IJR highlights: review of low-GWP alternative refrigerants
In a recent review article based on over 60 published studies and published in the International Journal of Refrigeration, Chinese researchers have compared nearly 40 alternative low-GWP refrigerants in terms of performance, refrigerating capacity, safety and environmental impact.
The existing low GWP refrigerants have been divided into two categories: pure refrigerants and mixed refrigerants. Pure refrigerants can be divided into three types:
- HFCs with medium and low GWP, such as R32, R152a, R161, etc.;
- HFOs and HCFOs, such as R1234yf, R1234ze(E), R1234ze(Z), R1336mzz(Z), R1233zd(E), etc.;
- natural refrigerants, including carbon dioxide (R744), ammonia (R717), water (R718), hydrocarbons such as propane (R290). Mixed refrigerants are mainly mixtures of HFCs and HFOs.
In particular, the authors compared the coefficient of performance and refrigerating capacity of three high-GWP HFC-based refrigerants: R134a, R410A and R404A. They concluded that R513A (GWP of 573) has excellent overall performance as a substitute for R134a, while R466A (GWP of 733) is a good substitute for R410A. Both alternatives are classified A1 according to ASHRAE Standard 34, meaning no flame propagation and lower toxicity. Regarding R404A, they considered that R454A, R454C, R457A, R459B and R468A could be used as long-term substitutes in systems with a charge of less than 1.2 kg. Considering the refrigerating capacity, R454A is the preferred substitute for R404A . However, more work still needs to be done to find class A1 substitutes for R404A intended for high-charge refrigeration system.
The flammability of many refrigerants and its influencing factors such as air temperature and humidity have also been studied by the authors. In order to reduce flammability, some typical flame retardants can be added to form a non-combustible mixture in a certain proportion. However, hydrocarbons are more difficult to inhibit than halogenated hydrocarbons.
The authors conclude that since most of the existing alternative refrigerants with lower GWP are flammable, there is still no perfect compromise between safety and environmental protection. Therefore, while actively promoting the use of existing low-GWP substitutes to accelerate the phase-out of high-GWP refrigerants, it is necessary to strengthen the development of safe and environmentally friendly refrigerants.
Yang Z. et al. Analysis of lower GWP and flammable alternative refrigerants. This paper can be downloaded via the IIR’s FRIDOC database (free for IIR members)