## 2 Experimental Setup
Figure 3: Location of the thermocouples mounted on (**a**) the upper surface of the cover, (**b**) the upper surface of the PCM package, (**c**) the lower surface of the PCM package, with (**d**) an overview of the mounted thermocouples (all dimensions are given in mm). The main selection criterion for PCMs for this study was their melting temperatures. [PERSON] et al. [36] showed numerically that PCMs with melting points between 35 and 41 \({}^{\circ}\)C provide very good transient performance by nearly fully melting during 30 min of operation. Based on these numerical studies, two PCMs were selected: \(n\)-eicosane (technical grade paraffin) and dodecanoic acid, a fatty acid. Table 2 summarizes the physical properties of both PCMs. Those two PCMs have similar physical properties but different melting points. Hence, they allow an investigation of the influence of different melting temperatures on the performance. These materials were chosen since they are nontoxic, and do not show any corrosive effects when in contact with aluminum. Furthermore, these materials have been used in many research projects, their physical properties are measured and their long-term stability has been proven in previous work for up to 4000 melt-freeze cycles [37; 38]. Both values of the properties and the uncertainties listed in Table 2 are adopted from these publications. Two PCM packages were fabricated from two \(120\times 120\) mm aluminized films, which were heat sealed along a 10-mm border. The pocket therefore had dimensions of approximately \(100\times 100\times 2\) mm filled with PCM. A mold consisting of two parallel plane aluminum sheets separated by a distance of 2 mm was used for filling of the PCM packages. The empty packages were sealed on each side except for the top and mounted into the 2-mm gap of the mold. This was then placed into a water bath (temperature between 45 and 50 \({}^{\circ}\)C) and the liquid PCM was inserted into the package using a syringe. Once filled, the top seam was sealed. The filling mass and the type of PCM used in the packages are summarized in Table 3. Table 3 also shows the latent storage capacity of both PCM packages, as well as the total storage capacity (latent plus sensible taken over a 50 \({}^{\circ}\)C temperature increase, which is representative of the order of magnitude observed in the experiments) for both packages. Although \(n\)-eicosane has a larger latent heat, with its higher heat capacity, dodecanoic acid ends up storing approximately the same amount of energy over a 50 \({}^{\circ}\)C temperature increase (that includes melting). Heat-sealable aluminized film (Marvelseal 360, Class 1) was used to encapsulate the PCM. This film is composed of a thin aluminum layer sandwiched between a nylon and a polyethylene layer, having a total thickness of 0.132 mm. A thin square aluminum (thermal conductivity of 167 W/m\(\cdot\)K) sheet (100 \(\times\) 100 \(\times\) 0.4 mm) was used as a thermal spreader. The side length of the thermal spreader (100 mm) is identical to the side length of the square filled PCM package. \begin{table}
\begin{tabular}{c c c c} \hline
**Properties** & **\(n\)-eicosane**[10; 38] & **Dodecanoic Acid**[37] \\ \hline \(T_{m}\) (\({}^{\circ}\)C) & 35.6 & 43 \(\pm\) 1.5 \\ \(\rho_{s}\) (kg/m\({}^{3}\)) & 780 & 930 \(\pm\) 20 \\ \(\rho_{l}\) (kg/m\({}^{3}\)) & 765 & 874 \\ \(C_{p,s}\) (J/g\(\cdot\)K) & 1.8 \(\pm\) 0.2 & 1.95 \(\pm\) 0.03 \\ \(C_{p,l}\) (J/g\(\cdot\)K) & 2.3 \(\pm\) 0.2 & 2.4 \(\pm\) 0.2 \\ \(k_{s}\) (W/m\(\cdot\)K) & 0.46 \(\pm\) 0.05 & 0.150 \(\pm\) 0.004 \\ \(kl\) (W/m\(\cdot\)K) & 0.015 \(\pm\) 0.05 & 0.170 \(\pm\) 0.004 \\ \(\Delta t_{\mathit{flas}}\) (J/g) & 239 \(\pm\) 24 & 184 \(\pm\) 9 \\ \hline \end{tabular}
\end{table} 
Table 2: Physical properties of the PCM used in the experiments.