Experimental evaluation of low-GWP refrigerants as drop-in alternatives to R23 for ultra-low temperature refrigeration

• R469A and R472B are evaluated as drop-in alternatives to R23 for ULT applications. • Pull-down and hysteresis operation of a commercial ULT freezer is investigated experimentally. • Different freezer temperatures have been evaluated: –70, –60, and –50 °C. • R469A and R472B performance is better with higher freezer temperatures, reducing energy consumption by up to 17% at –50 °C compared to R23. • Switching from R23 to R469A or R472B reduces CO 2 equivalent emissions by up to 50%. The transition towards low-GWP refrigerants in ultra-low temperature (ULT) refrigeration is hindered by the absence of regulatory frameworks. Thus, traditionally employed refrigerants, such as R23 or R508A, continue to dominate current usage despite their high GWP. This paper presents the first comprehensive experimental evaluation of two recently developed lower-GWP refrigerants, R469A (GWP = 1357) and R472B (GWP = 526), as drop-in alternatives to R23 (GWP = 14600) in an R404A/R23 commercial two-stage cascade ULT freezer. To simulate realistic and representative operating conditions of a typical ULT freezer, the investigation initially focused on the pull-down performance from ambient temperatures of 15, 20, and 25 °C to a target temperature of − 70 °C. Subsequently, hysteresis operation with those ambient temperatures and set freezer temperatures of − 70, −60 and − 50 °C was examined. Results demonstrated that both R469A and R472B incurred longer pull-down durations (up to 60 and 47 min slower, respectively), along with increased energy consumption (up to 23% and 34% higher, respectively) compared to R23. As for the hysteresis operation, R469A and R472B performed better with higher freezer temperatures, reducing energy consumption by 10–17% at − 50 °C and increasing it by 14–16% at − 70 °C relative to R23. Regarding the environmental performance, the significantly lower GWP values of R469A and R472B translated into substantial reductions in overall CO 2 equivalent emissions, achieving up to a 50% decrease in environmental impact when compared to R23.