ACR Journal

October 2022 | November 2022 Natural refrigerants such as CO 2 have been used in refrigeration systems since the 1850s, but the advent of synthetic refrigerants and in particular CFCs led to its use being limited to certain applications. In the mid-20th century, however, it was found that CFCs were harmful to the ozone layer and as a result the Montreal Protocol was created to phase out the use of substances with high Ozone Depleting Potential (ODP), which led to the rise in use of non or low ODP HFC refrigerants. These refrigerants, or F-gases, while less harmful to the ozone layer were found REFRIGERANTS 20 Hayley Cattell, group sales director of Beijer Ref UK & Ireland, explores the potential of CO 2 refrigeration and explains why the new Beijer Ref Academy can help engineers with the transition to natural refrigerants. Making the move to natural alternatives to be contributing significantly to global warming and the Montreal Protocol was amended in Kyoto to limit and reduce their use. The EU then created the original F- Gas Legislation in 2006 to control the phase out of high GWP refrigerants through bans and quota limitations (based on CO 2 e) which has seen a significant rise in the use of natural refrigerants (CO 2 , ammonia, hydrocarbons) and new refrigerants with low or lower global warming potential (GWP) being created. The UK remains fully aligned to the F-Gas legislation and the EU may introduce faster phase downs in 2024, with the UK carrying out a similar review. The table below left details some of the refrigerants currently on the market and their key properties. The data demonstrates that there is no single answer to the question of how we lower overall GWP, but there are certainly options: Carbon dioxide (CO 2 ) has the refrigerant designation R744 and has experienced a resurgence as a refrigerant in commercial and industrial applications. While R744 can be an excellent refrigerant, using it is not without challenges and systems need to be carefully designed and operated. Although it is not subject to the F-Gas regulation, and is not flammable, it operates at higher pressures than other commonly used refrigerant. Further key considerations associated with CO 2 include: • It is a naturally occurring gas that exists in the atmosphere • It has a global warming potential (GWP) of 1 • It has a low critical point (31°C, 72.6 Bar gauge) • It has a high triple point (-56.6°C, 4.2 Bar gauge) Hayley Cattell Volume 8 No.6 Refrigerant Family GWP Safety Group Application Used in Longevity R404A HFC 3922 A1 MT/LT Banned over 10kg None RAA8A HFC Blend 1387 A1 MT/LT Commercial Refrigeration Short- Medium R32 HFC 677 A2L MT Air Conditioning Medium R455A HFO Blend 146 A2L MT/LT AC & Commercial Ref Long R1234ze HFO 7 A2L MT Vehicle AC Long R290 (Propane) HC 3 A3 MT/LT Integral Systems Long R744 (CO2) Natural 1 A1 MT/LT Commercial & Industrial Ref Long R717 (NH3) Natural 0 B2L MT/LT Industrial Ref Long