## 4 Results and Discussion
### ORC Performances
#### 4.2.2 ORC Literature Comparison  
The present installation was analyzed in terms of global ORC performances regarding its thermal efficiency and its second law efficiency. To perform an accurate analysis in comparison with other ORC installations and working fluids, the best operating point of the ORC in pure NovecTM649 and the zeotropic mixture NovecTM649/HFE7000 were compared with those in the available experimental ORC literature database [23]. The global ORC performances have reached respectively for the pure fluid and the mixture the value of 5% and 5.6% for the net thermal efficiency, and the value of 20.8% and 22.4% for the net second law efficiency. These efficiencies refer to the experimental points with the highest power production at the expander outlet mentioned in the previous Section 4.1. To carry out the broadest comparison possible with the literature, efficiencies were screened as their gross efficiencies. The other calculated data for the optimized highest points are listed in Table 4. The T-s diagrams of the ORC for these two points are also presented in Figure 8. It can be noticed that, for the zeotropic mixture, the highest point corresponds to a good agreement between the evolution of the zeotropic glide and the evolution of the sink source temperature. Figure 7: The ORC performance according to electrical production in the pure fluid and the mixture (isoparameters). Extracted from the literature database, experimental ORCs were arranged from the lowest to the highest gross thermal efficiency or gross second law efficiency by their cumulative distribution function for the selected power range up to 10 kW and heat source temperature lower than 200 \({}^{\circ}\)C. This ordering method allows us to rank the ORC investigated in this study and to compare its performances to those of other installations. Figures 9 and 10 show the distribution of experimental ORCs. The present experimental test bench has a gross thermal efficiency of 6% for the NovecTM649 and 6.5% for the NovecTM649/HFE7000. These results allow us to rank the current ORC among the top 20% of the most efficient experimental installations (with an ORC distribution of around 0.8). This rating shows the potential of NovecTM649 and the zeotropic mixture NovecTM649/HFE7000 as pertinent fluid candidates to replace classical HFC or HCFC working fluids in comparison to the other new-generation fluids as observed in Figure 9. \begin{table}
\begin{tabular}{l c c c} \hline \hline
**Data** & & **NovecTM649** & **0.8 NovecTM649/0.2 HFE7000** \\ \hline \(\hat{m}_{hf}\) & (kg/s) & 0.4 & 0.4 \\ \(\hat{m}_{cf}\) & (kg/s) & 0.236 & 0.56 \\ \(\hat{m}_{uf}\) & (kg/s) & 0.065 & 0.057 \\ \(T_{in,hf,cup}\) & (\({}^{\circ}\)C) & 110 & 110.2 \\ \(T_{in,cf,omd}\) & (\({}^{\circ}\)C) & 13.5 & 12.6 \\ \(T_{ref}\) & (\({}^{\circ}\)C) & 13.5 & 12.6 \\ \(P_{in,inf,intur}\) & (bar) & 4.5 & 4.2 \\ \(P_{out,inf,tur}\) & (bar) & 0.53 & 0.45 \\ \(\hat{Q}_{heat}\) & (kW) & 12 & 10.8 \\ \(\hat{Q}_{cooling}\) & (kW) & 10 & 9.3 \\ \(\hat{W}_{el,tur}\) & (kW) & 0.715 & 0.703 \\ \(\hat{W}_{el,ps}\) & (kW) & 0.104 & 0.104 \\ \(\eta_{tur}\) & (\%) & 58.2 & 56 \\ \(\eta_{ls,tur}\) & (\%) & 61.4 & 61.5 \\ \(\eta_{th,net}\) & (\%) & 5 & 5.6 \\ \(\eta_{ll,net}\) & (\%) & 20.8 & 22.4 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: The calculated data for the optimized highest points. Figure 8: The T-s plot of the ORC cycle corresponding to the highest experimental point regarding electrical production: (**a**) NovecTM649; (**b**) 0.8 NovecTM649/0.2 HFE7000. To achieve a full comparison of the present installation and avoid any heat source temperature impacts on the ORCs performances ranking, a second law efficiency comparison was also done. With a gross second law efficiency of 24.3% for NovecTM649 and 26.3% for NovecTM649/HFE7000, the current ORC still ranked in the top 20% of the ORC installation performances as described in Figure 10, which confirms the previous discussion on the interest in these new-generation pure and mixed fluids.