Optimization of the composition of mixtures based on R744 and hydrocarbons: Efficiency and Prospects

DOI: 10.18462/iir.compr.2024.0630

Sekcia: Compressors and refrigerants

Stav prijatia: Abstrakt prijatý

Autori

Abstrakt

This paper focuses on the theoretical analysis and search for optimal ratios of binary mixtures of CO2 with propane, butane, isobutane and ethane in a simple reverse cycle to achieve energy efficiency goals. The optimum ratio is determined to within 0.5% molar fraction based on maximizing the coefficient of performance (COP). The study also evaluated the volumetric cooling capacity (qν) of the resulting blends. The calculations were performed at a heat rejection temperature of +30°C and a boiling point of -30°C. In this paper, both subcritical and transcritical operation modes are considered. In the case of transcritical operation, the optimal heat removal pressure is additionally determined with an accuracy of 500 Pa, which maximizes the COP. The boiling and condensation temperatures are determined as the average values between the phase transition temperatures at a given pressure (glide temperatures). The results of the study allowed us to determine the optimal molar fraction ratios for R744/R600 and R744/R600a blends, which were 49/51% and 47.5/52.5%, respectively. The resulting COP value was 10.1% and 5.1% higher than that of pure R600 and R600a. In addition, their volumetric cooling capacity increased by 7.8 and 5.3 times, respectively. The study of R744/R290 and R744/R170 blends revealed their lower efficiency from the energy point of view. Based on the results obtained, it was concluded that R744/R600 and R744/R600a blends can be used as an alternative to pure R600 and R600a, but the need for further, more in-depth research on this issue is indicated.

Kľúčové slová

Binary mixtures
R744
R290
R600
R600a
R170
Energy efficiency
COP
Volumetric cooling capacity