## 7 Analysis of Working Fluids for Low-Temperature ORC
The screening method is a popular approach for fluid selection but has limitations as it does not fully consider the practical design of the cycle. An alternative is the operating map approach, a pre-selection tool that considers the interaction between the expander, heat exchangers, and the working fluid to narrow down the possible choices. The study reported below complements the data presented in Table 3 with a summary derived from recent literature, offering insights into the performance of ORC systems when integrated with low-grade WHR. The study by [92] addresses the selection of working fluids for an ORC driven by refinery waste heat. The authors analyzed the performance of several substances of the R-type family. Fixing the condensation temperature at 45 \({}^{\circ}\)C, the R-fluids offered thermal efficiencies ranging between 7% and 17% at evaporation temperatures of 100-195 \({}^{\circ}\)C. The focus primarily rests on four candidates: R600a, R236 ea, R227 ea, and R601. When the target temperature of the waste heat source was higher than 120 \({}^{\circ}\)C, R601 appeared as the optimum working fluid. The findings indicated that R600a showed the highest thermal efficiency and maximum power output, and it recovered the entire waste heat under all evaporation temperatures. R236 ea exhibited almost the same thermal efficiency as R600a while maintaining robust performance. Conversely, R227 ea and R601 had higher thermal efficiency under a few conditions but generally performed less satisfactorily. [PERSON] et al. [93] analyze the behavior of ORC systems adopting several working fluids (e.g., benzene, acetone, propane, ethanol, and methanol, in addition to the conventional R-fluids, like R134a and R245 fa). The results highlight thermal efficiency increases associated with evaporator pressure changes (globally 10-18.5% at 11-15 bar, spanning an evaporator temperature of 70-227 \({}^{\circ}\)C) and decreases with condensation temperature increase. In this study, benzene is selected as the best fluid, implying significantly improved efficiencies for several operating conditions compared to other ORC fluids. In [90], the performance of various organic working fluids in a geothermal ORC system is studied. Five fluids are used while evaluating thermal efficiency, pump power consumption, and the exergy efficiency of the system. The study concludes that R113 exhibits the best overall performance, while R245 fa has a slight advantage over other fluids in terms of turbine power output. Considering the refrigerant, the study suggests that R600a has a superior ratio of area-system power, although the pump power required is significantly higher than other organic working fluids. A maximum system thermal efficiency of 5-5.5% is assessed at 100 \({}^{\circ}\)C, according to the fluids selected (R600a, R245 fa, R141, R123, R113b). The article in [86] discusses the experimental characterization of an ORC system for geothermal energy conversion. The system consists of a recuperative ORC equipped with a scroll expander and a direct contact evaporator (water/organic fluid) with counter-current gas/water heat exchange. The heat source temperature range was 65-85 \({}^{\circ}\)C, while the operating pressure was 10.9-16.8 bar. The experimental results showed that the tested system can operate with 5% efficiency using R123. The paper by [95] presents a simulation study on an ORC system with four different working fluids, namely R134a, R32, R407a, and R422c, to determine the thermal efficiency of the system in various temperature setups of the evaporator and condenser. The study assumes a mass flow rate of 0.15 kg/s. The results show that the optimum and realistic efficiency is achieved using R32 with a thermal efficiency of 7.0% at the evaporator exit temperature of 75 \({}^{\circ}\)C and condenser exit temperature of 45 \({}^{\circ}\)C. The higher efficiency obtained using R407a and R422c seems to be uncompromised. [PERSON] [91] aims to assess the thermodynamic performance of 20 working fluids for an ORC.