Abstract
This paper investigates the results of a Second Law analysis applied to a mobile air conditioning system (MACs) integrated with an internal heat exchanger (IHX) by considering R152a, R1234yf and R1234ze as low global warming potential (GWP) refrigerants and establishing R134a as baseline. System simulation is performed considering the maximum value of entropy generated in the IHX. The maximum entropy production occurs at an effectiveness of 66% for both R152a and R134a, whereas for the cases of R1234yf and R1234ze occurs at 55%. Sub-cooling and superheating effects are evaluated for each one of the cases. It is also found that the sub-cooling effect shows the greatest impact on the cycle efficiency. The results also show the influence of isentropic efficiency on relative exergy destruction, resulting that the most affected components are the compressor and the condenser for all of the refrigerants studied herein. It is also found that the most efficient operation of the system resulted to be when using the R1234ze refrigerant.
Highlights
During the last two decades, R134a has been one of the most important refrigerants used in domestic refrigeration, air conditioning systems, and chillers
The maximum entropy production occurs at an effectiveness generation values is found to be the R152a, this is because its specific heat capacity is higher than that of
The results show that greatest exergy efficiency is R152a, overcoming R1234yf by 16%, while the therefrigerant difference with the greatest exergy efficiency is
Summary
During the last two decades, R134a has been one of the most important refrigerants used in domestic refrigeration, air conditioning systems, and chillers. Lee and Jung [8] evaluated the energetic performance in an experimental test bench working with R1234yf under winter and summer conditions They concluded that it is a suitable refrigerant in mobile air conditioning systems, replacing R134a. Cho and Park [16] conducted an exergy analysis of a MAC including an IHX and evaluating the system at different compressor speeds, both refrigerants R1234yf and R134a were compared, and very similar behaviors were found. Pottker and Hrnjak [17] studied the effect of sub-cooling on the COP of a MAC system using both R134a and R1234yf as refrigerants; experimental results showed good performance for the system operating with R1234yf when an IHX was used with a relatively high degree of sub-cooling.
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