# Modeling Liquid Thermal Conductivity of Low-GWP Refrigerants Using Neural Networks
## 2 Data Analysis  
The experimental dataset of \(\lambda_{L}\) for low-GWP refrigerants reported by [PERSON] et al. [22] was updated by collecting experimental data presented recently in the literature. This updated dataset was determined by following the same procedure used in the previous study. After the literature survey, a critical fluid-by-fluid analysis and selection of the collected experimental values were carried out. In particular, the experimental data clearly beyond the common trend were rejected together with the measurements performed at reduced temperatures higher than 0.9.  
A dataset of 3404 experimental \(\lambda_{L}\) data for 7 halogenated alkene refrigerants was defined from the selection procedure. Details for the dataset are reported in Table 1. Figure 1 depicts the behaviors of the experimental data as a function of \(T_{r}\) and \(P_{r}\). This figure shows that \(\lambda_{L}\) of the analyzed refrigerants decreases with increasing temperature and increases with increasing pressure, although its effect is limited up to moderate pressures. In addition, Table 1 and Figure 1 show that the selected \(\lambda_{L}\) data were measured over wide ranges of liquid thermal conductivity, temperature, and pressure. The physical properties of the refrigerants used in this work are reported in Table 2, together with the references of the property sources.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Refrigerant** & **Number of Data** & **T Range** & **\(P\) Range** & \(\lambda_{L}\) Range & **Source** \\  & **of Data** & **K** & **MPa** & **W m\({}^{-1}\) K\({}^{-1}\)** & **Source** \\ \hline R1224 yd(Z) & 53 & 316.25–376.37 & 1.00–4.07 & 0.05379–0.06979 & [32] \\ R1233 zd(E) & 1132 & 203.56–393.22 & 0.18–66.62 & 0.05719–0.11991 & [33; 34] \\ R1234 yf & 267 & 241.92–324.00 & 0.44–21.64 & 0.05607–0.09158 & [35; 36] \\ R1234 ze(E) & 494 & 203.18–343.31 & 0.31–23.32 & 0.05893–0.11727 & [35; 36; 37] \\ R1234 ze(Z) & 61 \({}^{\text{a}}\) & 283.54–374.24 & 0.10–4.01 & 0.06520–0.09457 & [38] \\ R1336 mzz(E) & 118 & 253.68–353.51 & 0.03–4.06 & 0.05610–0.08160 & [39; 40] \\ R1336 mzz(Z) & 1279 & 191.58–399.42 & 0.05–68.52 & 0.05294–0.11810 & [41; 42] \\ \hline \hline \end{tabular}  
* In 2019, 40 experimental data were provided by Prof. [PERSON] through private communication.  
\end{table}
Table 1: Summary of the experimental liquid thermal conductivity data for low-GWP refrigerants studied in this work.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Refrigerant** & \(M\) & \(T_{b}\) & \(T_{c}\) & \(p_{c}\) & \(\omega\) & **Source** \\  & **kg kmol\({}^{-1}\)** & **K** & **K** & **MPa** & **\(\omega\)** & **Source** \\ \hline R1224 yd(Z) & 148.487 & 287.77 & 428.69 \({}^{\text{a}}\) & 3.33 \({}^{\text{a}}\) & 0.3220 & [43] \\ R1233 zd(E) & 130.496 & 291.41 & 439.60 & 3.62 & 0.3025 & [44] \\ R1234 yf & 114.042 & 243.67 & 367.85 & 3.38 & 0.2760 & [44] \\ R1234 ze(E) & 114.042 & 254.18 & 382.51 & 3.63 & 0.3130 & [45] \\ \hline \hline \end{tabular}  
\end{table}
Table 2: Physical properties for the studied alternative refrigerants.  
Figure 1: Liquid thermal conductivity behavior of the analyzed halogenated alkene refrigerants as a function of the reduced temperature (**a**) and the reduced pressure (**b**).