## 1 Introduction
Several researchers have found it necessary and pertinent to outlinespecific qualifying criteria for a suitable WF in ORC systems. These are summarised for example, in [13; 14; 15]. Generally, pure fluids (composed of a single chemical constituent), were largely explored to be the operating medium of ORC machines. This study proposes binary mixtures as an alternative to single refrigerants such as WFs in ORC applications. Research has proved binary WF mixtures to be an effective method to enhance the performance of ORCs. Researchers have also suggested mixtures for different heat sources. Such WFs are able to match the temperature profile of the heat source by a non-isothermal phase change that decreases the irreversibility in the evaporator and the condenser. In other terms, a zeotropic mixture may better match the temperature profiles throughout evaporation and condensation based on temperature glides with changing constituent concentrations in every phase of the mixture. Mixtures of either hydrocarbons or siloxanes were explored by [PERSON] and [PERSON] [16]. For multicomponent mixtures, improved performance was seen, because the cooling device required less power. [PERSON] et al. [17] analysed a regenerative ORC system utilising four dry organic fluids to convert waste energy to power from low-grade heat sources. They confirmed that the composition of the WFs has significant impact on the ORC performance. [PERSON] and [PERSON] [18] compared three diverse compositions of R245 fa/R152a to pure R245 fa at a low temperature solar ORC. [PERSON] et al. [19] carried out experimental comparisons for a low-temperature solar regenerative ORC system. They used R245 fa as the pure fluid and compared the system performance to that with zeotropic mixtures of R245 fa/R152a (0.9/0.1) and R245 fa/R152a (0.7/0.3). They performed experiments at a heat source temperature of 110 \({}^{\circ}\)C with a constant volume flow rate. They found the average power output of R245 fa/R152a (0.7/0.3) was 28.03% higher than that of R245 fa/R152a (0.9/0.1) and 29.10% higher than that of R245 fa. The average overall efficiency of R245 fa, R245 fa/R152a (0.9/0.1), and R245 fa/R152a (0.7/0.3) was 0.88%, 0.92%, and 1.28%, respectively. The average estimated power output was between 6 and 8 W, and the average Rankine cycle efficiency was calculated to be between 4% and 6%, which both increases with the R152a content. [PERSON] et al. [20] investigated the performance of R227 ea, isobutane, R245 fa, isopentane, and their mixtures for geothermal heat source temperatures below 120 \({}^{\circ}\)C and arrived at the outcome that the second law efficiency of the mixtures increased in range between 4.3% and 15% compared to the best efficient pure component. [PERSON] et al. [21] found that a possible increase of 16% and 6% in cycle efficiency is obtained using mixtures for 150 \({}^{\circ}\)C and 250 \({}^{\circ}\)C heat sources. [PERSON] et al. [22] assessed isopentane, R245 fa, and their mixtures' performance in ORC for 106-151 \({}^{\circ}\)C heat sources and recommended isopentane/R245 fa (0.7/0.3). [PERSON] et al. [23] maximised the net power output on an ORC system by means of two cases with hot fluid inlet temperatures at 120 \({}^{\circ}\)C and 90 \({}^{\circ}\)C. They found that the optimised ethane/propane generated 12.9% higher net power output than the pure ethane with the hot fluid temperature of 120 \({}^{\circ}\)C. [PERSON] et al. [24] assessed the effect of the temperature glide during the zeotropic condensing process on the thermal efficiency and output work of the ORC system. [PERSON] et al. [25] examined the performance of eight pure WFs and their mixtures for a 150 \({}^{\circ}\)C heat source and the outcomes indicated that an increase in the second law efficiency in range of 7.1% to 14.2% was derived by the mixtures compared to pure WFs. [PERSON] et al. [26] found that R245 fa/R600a (0.9/0.1) was the best mixture among 10 groups of mixtures for a 120 \({}^{\circ}\)C geothermal heat source. [PERSON] et al.