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Show (4) Stored heat Fig. 9 shows the stored heat calculated at varying wall thicknesses of the honeycomb from 0.5 to 5 mm, where the heat transfer surface area is unchanged. Note that the numbers indicate the changeover time. The figure obviously tells the stored heat increases in proportion to the increase in wall thickness if the changeover time is infinite. However, if the changeover time is short, as you can see from the figure, the relationship is not always proportional. The reason for this is that since in the wall thickness simulation model the heat' transfer from the outside surface to the inside su~face of the wall requires a certain amount of time, the short changeover time generates a large temperature difference between the outside and inside surfaces. In this study, we concluded that there is a certain relationship between the wall thickness and the changeover time. 3. Running Test of the Regenerative Burner System at NKK Keihin Works 3-1 Test facility 3-1-1 Test furnace We installed a regenerative burner system at the top of zone 1 at the inlet side of bright annealing furnace No. 4 located in the cold drawing pipe mill of NKK Keihin Works. The furnace was a non-oxide atmospheric heat treatment furnace. Strain is removed from the seamless tube drawn at an room temperature by annealing. Table 3 lists the specifications for the bright annealing furnace No.4. Fig. 10 show the bright annealing furnace No.4 schematically. 3-1-2 Test burner (1) Burner setup configuration Fig. 11 shows a flow chart of the burner system. Table 4 shows the standard specification of the test burner. In the regenerative radiant tube burner system, burners are installed to both ends of the radiant tube as shown in Fig. 13. The respective burners have regenerator media to fire alternately at a changeover interval of 60 seconds. The regenerator media in the firing side acts as a hot air generator (heat source) while the media on the non-firing side stores the heat. The introduction of honeycomb ceramic allows the regenerator media to provide hot air at very high temperature (approximately 800 °C) and to decrease the exhaust gas temperature drastically compared to the conventional burner system. The flaming burner is changed by the four-way changeover valve. (2) Operation of the test burner Fig. 12 shows the time chart for the sequence of the burner control after it is ignited. The following descriptions provide a rough operating sequence for the burner: Upon receiving the changeover signal, the four-way changeover valve requires 3 seconds to select the burner to be ignited. Then~ the fuel and air supply solenoid valve is opened for the pilot burner, and the pilot burner is ignited by the ignition system. Five seconds after the pilot burner solenoid valve is opened, the main burner's fuel changeover valve (solenoid valve) is opened to start the combustion. The solenoid valve for adding steam is opened simultaneously with the pilot burner solenoid valve. These operations' are executed alternately on burners A and B. - 5 - |