## 5 Results and Discussion
### Experimental Results  
The experimental results, as tabulated in Tables 6-8, indicate that the heat sinks of TTFHS, PTFHS, and MFLHS with LED at Reynolds number 14,916 exhibited higher heat transfer coefficients (\(h\)), and therefore, higher Nusselt number (\(Nu\)), and lower thermal resistance (\(R\)) than that at Reynolds number 6594. From experimental results, PTFHS exhibited the highest heat dissipation performance, followed by MFLHS and TTFHS because of the higher heat transfer coefficients and Nusselt number and lower thermal resistance and the increased surface area caused by perforations and the generated turbulent flow. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Case** & **Type** & \(\mathbf{T_{\text{sp}}}\) & \(\mathbf{T_{\text{b}}}\) & \(\mathbf{T_{\text{hs}}}\) & \(\mathbf{T_{\text{jet}}}\) & \(\mathbf{D}\) & \(\mathbf{A_{\text{b}}}\) & \(\mathbf{h}\) & \(\mathbf{N_{\text{sp-jet}}}\) \\  & & (\(\lx@math@degree\)C) & (\(\lx@math@degree\)C) & (\(\lx@math@degree\)C) & (\(\lx@math@degree\)C) & (\(\lx@math@degree\)C) & (m) & (\(\lx@math@degree\)C) & (\(\text{W m}^{-2}\text{k}^{-1}\)) & & (\(\text{K W}^{-1}\)) \\ \hline
1 & TTFHS & 39.1 & 32.8 & 30.8 & 25.0 & 0.038 & 0.00132 & 728.298 & 1068.545 & 1.88 \\
2 & PTFHS & 33.7 & 32.0 & 29.1 & 25.0 & 0.038 & 0.00132 & 811.532 & 1190.665 & 1.16 \\
3 & MFLHS & 37.6 & 32.2 & 29.0 & 25.0 & 0.038 & 0.00132 & 788.989 & 1157.591 & 1.68 \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Experimental validation results of cases 1–3 for TTFHS, PTFHS, and MFLHS with LED under inlet velocity of 6.13 m s\({}^{-1}\), Re = 14916. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Case** & **Type** & \(\mathbf{T_{\text{sp}}}\) & \(\mathbf{T_{\text{b}}}\) & \(\mathbf{T_{\text{hs}}}\) & \(\mathbf{T_{\text{jet}}}\) & \(\mathbf{D}\) & \(\mathbf{A_{\text{b}}}\) & \(\mathbf{h}\) & \(\mathbf{N_{\text{sp-jet}}}\) \\  & & (\(\lx@math@degree\)C) & (\(\lx@math@degree\)C) & (\(\lx@math@degree\)C) & (\(\lx@math@degree\)C) & (\(\lx@math@degree\)C) & (m) & (\(\lx@math@degree\)C) & (\(\text{W m}^{-2}\text{k}^{-1}\)) & & (\(\text{K W}^{-1}\)) \\ \hline
4 & TTFHS & 39.6 & 38.5 & 33.0 & 25.0 & 0.038 & 0.00132 & 420.794 & 633.275 & 1.95 \\
5 & PTFHS & 38.8 & 36.1 & 33.5 & 25.0 & 0.038 & 0.00132 & 511.777 & 770.199 & 1.84 \\
6 & MFLHS & 39.4 & 37.5 & 32.4 & 25.0 & 0.038 & 0.00132 & 454.458 & 683.937 & 1.92 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Experimental validation results of cases 4–6 for TTFHS, PTFHS, and MFLHS with LED under inlet velocity of 2.71 m s\({}^{-1}\), Re = 6594. Figure 8a-f provides the temperature profiles of the experimental results for the temperature distribution at the \(T_{\rm SP}\), \(T_{\rm b}\), and \(T_{\rm hs}\) points, as well as the calculation of \(T_{\rm j}\) for cases 1-3 and cases 4-6, respectively. Figure 8g-i provides the temperature profiles of the experimental results for the temperature distribution at the \(T_{\rm SP}\), \(T_{\rm b}\), \(T_{\rm hs}\), and \(T_{\rm trim}\) points, as well as the calculation of \(T_{\rm j}\) for cases 7-9. The steady-state temperature for each case is presented in Tables 6-8. As depicted in Figure 8a-i, the transient response of temperature rise under jet impingement cooling is fast and reaches the steady state for the first 25 min after powering on. The test duration time was 120 min. Each heat sink in different conditions exhibits various temperature distributions, such as comparisons between cases 1 and 4, or cases 2 and 5, or cases 3 and 6. The results indicate that a higher Reynolds number results in lower \(T_{\rm sp}\). Moreover, comparing between cases 1 and 7, or cases 2 and 8, or cases 3 and 9, the results indicate that the heat sink with housing exhibited increased \(T_{\rm sp}\) because the thermal resistance increased due to their longer heat dissipation paths. In cases 7-9, \(T_{\rm trim}\) was lower than \(T_{\rm sp}\) because of the thermal resistance.