); gianluc.morini3@unibo. In order to further increase the seasonal coefficient of performance (COP) of heat pump systems and decrease their environmental impact, over the last years, particular effort has been paid to the use of alternative refrigerant fluids [7; 8]. In particular, [PERSON] et al. [7] carried out an experimental analysis on different refrigerants (R513A, R516A, R1234 yf and R134a) used in vapor compression cooling and heating systems considering the same steady-state conditions. The authors reported that in cooling mode R513A presented the highest system COP (up to +8%), while R516A showed the lowest system COP at the highest evaporation temperature; however, it exhibited the highest COP and capacity at the lowest evaporation temperature. [PERSON] et al. [8] conducted a comparative analysis on a gas-engine heat pump operating with R152a and R134a, without any changes in lubricant or components; the results showed that using R152a the primary energy ratio increased by 2.6-10.4% and the natural gas consumption rate dropped by 6.0-9.5% with respect to R134a. Coherently with this research, in the last decades, a series of protocols and regulations have been promulgated to force manufacturers of air-conditioning and refrigeration units to change the adopted refrigerants. As an example, with the Montreal Protocol [9], emanated in 1987, a plan was implemented to progressively phase out the synthetic refrigerants involved in ozone depletion, such as chlorofluorocarbon (CFC) and hydrochlorofluorocarbon (HCFC). Due to the ban of the abovementioned fluids, hydrofluorocarbon (HFC) refrigerants, characterized by a null impact on the ozone layer (ozone depletion potential (ODP) equal to zero), were developed and commercialized [10; 11; 12]. Unfortunately, HFCs have a strong environmental impact since their emission in the atmosphere contributes to an increase in global warming. Since the adoption of the Kyoto Protocol [13], by means of which the joining countries committed a series of interventions to reduce global GHG emissions, the European HVAC market has been continuously influenced by several regulations and protocols aimed at decreasing the environmental impact of air-conditioning and refrigerating units. Currently, the UE protocol 517/2014 [14], known as the \"F-gas Regulation\", imposes to reduce by 2030 whole HFC emissions by at least two-thirds with respect to 2014 levels. In order to obtain these outcomes before the prescribed deadline, the regulation has introduced an incremental phasedown of HFC refrigerant fluids, forcing an increasing reduction in the quantity of these fluids that can be commercialized on the market. In addition, strict limits on the mean GWP value of the refrigerants available on the market in the next years have been introduced. As an example, for the 2021-2023 period, the mean GWP value of the refrigerating fluids sold in Europe must be equal to 1035. Additional measures to limit the GHG market have been imposed by the Kigali Amendment (2016) to the Montreal Protocol [15], which outlines a steady 80-85% phaseout of HFCs by the late 2040s. For all the abovementioned reasons, recently, researchers from both industrial and academic fields have been studying with great interest the development and the use of alternative refrigerants, characterized by lower environmental effects and able to guarantee proper energy performance in HVAC units, such as hydrofluoroolefins (HFOs). Aspects such as environmental impact, safety issues, the replacement of these refrigerants within existent systems and overall energy efficiency have been studied by the scientific community [16]. Currently, refrigerant R-410A is the most widespread fluid within conditioning systems for residential applications, and for this reason, several studies on alternative refrigerants with lower GWP have been conducted over the last years. Among the others, it is worth mentioning the experimental results reported in [17; 18; 19].