Identifying refrigerant fluids with low 'global warming potential'

Sep 19, 2012 by Laura Ost
Refrigerant Fluids. Credit: Kazakov/NIST

(Phys.org)—Researchers at the National Institute of Standards and Technology (NIST) have developed a new computational method for identifying candidate refrigerant fluids with low "global warming potential" (GWP)—the tendency to trap heat in the atmosphere for many decades—as well as other desirable performance and safety features.

The NIST effort is the most extensive systematic search for a new class of refrigerants that meet the latest concerns about climate change. The new method was used to identify about 1,200 promising, low-GWP chemicals for further study among some 56,000 that were considered. Only about 60 of these have boiling points low enough to be suitable for common refrigeration equipment, an indication of how difficult it is to identify usable fluids.

The ongoing NIST project is a response to U.S. industry interest in a new generation of alternative refrigerants that already are required for use in the European Union.

The refrigerants now used in cars and homes are mainly hydrofluorocarbons (HFCs). They were adopted a generation ago in the effort to phase out (CFCs), which deplete the . An example is R-134a (1,1,1,2-tetrafluoroethane), which replaced ozone-depleting chemicals in automobile air conditioners and home refrigerators. R-134a now is being phased out in Europe because HFCs remain in the atmosphere for many years, yielding a high GWP. A compound's GWP is defined as the warming potential of one kilogram of the gas relative to one kilogram of carbon dioxide. R-134a has a GWP of 1,430, much higher than the GWP of 150 or less now mandated for automotive use in Europe.

Promising low-GWP chemicals include fluorinated , which react rapidly with and thus will not persist for long periods.

"What industry is trying to do is be prepared, because moving from a GWP in the thousands or tens of thousands to a GWP of 150 is an enormous challenge, both economically and technologically," says NIST chemist Michael Frenkel. "We decided to leverage the tools NIST has been developing for the last 15 years to look into the whole slew of available chemicals."

The affected industry is huge: The U.S. air conditioning, heating and refrigeration equipment manufacturing industry ships about $30 billion in goods annually, according to the U.S. Bureau of the Census.

NIST has extensive experience evaluating alternative refrigerants, having previously helped the refrigeration industry find replacements for CFCs.

The new NIST method estimates GWP by combining calculations of a compound's radiative efficiency (a measure of how well it absorbs infrared radiation) and atmospheric lifetime, both derived from molecular structure. Additional filtering is based on low toxicity and flammability, adequate stability, and critical temperature (where the compound's liquid and gas properties converge) in a desirable range. The method was applied to 56,203 compounds and identified 1,234 candidates for further study. The method, which was validated against available literature data, is accurate and fast enough for virtual screening applications. The approach is similar to the large-scale virtual screening and computational design methods for discovering new pharmaceuticals.

The screening is the initial stage of a larger study funded by the U.S. Department of Energy. The next step will be to further narrow down the candidates to a couple dozen suitable for detailed investigation in refrigeration cycle modeling.

Explore further: A smart prosthetic knee with in-vivo diagnoses

More information: A. Kazakov, M.O. McLinden and M. Frenkel. Computational design of new refrigerant fluids based on environmental, safety, and thermodynamic characteristics. Industrial and Engineering Chemistry Research. Article ASAP, Publication Date (Web): September 4, 2012. DOI: 10.1021/ie3016126

Related Stories

Scientists discuss carbon dioxide uses

Mar 13, 2006

The use of environmentally friendly carbon dioxide as a refrigerant instead of ozone-depleting chemicals will be discussed at Purdue University this week.

NIST releases major update of popular REFPROP database

Apr 13, 2007

The National Institute of Standards and Technology has released an expanded and upgraded version of a popular database, a computer package for calculating the properties and modeling the behavior of fluids.

Recommended for you

A smart prosthetic knee with in-vivo diagnoses

Apr 22, 2014

The task was to develop intelligent prosthetic joints that, via sensors, are capable of detecting early failure long before a patient suffers. EPFL researchers have taken up the challenge.

Old tires become material for new and improved roads

Apr 22, 2014

(Phys.org) —Americans generate nearly 300 million scrap tires every year, according to the Environmental Protection Agency (EPA). Historically, these worn tires often end up in landfills or, when illegally ...

Students take clot-buster for a spin

Apr 21, 2014

(Phys.org) —In the hands of some Rice University senior engineering students, a fishing rod is more than what it seems. For them, it's a way to help destroy blood clots that threaten lives.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

antialias_physorg
5 / 5 (1) Sep 19, 2012
Only about 60 of these have boiling points low enough to be suitable for common refrigeration equipment


Well, they can stop searching, because the next generation of refrigerators might just use water (and magnets) if this works as described
http://sciencenor...ill-half

...and they won't have that intermittent buzzing noise from the pumps, either.

More news stories

Is nuclear power the only way to avoid geoengineering?

"I think one can argue that if we were to follow a strong nuclear energy pathway—as well as doing everything else that we can—then we can solve the climate problem without doing geoengineering." So says Tom Wigley, one ...

Cyber buddy is better than 'no buddy'

A Michigan State University researcher is looking to give exercise enthusiasts the extra nudge they need during a workout, and her latest research shows that a cyber buddy can help.