## 2 Experimental Section  
Experimental testing of the phase-change process of lauric acid yielded results that were used to define the boundary conditions and validate the results of an equivalent CFD model of the system. All experimental tests were developed in an isolated tank in which the volume of PCM was placed and heated until the phase change occurred. Figure 1 shows the experimental facility that was designed for the experiments.  
A square base volume with sides 220 mm \(\times\) 220 mm and height 67 mm of PCM were tested, with thicknesses that are considered sufficient in solar panel applications [32]. The entire container was manufactured in vinyl ester resin (VER) with a thickness of 10 mm, making heat transmission through the walls negligible. An electrical resistance adhered to an aluminium plate laid on the top of the container was used as a heater, while a proportional-integral-derivative controller (PID) was used to regulate the temperature of the isothermal process (see Figure 1). The container was thermally insulated using extruded polystyrene (XPS) and K-FLEX ST of 19 mm [33] to minimize atmospheric heat loss. Additionally, all tests were performed in an adiabatic chamber (Figure 2).  
Figure 1: Experimental facility design for the study of the phase-change process on the volume of PCM. Dimensions are in mm.  
A small pipe connecting the PCM to the outside of the tank was installed in one of the corners of the top enclosure. The pipe had a dual purpose: to purge the air at filling and to allow the PCM to expand due to the decreased density during the melting process.  
Lauric acid (CAS 143-07-7), with a purity greater than 98% from the manufacturer Sigma-Aldrich (Saint Louis, United States) [34], was selected as the PCM. Its thermophysical properties are shown in Table 1.  
A total of 30 T-type thermocouples (uncertainty temperature, u(T) \(\pm\) 0.5 \({}^{\circ}\)C) were located inside the PCM on the same vertical plane, arranged in an array, separated from the sidewalls, and protected to prevent corrosion [35]. As shown in Figure 1, the thermocouple array was not regular since the tank had a plane of symmetry passing through column A. The thermocouple distribution was selected to obtain a regular and equivalent matrix by projecting columns B, D, and F onto the plane of symmetry. Together with the mentioned symmetry, this new equivalent matrix was used to simplify the simulated geometries. In Figure 1, red dots represent these thermocouples and Figure 2c shows the thermocouple array. Additionally, other thermocouples were placed for reference temperatures on the heated surface, bottom, container sides, and the outside. All data were  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Properties** & **Solid** & **Liquid** \\ \hline \(T_{Matcling}\) (K) & 316.65 & 321.35 \\ \(\rho\) (kg/m\({}^{3}\)) & 940 & 885 \\ \(C_{p}\) (J/kg K) & 2180 & 2390 \\ \(k\) (W/m\(\cdot\)K) & 0.16 & 0.14 \\ \(\mu\) (kg/m\(\cdot\)s) & 0.08 & 0.008 \\ \(\Gamma\) (K\({}^{-1}\)) & & 0.0008 \\ \(L\) (J/kg) & & 187210 \\ \hline \hline \end{tabular}
\end{table}
Table 1: Thermophysical properties of lauric acid. [25].  
Figure 2: (**a**) Experimental equipment; (**b**) position of the insulated PCM square tank in the adiabatic chamber; (**c**) array of thermocouples of the top enclosure.  
recorded every 15 s by a Campbell-Scientific CR1000 datalogger and a Campbell-Scientific AM16/32B multiplexer.