# Numerical Analysis on the Performance of a Radiant Cooling Panel with Serpentine-Based Design
## 3 Results and Discussions
### CFD Simulation--ANSYS Fluent
#### 3.3.2 Temperature Distribution  
Table 8 shows the minimum and maximum temperatures of the panel's surface, with its mean panel temperature as calculated by Ansys Fluent. Based on Table 8, Design 2 has the lowest mean panel temperature, indicating that the temperature distribution in Design 2 has the most uniformity. The common serpentine flow configuration in Design 1 has the highest mean panel temperature, with a 298.919 K maximum panel temperature and a 293.441 K minimum panel temperature. Based on the panel's surface temperature, shown in Table 8, Design 1 is not as good as the other two designs in respect of obtaining uniform temperature distribution. This is because the water flowing inside the tube becomes hotter with the increasing length, thus decreasing the heat absorption performance, resulting in a higher panel temperature at the area around the water outlet. This phenomenon can be seen from the temperature contour shown in Figure 9, where the edge of the panel surface located at the water outlet has a higher temperature compared to the panel surface located near the water inlet. The concentration of the cold region can be seen clearly at the water inlet, with temperature increases along the pipe length. This temperature contour agrees with [PERSON] et al. [1] showing a similar temperature distribution characteristic. In the case of Design 2, the cold region is concentrated in the middle part of the RCP. This is because the water inlets are located next to each other, thus creating a very low minimum panel surface temperature at that region. In addition, the temperature contour for Design 2 shows a uniform temperature distribution throughout the panel's surface \begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Design**} & \multicolumn{2}{c}{**Maximum Outlet Water**} & \multicolumn{2}{c}{**Temperature Difference**} & \multicolumn{1}{c}{**Total Heat**} \\  & **Temperature, (K)** & **(T\({}_{\text{inlet}}\)-T\({}_{\text{outlet}}\)), (K)** & **Transfer Rate (W)** \\ \hline
1 & Outlet 1 & 291.659 & 3.659 & 23.122 \\ \hline \multirow{2}{*}{2} & Outlet 1 & 289.716 & 1.716 & \multirow{2}{*}{28.111} \\  & Outlet 2 & 289.727 & 1.727 & & \\ \hline \multirow{3}{*}{3} & Outlet 1 & 289.476 & 1.476 & \multirow{3}{*}{26.247} \\  & Outlet 2 & 288.822 & 0.822 & & \\ \cline{1-1}  & Outlet 3 & 289.417 & 1.417 & & \\ \hline \end{tabular}
\end{table} 
Table 7: Maximum outlet water temperature and total heat transfer rate. \begin{table}
\begin{tabular}{c c c c} \hline \multirow{2}{*}{**Design**} & \multicolumn{2}{c}{**Minimum Panel**} & \multicolumn{2}{c}{**Maximum Panel**} & \multicolumn{1}{c}{**Mean Panel**} \\  & **Temperature (K)** & **Temperature (K)** & **Temperature (K)** \\ \hline
1 & 293.441 & 298.919 & 295.533 \\
2 & 291.206 & 295.711 & 293.368 \\
3 & 291.626 & 296.801 & 293.943 \\ \hline \end{tabular}
\end{table} 
Table 8: Radiant cooling panel surface temperature. compared to those of Design 1 and Design 3. There is a smaller greenish region observed in the temperature contours of both Design 1 and Design 3. What is more, the greenish region that represents a relatively low-temperature zone is not evenly spread throughout the panel's surface in both Design 1 and Design 3. The middle pipe has no significant impact on the cooling performance of the RCP in Design 3, and the cold region is only concentrated at the right side of the panel's surface where the water inlet is located. The left side of the panel's surface, where the water outlets are placed near each other, shows an increase in temperature due to the increase of water temperature being concentrated in that region. For all three designs, the tubes did not cover the edges of the plate, resulting in a hotter region compared to the rest of the surface [1]. This is because the chilled water has less access to the surface of those regions [1]. To gain more understanding of the temperature distribution of the panel's surface, a temperature distribution graph is plotted by dividing the plate into three equally spaced segments.