## 1 Introduction  
The regulations and legislative acts adopted by the European Union led to the successive phase-out of chlorofluorocarbons (CFCs) and hydrochlorofluorocarbons (HCFCs) and the phase-down of hydrofluorocarbons (HFCs). The F-Gas regulation (EU Regulation No517/2014) aimed to reduce greenhouse gas emissions by 2030, and its focus is on a drastic phase-down of HFCs. Refrigeration technology development made it possible to use some groups of refrigerants, such as hydrofluoroolefins (HFOs) and hydrochlorofluoroolefins (HCFOs), with a much lower global warming potential (GWP) than that of HFCs. In addition to these refrigerants, hydrocarbons have attracted attention as interesting alternatives to HFCs because of their low GWP values [1, 2]. In the early twentieth century, hydrocarbons were used as refrigerants in refrigeration systems. Still, nonflammable CFCs replaced them because of the technical and safety concerns related to the use of hydrocarbons at that time. The main drawback of hydrocarbons that limits the use of these refrigerants is their flammability characteristic. To mitigate this problem, a minimal refrigerant charge in a refrigeration system is recommended by experts. Simultaneously, there are safety regulations and precautions that must be met when installing large-volume refrigeration equipment. Containing the hydrocarbon in a sealed system, minimizing the charge of hydrocarbons for a specific application, minimizing the concentration of hydrocarbons in the ambient air (lower than the flammability limit) using a proper ventilation source, and eliminating the source of ignition are some of the main precautionary instructions that must be taken into consideration when using hydrocarbons [3; 4; 5]. In addition to the very low GWP and zero ozone depletion potential (ODP) values, hydrocarbons have other advantages, such as their low cost, compatibility with mineral and alkyl-benzene oils, and availability [6], as well as excellent thermodynamic and suitable physical and chemical properties. Together, these advantages make hydrocarbons long-term alternatives to heat pumps and refrigeration systems [7]. Many experimental, analytical, and numerical studies have focused on the performance of heat pumps and refrigeration systems when using hydrocarbons as refrigerants [8; 9; 10; 11; 12]. These studies examine the use of hydrocarbons in their pure forms or mixed with HFCs or HFOs. The energy performance of a commercial refrigeration system using R290 instead of R22 was studied experimentally by [PERSON] et al. [13]. According to their results, the cooling capacity of the R290 refrigeration unit decreased by 13-20%, while the COP of the unit increased by 1% to 3% compared with R22. In another study, the performance of a residential air conditioning system was explored by [PERSON] and [PERSON] [14]. They investigated the effect of different refrigerants, including R22, R290, R407C, and R410A, on the system's performance when operating at high condensing temperatures. Their results showed that the highest cooling capacity and power consumption of the system were observed with R410A. By contrast, the lowest power consumption and refrigerant charge were observed when the system operated with R290. The performance of a reversible water-to-water heat pump when operating with R407C with R290 was investigated by [PERSON] et al. [15]. Their results indicated that the system's capacity when using R290 was lower, in the range of 9-13%, compared with the capacity using R407C in the heating mode. By contrast, the COP of the system was higher when using R290. According to the results, a 9% to 15% increase in the heating COP was achieved using R290 instead of R407C. The energy performance of an automotive air conditioning system using hydrocarbon mixtures composed of R290/R600/R600a was studied experimentally by [PERSON] et al. [16], and the results were compared to a case that used R134a. According to their findings, every hydrocarbon mixture ratio resulted in a higher system COP than R134a. [PERSON] et al.