## 3 Results and Discussion
### Mixing Process Tracking
#### 3.1.3 Model Validation  
The validation of the model was carried out to determine its accuracy not only for the gas mixtures used to build it, but also for mixtures made with other concentration values too [53]. Five gas mixtures were proposed, different from the ones used to prepare the model. The composition of the gas mixtures is shown in Table 7.  
The concentration profiles of these mixtures were simulated. The \(D\) and \(K\) coefficients that were used for the binary mixtures are the ones shown in Table 5, and the \(D_{\textit{eff}}\) and \(K\) coefficients that were used for the ternary mixture are obtained from Table 6. The residuals of each mixture, throughout the whole experiment, were calculated:  
\[Residual=C_{exp}-C_{model}\left[\text{mol m}^{-3}\right] \tag{23}\]  
The mean residual value of all four measurement lines at a specific time (\(\overline{R_{t}}\)) and the mean residual value of a specific measurement line (\(\overline{R_{L}}\)) until the end of the experiment (\(t\)) were also calculated:  
\[\overline{R_{t}}=\frac{\sum_{t=1}^{4}\bigl{(}C_{exp}-C_{model}\bigr{)}_{L}}{4} \left[\text{mol m}^{-3}\right] \tag{24}\]  
\[\overline{R_{L}}=\frac{\sum_{t=0}^{t_{f}}\bigl{(}C_{exp}-C_{model}\bigr{)}_{t}} {N}\left[\text{mol m}^{-3}\right] \tag{25}\]  
The end of the experiment was considered when the concentration of the four lines reached stabilization. All the mean residual values were represented against \(C_{exp}\), including the mixtures that were used for building the model [53]. \(\overline{R_{t}}\) is represented against \(C_{exp}\) in Figure 10. The residuals of PFK5 do not show a distinct tendency; they are distributed almost evenly in the positive and negative sides of the \(y\)-axis and are near zero. This shows that the error of PFK5 is not carried over with the model. There is no significant difference between the \(\overline{R_{t}}\) of PFK5 of binary and ternary mixtures. The results for HFO3E show higher residual values and they are not evenly distributed. Most of them are negative values, which shows that the model is more likely to present higher values than the experimental ones. The residuals also decrease with time, so the model showed better results near stabilization. The low absorptivity of this component, together with the higher molar flow at the beginning of the experiments, makes it more difficult to predict the values of concentration. Besides, the concentration of HFO3E of the binary mixtures is easier to calculate as the residuals are lower. \(\overline{R_{L}}\) is represented against \(C_{exp}\) in Figure 11. Lines T and MB show lower residual values for both components. PFK5 clearly shows lower residual values in both binary and ternary mixtures. The values of HFO3E of the ternary mixtures are higher than the ones of the binary mixtures. The model will predict lower values than the experimental ones in line MT and higher ones in line B. Line B shows the highest absolute residual values, especially for HFO3E. The higher molar concentration and molar flux that was found in this line complicated the ability of the model to predict the concentration values. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Name** & \(C_{\textit{PFK5}}\) **(\%)** & \(C_{\textit{HFOO3E}}\) **(\%)** & \(C_{\textit{DRY,AIR}}\) **(\%)** \\ \hline B-5P & 5 & 0 & 95 \\ B-15P & 15 & 0 & 85 \\ B-15H & 0 & 15 & 85 \\ B-30H & 0 & 30 & 70 \\ T-20P/40H & 20 & 40 & 50 \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Nomenclature and concentration (C) of the components of the gas mixtures used for validation. Figure 11: Mean residual value of the measurement lines at all times (\(\overline{R_{L}}\)) of the mixing process. The results of all the binary (\(\Circle\) and \(\square\)) and ternary (\(\otimes\) and \(\boxtimes\)) mixtures are represented for PFK5 and HFO3E, respectively. Figure 10: Mean residual value of all measurement lines at different times (\(\overline{R_{t}}\)) of the mixing process.