## 1 Introduction  
Today, it is confirmed that the human-made emissions of greenhouse gases (GHGs) are responsible for climate change [1]. One of the sectors with a noticeable contribution to GHGs emissions is the refrigeration, air conditioning and heat pump (RACHP) sector. It is estimated that the RACHP sector was responsible for 349 MCO\({}_{2}\)-eq. in 2010 and is predicted to pass 1596 MtCO\({}_{2}\)-eq. in 2030 [2]. According to the International Institute of Refrigeration (IIR), 37% of GHG emissions were related to indirect emissions caused by electricity consumption of the refrigeration systems and 37% was related to direct emissions due to the escapes of refrigerants [3, 4]. After global efforts to phase out the chlorinated fluids to protect the ozone layer, as a result of the Montreal protocol [5], it was time to focus on phasing down/out of GHGs to reduce the emissions of these gases. These efforts were started in 1997 by signing the Kyoto protocol. Later, it was reinforced through the F-Gas Regulation in the European Union in 2014 and the Kigali amendment to reduce the use of hydrofluorocarbon (HFC) refrigerants by 80% until 2047 [6, 7, 8]. Although the Montreal protocol covered the chlorinated products, it is worth mentioning that the phase-out of chlorofluorocarbon (CFC) refrigerants, as the chlorinated products, reduced global warming by 25% [9]. This is due to the very high global warming potential (GWP) values of CFCs. To reduce the GHG emissions of the RACHP sector, alternative refrigerants with lower GWP values have been developed to substitute currently used HFCs with higher GWP. The global warming impact of the RACHP system is associated with direct and indirect emissions. Therefore, the GWP values of the alternative refrigerants and the energy efficiency of the system operating with these refrigerants must be taken into account [10,11]. Different metrics have been proposed to quantify the equivalent environmental impact of the RACHP systems [12]. The Total Equivalent Warming Impact (TEWI) is one of the metrics widely used to quantify the direct and indirect equivalent CO\({}_{2}\) (CO\({}_{2}\)-eq.) emissions of the RACHP systems [13]. In many studies, TEWI is used to investigate the warming impact of RACHP systems and the benefit of alternative refrigerants to reduce the CO\({}_{2}\)-eq. emissions [14, 15, 16, 17, 18, 19, 20, 21]. [PERSON] et al. [14, 15] investigated the influence of using R134a, R436A and R600a in a domestic refrigerator. Their results revealed that R436A and R600a reduced the TEWI by 16 and 21% compared to R134a. The TEWI analysis was performed by [PERSON] et al. [16] to study the warming impact of a domestic refrigerator with automatic defrost when using R134a and R1234 yf. They reported that by using the Mexican Norm NOM-015-ENER-2012, and the CO\({}_{2}\)-eq. emissions of the electricity production in Mexico, the use of R1234 yf increased the TEWI of the system. [PERSON] et al. [17] investigated the TEWI of a supermarket refrigeration system designed for R404A and retrofitted by R449A. Considering two different refrigerant leakage rates, they reported that R449A, instead of R404A, reduced the TEWI of the refrigeration system by 50 and 16% at the leakage rates of 12 and 0.4%, respectively. A comparison between an R744 transcritical cycle and a commercial refrigerator operating with R134a was made by [PERSON] et al. [18]. They studied the influences of the refrigerant charge amount and the utilization of an internal heat exchanger (IHX) to reduce the TEWI of the refrigeration systems. Their study revealed that IHX reduced the TEWI by about 3% due to the improvement of the system's energy efficiency. They also reported the optimum refrigerant charge amount that minimizes the TEWI of the system. The objectives of the regulations related to the GHGs emissions indicate that the main focus of these regulations is on limiting the direct emissions of the RACHP systems by a stepwise phase-down/out of GHGs with relatively high GWP values.