## 2 Experimental Methods
### Reliability of Experimental Setup  
To verify the reliability and overall integrity of the experimental apparatus, tests were carried out on the Plain (polished) and Sintered Plain test pieces using de-ionized and de-gassed water. The experimental results were compared with the widely applicable and extensively used Stephan-Abdelsalam correlation [45] for nucleate pool boiling in water. Proposed in 1980, this empirical correlation requires no tuning parameters for nucleate pool boiling in water. Proposed in 1980, this empirical correlation requires no tuning parameters [46; 47; 48], contributing to its value and frequent citation [49; 50; 51]. Its adaptability and proven success in applied research underscore its significance in boiling heat transfer. The Stephan-Abdelsalam correlation for water on a plain surface is given by Equation (4) [45]. \[Nu=0.246\times 10^{7}\times\left(\frac{qd}{k_{l}T_{sat}}\right)^{0.673}\left( \frac{\Delta hd^{2}}{\chi_{l}^{2}}\right)^{-1.58}\left(\frac{c_{pl}T_{sat}d^{ 2}}{\chi_{l}^{2}}\right)^{1.26}\left(\frac{\rho_{l}-\rho_{p}}{\rho_{l}}\right) ^{5.22} \tag{10}\]  
where \begin{table}
\begin{tabular}{c c c} \hline
**Test Piece** & \(\mathbf{u_{q}}\) **[kW/m\({}^{2}\)]** & \(\mathbf{u_{h}}\) **[kW/m\({}^{2}\)**-K]** \\ \hline Plain & \(\pm 2.42\) & \(\pm 2.59\) \\ Sintered Plain & \(\pm 2.09\) & \(\pm 2.29\) \\ Small Lattice & \(\pm 6.10\) & \(\pm 6.19\) \\ Large Lattice & \(\pm 7.05\) & \(\pm 7.13\) \\ Staggered & \(\pm 0.93\) & \(\pm 1.32\) \\ \hline \end{tabular}
\end{table} 
Table 2: Calculated uncertainty analysis of the heat flux and heat transfer coefficient. \begin{tabular}{c c c} \(Nu\) & Nusselt number (dimensionless heat transfer coefficient) & \([-]\) \\ \(q\) & Heat flux & \(\left[\text{W}/\text{m}^{2}\right]\) \\ \(d\) & Bubble departure diameter & \([\text{m}]\) \\ \(k_{l}\) & Thermal conductivity of liquid & \([\text{W}/\text{m}\cdot\text{K}]\) \\ \(T_{sat}\) & Saturation temperature & \([\text{K}]\) \\ \(\Delta h\) & Latent heat & \([\text{J}/\text{kg}]\) \\ \(x_{l}\) & Thermal diffusivity of liquid & \([\text{m}^{2}/\text{s}]\) \\ \(c_{pl}\) & Specific heat of liquid at constant pressure & \([\text{kJ}/\text{kg}\cdot\text{K}]\) \\ \(\rho_{l}\) & Density of liquid & \([\text{kg}/\text{m}^{3}]\) \\ \(\rho_{v}\) & Density of vapor & \([\text{kg}/\text{m}^{3}]\) \\ \end{tabular}   
The correlation implicitly accounts for the type of fluid through its properties \(\left(\rho_{l}\), \(\rho_{\sigma}\), \(c_{pl}\), \(k_{l}\), and \(\Delta h\), \(\sigma\right)\) obtained from REFPROP steam tables. The experimental data provided \(q\), \(T_{sat}\), \(P_{sat}\) The bubble departure diameter (d) is crucial for the Stephan-Abdelsalam correlation and was calculated using Equation (5), as provided in the model [45]. \[d=0.0146\beta\left[\frac{2\sigma}{8\left(\rho_{l}-\rho_{v}\right)}\right]^{ \frac{1}{2}},\ \beta=0.45^{\circ}\ for\ water \tag{11}\]  
Experiments with the Plain and Sintered Plain test pieces were conducted under the same conditions to confirm repeatability. Figure 9 shows the results of the two similar experiments, which match well with the predictions from the [PERSON] and Abdelsalam correlation, confirming the reliability and integrity of the experimental apparatus. Thus, the experimental setup was well fabricated, and the results are considered trustworthy and repeatable. Therefore, the thermal resistance between the solid copper rod (Plain) and the additively manufactured copper rod (Sintered Plain) is considered negligible, and the results are analyzed accordingly. Important considerations for validation included the surface condition, since the Stephan-Abdelsalam correlation does not explicitly account for surface roughness. The surface of the Plain samples was polished to a mirror finish using abrasive paper of different sizes, followed by a rubbing compound, achieving a clean mirror shine surface.