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.

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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

This study represents an experimental and numerical investigation of the enhanced prototypes of the induction air heaters. For this purpose, flow field is enhanced in order to avoid turbulence. The air mass flow rate, outlet construction and the application of insulation of the outer surface of the heater were selected as the performance enhancing parameters. Depending on the exit construction, the new designed prototypes are named as K-2 and K-3. Experiments were performed under two groups for three various flow rates. In the first group, non-insulation situation is examined. In the second group tests, insulation is applied to the outside of windings and inlet-outlet flaps which constitute the boundary of the control volume for the prevention of heat losses. The increasing flow rate boosted the thermal efficiency by 9%. Each of insulation and enlarging exit cross section increased the thermal efficiency by 13%. It was observed that the thermal power transferred to air with the new prototypes increased about 246 W more than the previous designs. The thermal efficiencies of the K-2 and K-3 type heaters were calculated as 77.14% and 87.1%, respectively.

This study presents the energy and exergy analysis of a R1234yf automotive air conditioning system. For this aim, an experimental baseline automotive air conditioning system was developed and a double pipe internal heat exchanger was employed to the system. The detailed performance comparison of the system under different condensation and evaporation temperatures was studied for both the baseline system and the system with the internal heat exchanger. For this, the cooling capacity, COP, and the total exergy destruction per cooling capacity were evaluated. Additionally, the volumetric and isentropic efficiencies of the compressor were investigated. It was determined that the internal heat exchanger has increased COP and decreased exergy destruction per cooling capacity by 4%-6% and 13%-16%, respectively.