Energetic and exergetic performance comparison of an experimental automotive air conditioning system using refrigerants R1234yf and R134a.

In this study, the energetic and exergetic performance merits of an automotive air conditioning (AAC) system using R134a and R1234yf have been investigated. For this aim, a laboratory AAC system was developed and equipped with devices for mechanical measurements. The refrigeration circuit of the system mainly had an evaporator, condenser, liquid receiver, fixed capacity compressor, and thermostatic expansion valve. The tests were performed by changing the compressor speed and air stream temperatures incoming the condenser and evaporator. Based on energy and exergy analysis, various performance parameters of the AAC system for both refrigerants were determined and presented in comparative graphics. It was found that R1234yf resulted in 0.4-10.9% lower refrigeration capacity, 5.5-11.6% lower COP, and 4.7-16.1°C lower compressor discharge temperature, while yielding 9.3-22.3% higher refrigerant mass flow rate and 1.1-3.5°C higher conditioned airstream temperature in comparison to R134a. Moreover, the components of the R1234yf system usually destructed more exergy, and the total exergy destruction rate per unit refrigeration capacity of the R1234yf system was 4.1-15.3% greater than that of the R134a one. [ABSTRACT FROM AUTHOR]