# The Heat Transfer Analysis of an Acting-type Heat Retention Panel used in a Hot Rolling Process
## 3 Results and Discussion  
### Traditional Passive Heat Retention Panel  
To validate the numerical models developed in this study, the results of the transfer bar for the traditional passive heat retention panel model were compared with the in-situ data provided by CSC, as shown in Table 2. The in-situ temperatures were obtained with R2 DT and FET tests by measuring the upper surfaces of the transfer bar when it was passing through the traditional passive heat retention panel. R2 DT is the abbreviation of the temperature detector near the roughing mills and FET is the abbreviation of the temperature detector near the finishing mills. Table 2 shows that the in-situ temperature of the head was 1097 \({}^{\circ}\)C as measured using the R2 DT, and the numerical temperature was 1092.78 \({}^{\circ}\)C. The deviation between the in-situ and the numerical temperature was approximately 0.38%. The in-situ temperature of the head was 1078 \({}^{\circ}\)C as measured using the FET, and the numerical temperature was 1068.24 \({}^{\circ}\)C. The deviation between the in-situ and the numerical  
Figure 7: Computational grid tests for the traditional passive heat retention panel model. temperature was approximately 0.91%. The in-situ temperature of the tail was 1081 \({}^{\circ}\)C as measured using the R2 DT, and the numerical temperature was 1061.55 \({}^{\circ}\)C. The deviation between the in-situ and the numerical temperature was approximately 1.79%. The in-situ temperature of the tail was 1013.33 \({}^{\circ}\)C using the FET, and the numerical temperature was 1002.58 \({}^{\circ}\)C. The deviation between the in-situ and the numerical temperature was approximately 1.06%. As mentioned above, the numerical temperature difference in the head and the tail was 65.66 \({}^{\circ}\)C, which is close to the in-situ temperature, 64.67 \({}^{\circ}\)C.  
Figure 8 displays the temperature distributions of the transfer bar of numerical results and in-situ data from CSC. After the head of the transfer bar entered the heat retention panel (at the position of 90.02 m), it slowed down to 5 m/s at 139.22 m and then slowed down again to 2 m/s at 151.37 m. The residence time inside the heat retention panel of the tail is increased as the running speed of the head is decreased. This speed difference causes a temperature drop of the tail is larger than the head of the transfer bar. Eventually, the temperature difference is generated when the head and the tail reach the FET position. Figure 9 shows the temperature contours of the traditional passive heat retention panel model. It is obvious that the temperature difference was generated after the transfer bar passed through the heat retention panel. The local temperature contours of the heat retention panel, rollers, and the insulation wool are presented in Figure 10. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**R2 DT**} & \multicolumn{3}{c}{**FET**} \\ \hline  & **Num. (\({}^{\circ}\)C)** & **In-Situ (\({}^{\circ}\)C)** & **Deviation (\%)** & **Num. (\({}^{\circ}\)C)** & **In-Situ (\({}^{\circ}\)C)** & **Deviation (\%)** \\ \hline Head & 1092.78 & 1097.00 & 0.38 & 1068.24 & 1078.00 & 0.91 \\ \hline Tail & 1061.55 & 1081.00 & 1.79 & 1002.58 & 1013.33 & 1.06 \\ \hline \(\Delta\)T & 31.23 & 16.00 & - & 65.66 & 64.67 & - \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison of the numerical data with the in-situ data for the upper surface of the transfer bar with the traditional passive heat retention panel. Figure 8: Comparison of the numerical data with the in-situ data for the upper surface and centerline-surface of the transfer bar with the traditional passive heat retention panel. Table 3 shows that the numerical temperatures of the outer and inner wall of the heat retention panel were 114 \({}^{\circ}\)C and 711 \({}^{\circ}\)C, respectively. In addition, the numerical temperatures of the upper and lower surface of the rollers were 622 \({}^{\circ}\)C and 238 \({}^{\circ}\)C, respectively.