26 Product Developments New low GWP refrigerant blends
The refrigeration and air conditioning industries are in a state of flux. Increased focus on the potential environmental impact of these technologies has led to regulations that will impact on the use of HFC refrigerants. Stuart Corr of Mexichem explains.
IN THE EU, the use of refrigerants with GWP greater than 150 in new automotive air conditioning systems is controlled by the MAC Directive, while the upcoming changes to the F-Gas Regulation will impose restrictions on particular end uses and on the maximum quantities of HFCs that may be placed on the market in Europe.
The fluorochemical manufacturers and others have been active in the development of reduced GWP alternatives to the traditional HFCs in order to respond to environmental concerns and to allow society to continue to benefit from the use of cooling and heating technologies based on fluorochemical refrigerants. While refrigerant GWP is a clear focal point for the development of alternatives, we need to ensure that the alternatives are at least as energy efficient in use than the fluids they are intended to replace if we are to truly decrease the environmental impact of the use of refrigeration, air conditioning and heat-pump technologies. The family of unsaturated
hydrofluorocarbons, or ‘hydro-fluoro- Characteristic refrigerant properties
olefins’ (HFOs) have received considerable attention in this quest for alternatives. Of this family, two candidate molecules with appropriate boiling points have been identified as being of particular interest to the development of alternative refrigerants – R1234yf and R1234ze.
Both of these fluids are classified as A2L under ASHRAE Std34 and are mildly flammable.
R1234yf has been extensively investigated as a fluid to replace R134a in automotive air conditioning systems but while R1234yf offers a good technical solution, it is likely to remain more expensive than R134a even at a mature production scale.
Mexichem has been investigating the potential of a refrigerant, R1234ze in both automotive and stationary applications. A combination of good thermodynamic properties, the potential for favourable production costs and significant installed production capacity make this an attractive material on which to base a range of refrigerant blends to address the needs of a variety of application end uses.
Alternative fluids
While the automotive sector has broadly accepted the use of a mildly flammable refrigerant, for example R1234yf, this may not be possible in other application areas. Further, the boiling points of R1234yf and R1234ze are such that they are less than ideal for use in applications that traditionally use R410A or other low- boiling refrigerants such as R404A. To meet these needs, Mexichem has developed and tested a number of blended refrigerants as potential alternatives to R134a and other HFCs in a range of applications.
R134a automotive alternatives Mexichem has two development blends for automotive applications, R444A (AC5) and R445A (AC6). Like R1234yf, both fluids have GWP below 150 in order to comply with the EU MAC Directive and both are classified as A2L under ASHRAE-34. R444A is a blend of R32, R152a and R1234ze, R445A is a blend of R744, R134a and R1234ze. R444A is of comparable flammability to R1234yf while R445A is non-flammable at ambient temperature, becoming flammable at elevated temperatures but has particular handling requirements.
Both R444A and R445A have been the subject of intensive investigation over the last few years under the auspices of an SAE Cooperative Research Program (CRP MRB) involving many of the global major automotive manufacturers, their Tier-1 air conditioning system manufacturers and third-party research houses.
Data and reports of this CRP conclude that both fluids are viable alternatives to R134a in automotive air conditioning systems.
R134a stationary sector alternatives Clearly, the fluids developed for use in automotive air conditioning will also have potential to be used in those stationary sectors where GWP below 150 is required under F-Gas but not all stationary applications have such a GWP limitation giving some latitude for formulation development to meet the needs of this diverse sector. This flexibility is required in order to formulate non-flammable (A1) fluids and to match the behaviours of a range of existing HFCs. Mexichem’s non-flammable developmental refrigerants include: ■ AC5X, a blend of R32, R134a and R1234ze with GWP of 620 has been formulated to be a non-flammable
ACR News May 2014 Visit ACR News online at
www.acr-news.com
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