## 4 Discussion
### Dryout and Replenishment  
The dryout occurs in all porous media studied but appears earlier and more frequently in sand-based media than in bronze media. Replenishment only occurs in sand media and is more pronounced in those saturated by a surfactant solution.  
The dryout process is progressive: the drying of the porous medium in contact with the heating plate occurs gradually. From the experimental results, several conditions of the dryout process concur, such as cessation of the saturation liquid displacement of the porous media to the tray, minimum saturation value of the porous medium, progressive elevation of the surface temperature of the heating plate in contact with the porous medium, and the maximum value of the vapor pressure in the two-phase zone.  
Table 7 includes the values of the magnitudes corresponding to the state of total dryout the maximum volume of liquid displaced to the tray (\(V_{dt}\)), maximum temperature reached by the surface of the plate in contact with the porous medium (\(T_{pl}\)), and maximum vapor pressure in the two-phase zone (\(Pv_{pl}\)). The time corresponding to the state of total dryout (\(t_{dr}\)) and the degree of saturation (\(S\)) have also been included.  
Regarding the phenomenon of replenishment, it occurs when total dryout is reached. Figure 18 shows the significant magnitudes in the phenomenon of dryout-replenishment corresponding to the porous media S+W in a time interval between the replenishment and the dryout.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Porous** & \(t_{dr}\) **(s)** & \(T_{pl}\) **(\({}^{\circ}\)C)** & \(V_{dt}\) **(cm\({}^{3}\))** & \(S\) **(\%)** & \(Pv_{df}\) **(Pa)** \\ \hline B+W & 6960 & 242 \(\pm\) 1 & 635 \(\pm\) 8 & 33 \(\pm\) 1 & 101,901 \(\pm\) 2 \\ B+DS & 7800 & 256 \(\pm\) 1 & 619 \(\pm\) 8 & 35 \(\pm\) 1 & 101,901 \(\pm\) 2 \\ S+W & 9300 & 115 \(\pm\) 1 & 1007 \(\pm\) 13 & \(\approx\) 0 & 97,766 \(\pm\) 2 \\ S+DS & 5580 & 114 \(\pm\) 1 & 896 \(\pm\) 12 & 11 \(\pm\) 1 & 97,765 \(\pm\) 2 \\ \hline \hline \end{tabular}
\end{table}
Table 7: Total dryout magnitudes.  
With regards to the influence of the vapor pressure, it is observed that once boiling occurs throughout the porous medium, the absolute pressure in the two-phase zone is \(1.023\leq p_{v}\leq 1.036\) bar. These limits represent an overpressure of \(0.009\leq\Delta p_{v}\leq 0.022\) bar, where the maximum value is measured in the piezometer 4 (0.022 \(\pm\) 0.001 bar), corresponding to a time prior to the dryout-replenishment in the S+DS porous medium. Figures 19 and 20 depict the correlations between three of the magnitudes that identify the dryout-replenishment phenomena.  
Figure 19: Plate temperature and pressure in the S+DS porous medium: \(z=3.364\) cm to the heating plate, piezometer 4.  
Figure 18: (**a**) Volume of liquid displaced to the tray (\(V_{dt}\)); (**b**) Effective vapor pressure at the plate-porous medium interface (\(Pv_{pl-mp}\)); (**c**) Surface temperature of the plate (\(T_{pl}\)), temperature of the porous medium in contact with the plate (\(T_{mp}\)) and the temperature of liquid in the tray (\(T_{cb}\)) of the S+W porous medium in a time interval between the replenishment and the dryout.