Exergy and performance analysis of low GWP and Non-flammable HFO based refrigerant mixtures as alternatives to R134a

• Published in: Thermal science and engineering progress 2023-03, Vol.39, p.101691, Article 101691
• Main Authors: Kumma, Nagarjuna, Sarath, Sai, Harish Kruthiventi, S.S.
• Format: Article
• Language: English
• Subjects: Hydrofluoroolefins (HFOs); low GWP; Minimum inerting concentration; Ternary mixture
• ISSN: 2451-9049; 2451-9049
• DOI: 10.1016/j.tsep.2023.101691

•Modified thermal balance method (MTBM) is used to estimate the MICs (decides the flammability zone) of the mixtures considered in this study.•The inert effect of R227ea is superior when compared to the other dilutants considered in this study (R245fa, R134a and R125).•It is observed that the non-flammable zone condenses to a very small zone area in the flammability diagram once the GWP constraint is taken into account.•It is estimated that the exergy efficiency of the identified mixtures varied from 0.54 to 0.64. R1234yf and R1234ze(E) can be potential retrofits for the conventional refrigerants used in domestic refrigerator provided their flammability is controlled. In this study, the inerting effect of the dilutants R125, R134a, R227ea and R245fa on R1234yf and R1234ze(E) based ternary mixtures is studied theoretically. R152a, R161 and RE170 are used as the secondary refrigerants with R1234yf and R1234ze(E) based ternary mixtures. Minimum inerting concentration (most important parameter that decides the flammability of the mixture) is estimated with thermal balance method (TBM) and modified thermal balance method (MTBM) for the selected mixtures. The calculated MIC values are compared with 86 experimental data points (both binary and ternary) available in the literature. It is calculated that TBM and MTBM predicted the minimum inerting concentration values (for a majority of the mixtures) within ± 30 % and ± 8 % respectively when compared with the experimental data. The COP ratios of the non-flammable mixtures (that are proposed with MTBM) are estimated and is found to be maximum at a volumetric cooling capacity ratio close to 0.8. It is also calculated that the exergy efficiency varied between 0.54 and 0.64 for the low GWP mixtures (M1 to M5) proposed in this study.