This paper presents the experimental comparative performance analysis of an automotive air conditioning (AAC) system using R1234yf and R134a. For this purpose, an AAC experiment setup used for R134a was built to obtain the drop-in performance of a new refrigerant R1234yf. Among the low global warming potential (GWP) refrigerants, R1234yf was particularly chosen due to its similar thermo-physical properties with R134a. However, the system with R1234yf could not perform as efficiently as R134a can. Therefore, an internal heat exchanger (IHX) was employed to enhance the performance of the R1234yf system. After that, the performances of R1234yf and R134a were compared under various compressor speeds and air stream temperatures. The results showed that the cooling capacity and COP of the system with R1234yf were 17.1 % and 12.4 %, respectively, lower compared to the one with R134a. However, when the IHX was introduced into the system with R1234yf, the cooling capacity and COP values were significantly enhanced by 7.9 % and 4.1 %, respectively.

A ccording to European Commission (EC) Regulation No 517/2014, Directive No 40/2006 was rearranged so that usage of refrigerants that have GWP value higher than 150 is prohibited in mobile air conditioning systems by 2022 [1, 2]. Thus, finding a new alternative refrigerant to R134a (GWP=1430) has become a necessity and recent studies mainly have been focusing on this topic [3]. Refrigerants such as R152a, R1234yf, R1234ze and R744 (CO2) were suggested in the literature as environment friendly refrigerants [4, 5, 6, 7]. As an alternative refrigerant, R1234yf (GWP=4) has attracted great attention due to its similar thermophysical properties in comparison with R134a [7, 8]. Therefore, various theoretical and experimental comparison studies about R1234yf can be found in the literature. Among them; Naushad et al. theoretically investigated R1234ze and R1234yf as alternatives to R134a in simple vapour compression refrigeration system. They claimed that R1234yf can be a good alternative to R134a after made some necessary modifications, such as selecting suitable compressor oil and pipe sizes. On the other hand, their study showed that R1234ze requires bigger