| OCR Text |
Show for upper zone. After that, two-dimensional unsteady heat conduction equation (12) of a slab is solved under the condition that the cross section of the slab is divided into 24 x 50 and time marching step is 30 seconds. 4. Results and discussion 4.1 Definition of the " skid mark" 1 0 . 24 The definition of the "skid mark" is ^ 0 18 (A explained using Figure 5 (that is g 0.12 oO. 06 one of the examples). The upper £ 0 figure shows iso-thermal contour of the discharged slab. The horizontal axis shows the length of the slab. *1 5 00 v 1480 The vertical axis shows the ^ ti1460 1440 thickness of the slab. The numbers in this figure mean local J1420 temperature of the slab. Skid beam is located at x=0.84m in this example and two walking beams are located at x = 0 m and x=2m. It is 1max-i4y«JiM __ , r S^f"" ' f^^ Sk 3E_ id mark=69[K] i Tmin=1424[K]| 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 Length of the slab [m] Figure 5 Definition of the "skid mark" clear that the low temperature area is formed near the contact area between the slab and the skid beam. The lower figure shows the temperature distribution averaged across the thickness of the slab. In this paper, such a temperature distribution is called "averaged temperature across the thickness". The horizontal axis shows the length of the slab. The vertical axis shows the averaged temperature of the slab. W e define the "skid mark" as the temperature difference between the highest value and the lowest value. In this example, the "skid mark" is 69K ; the highest value is 1493K and the lowest is 1424K. 4.2 Without skid shift Figure 6 shows relationship between a skid beam position and a "skid mark" without a skid shift. The horizontal axis shows the position of the skid beam. The vertical axis shows the "skid mark". The best skid position to minimize the "skid mark" depends on the temperature profile of gas. In the case that the temperature profile of gas in the furnace is uniform ( type A ), the "skid mark" becomes minimum with the skid beam located at the center of the walking beams . In the case of type B and type C, the best skid position moves to the higher temperature side (see Figure 6). The "skid mark" does not depend on the absorption coefficients during 0.12 and 0.20 m 1 in this study. |
