HFO/HFC/CO2 hybrid on its way

USA: A new lower GWP replacement for R404A, which blends an HFO and an HFC with a “natural” refrigerant is to be made commercially available next year.

The unusual refrigerant blend, R455A, which developer Honeywell has been keeping under wraps, is being considered for ASHRAE classification as an A2L “mildly flammable” gas.

Honeywell has confirmed that the refrigerant, which it will be marketing as Solstice L40X, consists of 75.5% HFO R1234yf, 21.5% R32 and 3% CO2.

Said to be tailored for hermetic reciprocating compressors in MT and LT, its original planned application was for use as a low GWP replacement for R404A in condensing units. However, it is known that it is also being tested in stand-alone refrigeration equipment. Pastorfrigor, the Italian display equipment manufacturer, featured a unit running on the new gas at last month’s HOST exhibition in Milan.

A Honeywell spokesman confirmed that R455A was one of the developmental refrigerants it is working on with major components manufacturers and OEMs. The spokesman also confirmed that Pastorfrigor had been running preliminary tests in a non-optimised chiller cabinet originally designed for R407F (Honeywell’s lower GWP (1824) R404A replacement blend marketed as Performax LT). The performance of R455A was said to match R407F in the Pastorfrigor tests and exhibit a lower discharge temperature of an average of 8°C. Pastorfrigor is to start full tests in the near future.

For obvious commercial reasons, refrigerant developers are not keen to reveal too much about the new blend as yet, but Honeywell has told the Cooling Post that R455A matches the capacity of R404A and has the same or better efficiency. Glide is thought to be around 6K.

On the face of it, the addition of a small amount of the “natural” refrigerant CO2 makes this blend an unusual one, but it is known that Honeywell and others have been working with different blends containing CO2 for a number of years. The CO2 is thought to boost system capacity.

Originally developed under the codename HDR 110, R455A’s GWP of 145 places it in the “mildly flammable” category. Mindful of this, Honeywell has previously admitted upcoming standard updates could potentially enable such refrigerants to be used in small self-contained refrigeration systems.

Test results from its application in a single door reach-in freezer were the subject of a paper presented by Honeywell at the Purdue University compressor conference last year. The R404A freezer had an internal volume of about 700 litres and rated capacity of around 560W. The top-mount self-contained refrigeration unit had a nominal charge of 354g of R404A and comprised a 1/2hp hermetic compressor, air-to-refrigerant tube-in-fin condenser and evaporator, suction-line liquid-line heat exchanger and thermostatic expansion valve.

Initial drop-in tests showed that R455A had capacities below 90% of baseline tests with R404A and a slightly lower efficiency. However, when the original parallel-flow evaporator was altered to a counter-flow arrangement and the expansion valve adjusted to allow for R455A’s slightly lower pressure, the unit showed a 6% lower energy consumption and a near match in capacity.

Related stories:

R404A replacement blends HFCs with CO2 – October 6, 2015
USA: ASHRAE is proposing to list a new low GWP R404A refrigerant replacement blend comprising an HFC, an HFO and CO2. Read more…

Honeywell tests new R404A replacement – July 29, 2014
USA: Honeywell has been testing a new low GWP refrigerant as a potential replacement for R404A in hermetically-sealed refrigeration systems. Read more…