## 3 Results  
In order to carry out reliable simulation work, the size of the mesh element was selected at the outset, and it was performed in such a way as to achieve convergence of results. The duration of the simulation was also recorded. The results obtained are presented in Table 1. As a representative point, an octagonal surface above the diode thread was selected. Obtaining correct temperature distributions required the selection of correct values for the convection coefficients. This was conducted using Equations (7)-(13). The observed surface was oriented perpendicular to the direction of air flow. It was the rear surface of the solid that was hit by airflow. For this reason, the equations for turbulent flow were chosen. The selected materials, as well as the convection and thermal conductivity coefficients, are summarized in Table 2. \begin{table}
\begin{tabular}{c c c c} \hline
**Mesh Element Size (mm)** & \(T_{\text{sym}}\) (\({}^{\circ}\)**C**) & \(T_{\text{c}}\) (\({}^{\circ}\)**C**) & **Duration of the Simulation (s)** \\ \hline
1.0 & 63.2 & 64.5 & 980 \\
2.5 & 63.1 & 64.5 & 280 \\
5.0 & 51.5 & 64.5 & 12 \\ \hline \end{tabular}
\end{table} 
Table 1: The dependence of the convergence of the result and the simulation duration on the size of the mesh element. \begin{table}
\begin{tabular}{c c c} \hline
**No.** & **Material** & \(k\) **(W/(m\(\cdot\)K))** \\ \hline
1 & Cast steel & 80 \\
2 & Cast steel & 80 \\
3 & Aluminum & 100 \\
4 & Epoxy & 0.2 \\
5 & Aluminum & 100 \\
6 & Silicon & 150 \\
7 & Aluminum & 100 \\
8 & Aluminum & 100 \\
9 & Copper & 400 \\
10 & Aluminum & 100 \\
11 & Porcelain & 2.5 \\ \hline \end{tabular} Points referenced in Table 2 are shown in Figure 6.  
\end{table} 
Table 2: Assigned material and selected values for the convection coefficients \(h_{c}/h_{c^{\prime}}\) (-) and the thermal conductivity coefficients \(k\) (W/(m\(\cdot\)K)). The \(k\)-factor values were assigned to the selected materials by the software manufacturer. Figure 6: Points with assigned properties, described in Table 2.  
Using the test rig presented in Figure 4, thermograms were taken, as shown in Figure 7. Pj powers of 46.23 W, 74.48 W, and 111.75 W were dissipated at the diode junction. For each power, measurements were taken at air speeds of 0.75 m/s, 1 m/s, and 1.5 m/s. The thermograms are presented in Figure 7.  
The temperature distributions obtained from the simulation work are shown in Figure 8.  
The values of the convection coefficient for the cylinder \(h_{cr}\) and the convection coefficient for the flat surface \(h_{\mathcal{G}}\) for different values of \(P_{j}\) and \(v\) used in the simulation are presented in Tables 3-5. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**The Number of the Measuring Point**} & \multicolumn{2}{c}{\(h_{\mathcal{G}}\), \(h_{\mathcal{G}}\) [W/(m\({}^{2}\)K)]} \\ \cline{2-3}  & \(v\) = 0.75 m/s & \(v\) = 1.00 m/s & \(v\) = 1.50 m/s \\ \hline
3 & 63.2 & 64.5 & 980 \\
4 & 63.1 & 64.5 & 280 \\
5 & 51.5 & 64.5 & 12 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The values of the convection coefficient for the cylinder \(h_{cr}\) and the convection coefficient for the flat surface \(h_{\mathcal{G}}\) used in the simulation for \(v\) = 0.75 m/s, \(v\) = 1 m/s, and \(v\) = 1.5 m/s; when the value of the power dissipated at the junction, _Pj_ was 46.23 W (as marked in Figure 5). \begin{table}
\begin{tabular}{c c c c c c c} \hline
**No.