# Impact of Temperature on the Moisture Buffering Performance of Palm and Sunflower Concretes
## 3 Model Validation
### Model Validation  
In order to validate the numerical model presented above, the numerical results obtained were compared with experimental ones found in the literature [13] carried out on a single-layer wall of palm concrete with a thickness of 9.5 cm. The experimental studies were performed by [PERSON] et al. 2018 [13] to determine the values of the MBV at different temperatures, 10 \({}^{\circ}\)C and 23 \({}^{\circ}\)C. During the tests, the samples were conditioned \begin{table}
\begin{tabular}{c c c} \hline \hline
**Materials** & **PC** & **SC** \\ \hline \(w_{m}\) & 0.019 & 0.0171 \\ \hline \(C\) & 1 & 27 \\ \hline \(K\) & 0.86 & 0.76 \\ \hline \(R^{-2}\) & 0.98 & 0.99 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Fitting parameters of GAB model. Figure 1: Sorption isotherm curves of the studied concretes. beforehand at a relative humidity of 50% and were exposed to a constant temperature, while the RH was varied according to a square wave signal RH (t) having an adsorption phase of 8 h at 75% RH, followed by a desorption phase of 16 h at 33% RH. More details about the tests and experimental setup can be found in [13]. The experimental values of the moisture buffering capacity obtained according to the experimental protocol recommended in NordTest [7] are grouped in Table 2.  
This numerical study aims to determine the moisture buffer capacity of palm concrete at two different temperatures, 10 \({}^{\circ}\)C and 23 \({}^{\circ}\)C, and then to compare with the experimental results. The boundary conditions of the simulation are defined by a single face of the wall which is permeable to water vapor, and the other faces are considered impermeable, as presented in Figure 2. Note that these simulation conditions are similar to experimental ones carried out in [13]. The interior convective mass transfer coefficient h\({}_{\text{M,i}}\) is 0.002 m\(\cdot\)s\({}^{-1}\). Concerning the interior RH variation, it was chosen according to the NordTest protocol [7] as mentioned in [13]; however, the temperatures for the two tests were fixed at 10 \({}^{\circ}\)C and 23 \({}^{\circ}\)C, respectively, to study the impact of T on the MBV. The MBV was calculated at the equilibrium state using the following equation:  
\[\text{MBV}=\frac{\Delta m}{S(\text{RH}_{\text{max}}-\text{RH}_{\text{min}})} \tag{9}\]  
where \(\Delta m\) is the change in mass of the sample at the equilibrium state (kg), RH\({}_{\text{min}}\) and RH\({}_{\text{max}}\) are the minimum and the maximum relative humidity (% RH), respectively, and \(S\) is the exposed surface area (m\({}^{2}\)). \begin{table}
\begin{tabular}{c c c} \hline \hline
**Hygrothermal Properties** & **PC** & **SC** \\ \hline Density \(\rho\) (kg/m\({}^{3}\)) & 954 & 539.64 \\ \hline Total porosity & 64\% & 70\% \\ \hline Open porosity & 58\% & 68.6\% \\ \hline Thermal conductivity \(\lambda\) (W/(m\(\cdot\)K)) & 0.185 & 0.127 \\ \hline Specific heat capacity C\({}_{\text{p}}\) (J/(kg\(\cdot\)K)) & 1500 & - \\ \hline Water vapor diffusion resistance factor \(\mu\) & 5.57 & 2.62 \\ \hline MBV measured at 23 \({}^{\circ}\)C & 2.96 & 2.26 \\ (g/(m\({}^{2}\)\(\%\)RH)) & & \\ \hline MBV measured at 10 \({}^{\circ}\)C & 2.03 & - \\ (g/m\({}^{2}\)\(\%\)RH)) & & \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Hygrothermal properties and measured MBV of studied bio-based concretes [13; 14]. Figure 2: Studied configuration at single-layer wall scale. Regarding the numerical solution, the simulation time step was set to 240 s, and the wall thickness was discretized into 50 nodes. The hygrothermal properties used for the simulation are presented in Figure 1 and Table 2.  
The numerical results obtained are the mass variation curves at the equilibrium state of the palm concrete at different temperatures, 10 \({}^{\circ}\)C and 23 \({}^{\circ}\)C. They are then compared to the ones obtained experimentally by [PERSON] et al. (2018) ([PERSON] et al., 2018), which are shown in Figures 3 and 4.