Frigorigènes R32 et R290 : substituts aux R410A/R22 pour le conditionnement d'air utilisé dans les environnements à température ambiante élevée

Un rapport du Laboratoire National Oak Ridge compare la performance du R32 et du R290 en tant que frigorigènes à faible GWP alternatifs au R410A dans les conditionneurs d'air "mini-split" sous conditions de températures ambiantes élevées.
The final US Oak Ridge National Laboratory report – presented during MOP27 in Dubaï – compares the performance of low-GWP alternative refrigerants to HFC R410A in mini-split air conditioners (ACs) under high-ambient-temperature conditions. It looks at 4 R410A alternative refrigerants: the single component HFC refrigerant R32, Arkema’s ARM-71A, Chemours’ DR-55, Honeywell’s L-41 (R447A) and Mexichem’s HPR-2A, all A2L refrigerants with GWPs comprised between 461 and 677.

R32 was the only refrigerant that showed consistently better capacity and coefficient of performance (COP) than R410A at all test conditions (outdoor: 27.8°C, 35°C, 52°C (hot), 55°C (extreme). However, as previously observed, the potential negative aspect of R32 is its higher discharge temperature. ORNL tests have shown this to be 12-21°C higher than R410A, a characteristic which ORNL observes might negatively impact compressor reliability. DR-55 and HPR-2A had higher COPs than the baseline and matched the capacity of the baseline at both the hot and extreme test conditions. R447A and ARM-71A had lower cooling capacity than the baseline at all ambient conditions. R447A showed system COP improvements over R410A at high ambient temperatures, while ARM-71A, exhibited similar COP to R410A at all test conditions.

This final report also updates similar previous tests carried out on R22 alternatives by including results for propane (R290). R290, although classed as a flammable A3 refrigerant, exhibited consistently higher COP (+7 to + 11%) compared to R22 at all test conditions. However, it failed to match the cooling capacity of the baseline system (-5 to -11%).

All 4  other alternatives were found to deliver a lower performance than R22, both in terms of COP and cooling capacity. These were Chemour’s development blend DR-3, Honeywell’s N-20B and Solstice L20 (R444B) and Arkema’s ARM-20B, all A2L refrigerants with GWPs comprised between 295 and 904.

ORNL conducted tests using two “soft-optimized” ductless mini-split air conditioners provided by Carrier. Both units had a cooling capacity of 5.25 kWth and were designed to operate respectively with R410A and R22.

Based on the assumption that manufacturers can address performance losses, the increased discharge temperatures and safety concerns associated with flammable alternatives, the ORNL concludes that all the low-GWP alternative refrigerants “may be considered as prime candidate refrigerants for high ambient temperature applications”.