furnace and billets with the 5 nozzle positions shown

In the ADINA simulation, the gas flow rates are specified by prescribing the velocities at the end of the nozzles. The turbulent gas fluid flow is simulated using the K-ε turbulence model. Figure 2 shows parts of the fluid and solid meshes of the furnace and billets. The nozzle positions and the flow rates are parameterized in the ADINA command input file allowing different nozzle positions and flame lengths to be easily constructed.





Figure 2  Parts of fluid and solid meshes of the furnace gas and billets


Figure 3 shows, at a particular time, the temperature of the billets and the above movie shows the temperature in the furnace gas. Figure 4 gives the flame lengths in the 3 main nozzles at the top of the furnace, where the flame length is determined by only plotting temperatures above 1350°C.






Figure 3  Temperature of the billets






Figure 4  Flame lengths




As an example, considering key locations in the billets, Figure 5 shows how the nozzle positions and the flame lengths significantly affect the temperature at these locations. In this figure, results for two different configurations of nozzle positions and flow rates are shown, where the distance is from the key locations to the centre of the left hand side of the furnace. These curves provide important insight for a furnace design and the billet treatment process.






Figure 5  Effect of nozzle position and flame length on the billet temperature




With the analysis capabilities available in ADINA, many important multiphysics coupling effects can be included in simulations. Using these capabilities, not only can the interaction between a wide range of different physical fields be accounted for, but each of these fields is treated in a general form without compromising on the solution accuracy.

This News demonstrates how the powerful multiphysics capabilities in ADINA can be used to optimize complex manufacturing processes and industrial designs.

 


Keywords:
Furnaces, conjugate heat transfer, thermal fluid-structure interaction (TFSI), multiphysics, model parameterization, design sensitivity analysis


*Courtesy of Radux Industry Technologies, Inc., Beijing, China

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