Abstract
In this study, the energetic and exergetic performance merits of an automotive air condition-ing (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 refrig-erant 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.
Highlights
Cars equipped with air conditioning systems first appeared in the 1930s after the development of Chlorofluorocarbon group refrigerants
CO2 has extremely high compressor discharge pressures leading to heavy equipment and yields a relatively low coefficient of performance (COP).With a global warming potential (GWP) of only 4 and higher energy effectiveness compared to R1234ze, R1234yf is presently considered as the best substitute for R134a, it has mild flammability as listed in A2L classification [2, 3]
The values of the system performance parameters were determined with respect to the compressor speed and air stream temperatures incoming the condenser and evaporator
Summary
Cars equipped with air conditioning systems first appeared in the 1930s after the development of Chlorofluorocarbon group refrigerants. Navarro et al [6] performed comparative tests of a bus air conditioning system using R1234yf, R134a, and R290, and determined that R1234yf yielded a lower COP and about 10°C lower compressor discharge temperatures than the other two refrigerants. Cho and Park [13] determined that an AAC system with R1234yf yielded 4.0−7.0% lower cooling capacity, 3.6−4.5% less COP, and 3.4−4.6 lower second law efficiency relative to the system with R134a In their theoretical analysis of an AAC system for R134a and R1234yf, Golzari et al [14] found that R1234yf had a higher exergetic efficiency, and the compressor was the component causing maximum exergy destruction. It consists of the AAC system components employed in a compact automobile, namely a fixed-capacity wobble-plate compressor, parallel-flow micro-channel condenser, laminated evaporator, TXV, liquid receiver, and filter/drier. Measurements of physical variables such as pressure, temperature, relative humidity, airspeed, compressor
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