Optimal design and environmental, energy and exergy analysis of a vapor compression refrigeration system using R290, R1234yf, and R744 as alternatives to replace R134a

Abstract

Abstract This paper presents a steady-state model of a vapor compression refrigeration system (VCRS) that produces 1200 l of chilled water (5 °C) for an indirect expansion air-conditioning system (IEACS) and 600 l of hot water (40 °C) for bath. The proposed model was used to design a VCRS with reduced geometric structure and to compare the environmental, energy and exergy performance of R290, R1234yf, R744 with R134a. Also, this model uses for each refrigerant volumetric and global efficiency curve obtained from commercial compressors. The metrics applied to assess the environmental, energy and exergy performance are respectively the TEWI (Total Equivalent Warming Impact), COP and Exergy Efficiency. Besides, an optimization method was applied to a range of values related to the diameters of the water and refrigerant tube to reduce the geometric structure of the VCRS to an optimal size. COP analysis indicated that the optimized system operating with R290 presented higher energy performance for an evaporation temperature of −3 °C and condensation/gas cooling temperature of 45 °C. TEWI analysis showed that the system with R290 has higher environmental performance for an evaporation temperature of −3 °C and condensation/gas cooling temperature of 45 °C. For this thermodynamic condition, the system with R290 also presented higher exergy efficiency. Finally, a comparative study was performed to evaluate the refrigerant charge in the optimized systems. The results show that the refrigerant charge in the systems with R744, R1234yf and R134a is 102.4%, 126.9%, 114.2% respectively higher than the refrigerant charge in the system with R290 for the established thermodynamic condition.