Comparison of the Thermodynamic Performance and Total Equivalent Warming Impacts of Various Refrigerants Alternative to R134a in Automobile Air Conditioning Systems for Cooling Mode Operations

Overview

This study evaluates the thermodynamic performance and warming impact characteristics of five refrigerant alternatives to R134a in automobile air conditioning systems operating in cooling mode. The comparative analysis encompasses energetic and exergetic parameters for R1234yf, R1234ze(e), R152a, R430A, and R440A across standardized evaporating and condensing temperatures with a fixed cooling capacity of 4 kW. Direct and indirect total equivalent warming impacts were calculated for vehicles fueled with gasoline, diesel, and liquefied petroleum gas.

Methods and approach

Thermodynamic performance was assessed through coefficient of performance and exergetic efficiency calculations for each refrigerant under specified operating conditions. Energy and exergy destruction rates were quantified for individual system components, including compressor and evaporator. Total equivalent warming impact calculations incorporated both refrigerant-related emissions and fuel consumption effects for three fuel types. Comparative rankings were established across all evaluated refrigerants and vehicle fuel categories.

Key Findings

R440A demonstrated the highest energy and exergy efficiency, achieving 4.46% higher COP than R134a, while R1234yf and R1234ze(e) showed lower performance with COP reductions of 4.11% and 0.16% respectively. Exergetic analysis identified the compressor as the primary exergy destruction component across all refrigerants. For gasoline-fueled vehicles, R1234ze(e) exhibited the lowest total equivalent warming impact at 2857 kg CO2-equivalent compared to R134a's 5834 kg CO2-equivalent, representing a 51% reduction. The ranking from highest to lowest TEWI for gasoline vehicles was R134a, R440A, R152a, R430A, R1234yf, and R1234ze(e). Diesel-fueled vehicles demonstrated comparable TEWI values to gasoline cases, while LPG-fueled vehicles achieved 9-18% lower TEWI across all refrigerants. The air conditioning system contributed 9.5-10.5% of total vehicle TEWI regardless of fuel type or refrigerant selection.

Implications

The analysis demonstrates that thermodynamic efficiency and global warming potential reduction do not necessarily align in refrigerant selection for automotive air conditioning systems. R1234ze(e) achieves superior warming impact reduction despite marginally lower energy efficiency than R134a, indicating that direct emissions from leaked refrigerant significantly outweigh operational efficiency penalties in the overall climate impact assessment. R440A's superior thermodynamic characteristics position it as a technically optimal alternative, though its TEWI performance ranks third, suggesting that multi-criteria evaluation frameworks are essential for comprehensive refrigerant assessment.

Scope and limitations

This summary is based on the study abstract and available metadata. It does not include a full analysis of the complete paper, supplementary materials, or underlying datasets unless explicitly stated. Findings should be interpreted in the context of the original publication.