## 3 Results
### Variation in Nusselt Number with Re  
.1.1 Comparison of Experimental Results for Inclined Heat Sink (\(\alpha\) = 10\({}^{\circ}\))  
For the rectangular, finned heat sink inclined at 10\({}^{\circ}\), the Nu increased with increasing Re. An increase in the nozzle diameter and jet air velocity also contributed to higher Nus. Conversely, the Nu increased with a decreasing h/d ratio, with the relationship being largely linear. The variations in Nus with Res for dimensionless distances (h/d = 6, 7, 8) are presented in Figures 3-5. Figure 3: Comparison of experimental results for inclined heat sink (\(\alpha\) = 10\({}^{\circ}\)) at constant heat flux (200 W) and h/d = 6. \begin{table}
\begin{tabular}{l l} \hline
**Variable** & **Uncertainty (\%)** \\ \hline Velocity of fluid (U) & 5 \\ Mean temperature (T) & 0.25 \\ Diameter of the nozzle (D\({}_{\mathrm{h}}\)) & 0.1 \\ Voltage (V) & 0.1 \\ Current (I) & 0.72 \\ Dynamic viscosity of the air (\(\mu\)) (from tables) & 0.048 \\ Thermal conductivity of the air (k) (from tables) & 0.34 \\ Density of the air (\(\rho\)) (from tables) & 0.008 \\ \hline \end{tabular}
\end{table} 
Table 5: Uncertainties for the values of the relevant variables. The experimental results of the Nu-Re variation for five different velocity values, considering a rectangular, finned, 10\({}^{\circ}\) inclined heat receiver at a constant heat flux of 200 W, under different nozzle-to-heat sink distances (normalized by nozzle diameter) and nozzle diameters, are presented in Figure 3. Considering the experimental results, it was observed that the Nu increased with the rising Re and nozzle diameter. Conversely, it was determined that the Nu increased as the dimensionless h/d distance decreased, and this relationship was predominantly linear. While the Nu was similarly affected across all jet velocity levels, it exhibited a more significant impact at higher speeds, particularly around 7 m/s, compared to lower velocities. For all nozzle diameters and nozzle-to-heat sink distances normalized by the nozzle diameter, the Nu reached its maximum value at the highest flow speed (9.0 m/s). At a constant heat flux, the highest Nu for the rectangular, finned, 10\({}^{\circ}\) inclined heat receiver was calculated for a nozzle diameter of D = 40 mm, at a distance of h/d = 6, and a flow velocity of 9 m/s. For a constant heat flux, at a nozzle diameter of D = 25 mm and a distance of h/d = 6, the Nu of the rectangular finned, 10\({}^{\circ}\) inclined heat sink showed an increase in the range of 6-10% between consecutive velocity increments. Furthermore, under the same conditions, an increase of 36.8% for the Nu was found between the minimum (4.0 m/s) and maximum (9.0 m/s) velocities. For a nozzle diameter of D = 32 mm at h/d = 6, the increase in the Nu was between 2% and 8% for consecutive velocity increments, with a total increase of 19.8% between the minimum and maximum velocities. Similarly, for a nozzle diameter of D = 32 mm, the Nu was found to be less than 10\({}^{\circ}\) inclined heat sink. Figure 4: Comparison of experimental results for inclined heat sink (\(\alpha\) = 10\({}^{\circ}\)) at constant heat flux (200 W) and h/d = 7. Figure 5: Comparison of experimental results for inclined heat sink (\(\alpha\) = 10\({}^{\circ}\)) at constant heat flux (200 W) and h/d = 8. D = 40 mm at h/d = 6, the Nu showed an increase of 2.7-7% between consecutive velocity increments and a total increase of 21.1% between the minimum and maximum velocities. According to the experimental results for the constant heat flux (200 W) and inclined heat sink (\(\alpha\) = 10\({}^{\circ}\)) at h/d = 6, it was observed that the heat transfer was enhanced as the fluid velocity and nozzle diameter increased. For h/d = 7, with a nozzle diameter of D = 25 mm, the Nu exhibited a rise of 6.4-10.9% between consecutive velocities and a total increase of 41.6% between the minimum and maximum velocities. For D = 32 mm, the corresponding increases were 4.5-7.2% between consecutive velocities and 24.1% between the minimum and maximum velocities.