The refrigeration systems in high-and low-temperature test chambers face challenges of high energy consumption and low efficiency. This study developed an enhanced vapor injection system in a test chamber and conducted experiments using R448A and R404A refrigerants to improve the system efficiency and ensure its alignment with low-carbon environmental goals. The impact of refrigerant charge amounts and compressor frequencies on system performance was analyzed. The results demonstrated that the cooling capacity and coefficient of performance(COP) of the R404A and R448A systems initially increased and then decreased with increasing refrigerant charge amounts. The R448A system demonstrated an 11.3% higher maximum cooling capacity and a 10.4% higher COP than the R404A system. In addition, the compressor power consumption of the R448A system was lower than that of the R404A system. At a refrigerant charge amount of 2.0 kg, the R448A system consumed 7.5% less power than the R404A system. The refrigeration capacity of the R448A system exhibited a 7.7% higher increase compared with that of the R404A system, whereas the compressor power consumption increase was 1.9% lower than that of the R404A system.

R404A is a widely used medium-temperature refrigerant in low-and medium-temperature refrigeration systems because of its excellent efficiency and ozone-friendly properties. However, its high Global Warming Potential (GWP=3922) has led to its scheduled phase-out by 2030. R448A has emerged as a key alternative, offering superior thermophysical properties and a significantly lower GWP. This study investigated a refrigeration system in high-and low-temperature test chambers to explore the operating conditions for the case of R404A replaced by R448A. The results showed that the cooling capacity and coefficient of performance (COP) of both systems initially increased and then decreased with increasing refrigerant charge. The optimal charge for R448A was approximately 9.3% higher than that for R404A, and its cooling capacity and COP improved by over 17%. At the same evaporation temperature, the R448A system was less sensitive to ambient temperature fluctuations. A 10 ℃ increase in ambient temperature resulted in a 16.9% decrease in cooling capacity for R404A, whereas R448A only experienced an 8.6% decrease. Additionally, the maximum COP of the R448A system was approximately 9.9% higher than that of R404A. The return on investment for R448A is approximately one year, and as the system's life cycle progresses, the total annualized cost (TAC) of R448A becomes lower than that of R404A, with annual savings ranging from 0.6% to 6.6%. Replacing R404A with R448A can reduce total carbon emissions by over 32%, with approximately 27% of this reduction attributed to refrigerant leakage during operation and end-of-life recycling.