System modifications with a nonflammable eco-friendly mixture for ultra-low-temperature refrigeration: Energy, advanced exergy, life cycle analysis

Being widely used in various fields, ultra-low-temperature (ULT) refrigeration plays an important role in society development. Refrigeration systems using zeotropic mixtures are favored in existing studies, but efficient options suffer drawbacks of flammability risk, limiting broader applications. In this work, a novel ternary mixture of R1132a, CO₂ and R1336mzz(E) is proposed, with the flammability predicted and conditionally avoided. Configuration modifications are customized for this mixture for efficiency enhancement at refrigerating temperature down to −80 °C. This novel system exhibits maximum COP improvements of 17.7 % and 6.0 %, versus a basic auto-cascade system and a complex cascade system respectively. Thus, an annual performance factor improvement of up to 5.4 % is achieved globally, mainly attributed to low throttling and recuperative irreversibilities. Advanced exergy analysis indicates that this novel system has the highest improvement potential, with an avoidable loss ratio of 66.9 %. Meanwhile, this novel system can reduce life cycle cost worldwide, with a maximum of 5.51 % in Singapore. A superiority in life cycle climate performance is also achieved, with emission reductions of up to 10.6 %. The results indicate simple-structured, safe, efficient, high-potential, cost-effective and low-carbon-emission solutions for ULT technology, contributing to energy conservation and emission reduction worldwide, and finally promoting carbon neutrality.