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An automotive air conditioning and heat pump (AAC/AHP) system employing refrigerants R134a and R1234yf was developed and tested in cooling and heating operation modes under broad ranges of compressor speed and air inlet temperature conditions. Using test results, various energetic and exergetic performance parameters of the system were evaluated and compared. The R1234yf system provided on average 5.8% lower cooling capacity, 0.2% higher heating capacity, 11.9% lower COP for cooling and 3.6% lower COP for heating relative to the R134a one. Furthermore, the exergetic efficiency of the R1234yf system were on average 17.6% and 14.7% lower compared to the R134a one in cooling and heating modes, respectively. The major contributor to the exergy destruction in the system is the compressor for both refrigerants and operation modes. These results reveal that R1234yf performs better in heating relative to cooling mode, and it can be used as a replacement for R134a in not only AAC but also AHP systems in expense of slightly lower energy effectiveness. [ABSTRACT FROM AUTHOR]