REFRIGERANTS
Understanding flammability
A $5.2m grant has been provided to fund a research programme on flammable refrigerants by the US Department of Energy, ASHRAE and AHRI. Here, Stuart Corr, techno commercial director of refrigerant manufacturer and supplier Mexichem, discusses why this research is important for the refrigeration and air conditioning industry.
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It is to be hoped that this new grant can make an important contribution to helping incorporate 2L refrigerants into updated
standards and codes governing the use of refrigerants in the US and across the globe.
he new collaboration between the US government Department of Energy (DOE) and the trade bodies American Society of Heating Refrigeration and Air Conditioning Engineers (ASHRAE) and Air Conditioning, Heating and Refrigeration Institute (AHRI) will fund an investigation into the use and properties of mildly flammable (2L) refrigerants, including HFOs, R32 and flammable (A3) hydrocarbon refrigerants. The DOE is the largest contributor to the project, providing $3m. ASHRAE and AHRI are contributing $1.2m and $1m to the project. While ASHRAE has funded hundreds of research projects into refrigerants, this announcement marks its largest ever single transfer from their Research Reserve Fund. This is a valuable recognition of the growing importance that 2L fluids will play in meeting targets for adoption of low GWP refrigerants.
Research into low GWP refrigerants has partly come about through regulatory restrictions. In the US, refrigerant use is controlled by the US EPA’s SNAP regulations. There are regulations in Europe on both mobile air conditioning equipment through the MAC Directive and stationary equipment through the F-Gas Regulations. The MAC Directive has banned the use of refrigerants with a GWP over 150 in automotive air-conditioning systems, and the F-Gas Regulations have placed restrictions on refrigerant maximum GWP across a range of applications – for example, refrigerants with a GWP over 150 for new supermarket multipack systems from 2022. As a result of these regulations and other factors, industry is looking to develop lower GWP alternatives.
New refrigerants are classified according to both their toxicity and flammability. The most well established classification for this is the ASHRAE classification. Refrigerants such as R410A, R407A and R404A are class 1 in their flammability, so do not show flame propagation when
48 August 2016
tested at 100°C and 101.3kPa in air. Class 2 refrigerants are those with flammability lower than 0.10kg/m3
at 100°C and
101.3 kPa and a heat of combustion of less than 19kJ/kg. Class 3 refrigerants have flammability over this boundary and this includes many hydrocarbons.
Many of the reduced GWP refrigerants of interest fall into the 2L flammability category — a subclass of class 2 with a burning velocity of less than 10cm/s — reflecting their reduced flammability. This category was introduced in 2010 and includes refrigerants such as R32, NH3
, R1234yf, and
R1234ze. At the present time, it is likely that the lowest GWP products appropriate for many application end-users will be flammable to a degree, and likely classified as 2L. Many industrial applications currently rely on non- flammable refrigerant fluids and transition to adopting a flammable fluid, even a 2L fluid, would pose significant risk- mitigation expenditure if even possible.
Further, the lack of recognition of 2L in current regulations presents a significant limitation for understanding the implementation of these refrigerants. This is an area that requires more research and it is to be hoped that this new grant can make an important contribution to helping incorporate 2L refrigerants into updated standards and codes governing the use of refrigerants in the US and across the globe.
This last point is crucial, as at present a number of countries and regions, including Europe, have regulations that prohibit the use of flammable refrigerants in many applications. Although 2L refrigerants are less flammable than another group of low GWP alternatives — the hydrocarbons — some countries still severely restrict their use. In some circumstances this is in large part because of the lack of regulatory recognition of the reduced- flammability 2L class at this point in time; fluids are broadly classified as flammable or non-flammable.
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