USA: The flammable refrigerant R32 could be an attractive low-GWP solution for mainstream air-conditioning and heat pump applications with performance comparable to R410A, according to latest research.
The research carried out by Hung Pham and Rajan Rajendran of Emerson Climate Technologies evaluated the potential for the mildly flammable, A2L-rated, R32 and the HFOs 1234yf and 1234ze in air conditioning systems. It came out in favour of R32 in terms of both efficiency and cost as a suitable replacement for R410A.
R32 has theoretically 3-14% higher capacity in the air conditioning evaporating operating range (45-55°F) and 7-16% higher capacity in the heat pump evaporating operating range (-10° - 30°F). Correspondingly, R32 has theoretically -1% to +5% higher EER in the air conditioning cooling operating range and 0% to 7% higher EER in the heat pump heating operating range.
In practical drop-in tests in R410A systems, the actual relative compressor capacity was seen to have on average about 3-4% lower than theoretical the actual relative compressor EER was on average about 2-3% lower than theoretical due to lower overall isentropic efficiency.
The authors point out, however, that these tests were conducted using an R410A optimized compressor and not a R32 optimized product. Optimizing the compressor and system for R32 could push the refrigerant towards achieving its theoretical potential as well as mitigating its higher compressor discharge temperature.
The report states that the natural refrigerants CO2 and propane have so far have not shown to be cost-effective solutions for mainstream air conditioning due to their low efficiency and/or A3 flammability safety reasons. R290 is limited to much smaller units such as <1-ton mini splits where the charge can be limited closer to 150g that has become accepted as a standard without requiring secondary loop.
The authors maintain that R32 could serve as the initial candidate for new equipment to meet any potential HFC phase down proposal for at least until 2020+.
The HFO's, however are hampered by their relatively high costs but no visible advantages over R32 were observed in these early drop-in system test results. The HFO blends are comparable to R32, but their use may be limited initially until their cost position becomes clearer, says the report.
http://www.emersonclimate.com/en-us/Documents/R32_and_HFOs_as_Low-GWP_Ref_for_AC.pdf