R744 is a refrigerant grade of CO2 gas. It's a natural refrigerant that's very efficient and has a low global warming potential (GWP) of just 1. It's also non-toxic and non-flammable, meaning it's classified as a safety group A1 refrigerant.
R744 (CO2) is refrigerant grade CO2, used as a replacement for R134a and R404A in ultra-low, low and medium-temperature refrigeration applications.
Compared with other refrigerants CO2 operates at higher pressures which means component costs are higher and there is leak potential. Also, it is not preferable for very hot climates since it mostly operates in supercritical phase, which is not efficient for refrigeration.
An experimental based exergetic comparison between R744 and R134a refrigeration cycles. Substitution of R134 with R744 working in a transcritical cycle. Optimization of the transcritical cycle exergetic performances. The exergetic performances of R134a are better than that of R744 (from +20 to +44%).
No. R744 operates on pressures up to ten times higher than R134a. Although it has been used for some time in stationary equipment, developing R744 systems for automotive applications has been a significant engineering challenge, with unique components and system layouts required for this refrigerant.
Maintenance Complexity: The high pressures involved mean that maintenance and repair tasks can be more complex and require specialized knowledge and tools, potentially leading to higher service costs.
Possible alternatives to R-134a
Attention is increasingly focused on low-GWP refrigerants that are hydrofluoroolefins (HFO). R-1234yf in particular is often seen as a possible alternative to R-134a. The GWP value of R-1234yf is 4, which means it has a very low global warming potential.
R744 (CO2) was first adopted by Mercedes in the S-Class in 2017, although it has since dropped this approach. VW's ID EVs on the MEB platform use R744 in models that have a heat pump. R744, by definition, has a GWP of 1.
CO2 (R744)
Exempt from the Section 608 venting prohibition, meaning it is legal to knowingly release this refrigerant to the environment; however, CO2 is not exempt from the Section 609 requirements such as use of certified refrigerant handling equipment.
According to its manufacturer, Chemours, use of R-1234yf has grown so much since the refrigerant replaced the long-established R-134a that it's now used in 95% of new cars sold in the U.S. An estimated 220 million cars on global roads are also using it.
With zero ODP, R744 refrigerant won't contribute to the depletion of the ozone layer. No PFAS. Unlike synthetic refrigerants, R744 won't pollute groundwater with harmful 'forever chemicals.
Although R-744 is non-flammable, its high pressures, toxicity in high concentrations and potential for dry ice formation must be considered when applying and handling it.
Ammonia is an efficient refrigerant used in food processing and preservation, as well as many other refrigeration and air-conditioning processes. Ammonia has desirable characteristics as a refrigerant, which have been well known for over a century. It is corrosive and hazardous when released in large quantities.
However, R-744 is unlikely to be used as a refrigerant in some applications because of its high working pressure. This creates challenges in the design and operation of refrigeration systems and can increase costs.
R744 requires systems and service equipment that are more durable than those used for R1234yf and R134a due to the high operating pressures. R744 service equipment, which vents used refrigerant to atmosphere, has integrated fans to disperse the refrigerant.
RPE-744-85. Summit RPE-744 Series is a fully synthetic polyolester lubricant specifically designed for use in refrigeration compressors using carbon dioxide (R744) as the refrigerant. RPE-744-Series is miscible with carbon dioxide and offers superior hydrolytic stability and corrosion resistance.
The Intergovernmental Panel on Climate Change has since added R-134A to its list of greenhouse gases, declaring definitively that this refrigerant is a poor choice for the future of the planet and its inhabitants.
All CFCs and HCFCs must be recovered before opening a system for service or disposing of appliances. The need to conserve or recover refrigerant has led the industry to develop a specific terminology defined by three R's: Recovery, Recycling and Reclaiming.
R-134a is an HFC refrigerant and cannot be vented under the Venting Prohibition because it is a non-exempt substitute of CFCs and HCFCs. Question #8 Nitrogen can be used to pressurize or blow debris out of a system containing a half charge of refrigerant.
Air conditioner and heat pump manufacturers are rolling out new refrigerants to comply with EPA guidelines. Starting in January 2025, no new HVAC systems will use R-410A refrigerant. Instead, most residential systems will use either R-32 or R-454B refrigerant, both of which have a comparably lower environmental impact.
Key features of R744 refrigerant include: Non-corrosive, non-toxic, and non-flammable.
The US EPA is to ban a host of high GWP refrigerants including R404A, R134a, R407C and R410A in certain new products from as early as January 1, 2021.
R744 (CO2) is refrigerant grade CO2, used as a replacement for R134a and R404A in ultra-low, low and medium-temperature refrigeration applications. R744 (CO2) is becoming increasingly popular due to its excellent properties.
There are three refrigerants that can be used to replace R-134a: R-1234yf, R-152a, and R-744.