Experimental energy and exergy performance of an automotive heat pump using R1234yf

Abstract

Various energy and exergy performance parameters of an automotive heat pump (AHP) with R1234yf have been investigated and compared with those of the baseline system with R134a. For this aim, an AHP system was set up from the components of an air-conditioning system employed in a compact car and equipped with instruments for mechanical measurements. It was tested with R1234yf and R134a by changing the compressor speed and air stream temperatures incoming the outdoor and indoor units. Using test data, energy and exergy analyses of the AHP were performed, and its performance parameters were evaluated. The R1234yf system provided conditioned air temperatures in the range of 29.9-59.3 degrees C, heating capacities in the range of 1.96-3.14 kW and coefficient of performance (COP) values in the range of 2.44-4.56. It yielded 3.3-10.8 degrees C lower conditioned air temperature, 9.2-15.4% lower heating capacity, 1.6-7.1% lower COP, 13.8-21.6 degrees C lower compressor discharge temperature, 3.1-19.2% higher total exergy destruction rate per unit heating capacity but significantly less TEWI in comparison with the system with R134a. Moreover, the R1234yf system yielded larger exergy destructions in the outdoor unit, compressor and expansion device but lower exergy destruction in the indoor unit. These findings reveal that R1234yf can be used in AHP systems in expense of less heating capacity, lower COP and higher exergy destruction rate per unit heating capacity in comparison with R134a.