ASHRAE Journal - June 2024 - 72

REFRIGERATION APPLICATIONS
COLUMN
Andy Pearson
Great Balls of Fire!
BY ANDY PEARSON, PH.D., C.ENG., FELLOW ASHRAE
My father, Dr. S. Forbes Pearson, known to everyone as Forbes, died in March of this
year. At his memorial service in April, I reflected on the fact that there are at least half
a dozen things that are now commonplace in the industrial refrigeration world but
that had not been done, or at least had not been commercialized, until he did them.
I likened this to a backroom songwriter who creates
a tune for someone else and then hears it all over the
place-on the radio, in a pub or a football stadium-
without anyone connecting him to the music that they
love so much. I was thinking of someone like American
songwriter Otis Blackwell. Otis who? Well, he's only the
guy who wrote " All Shook Up, " " Return to Sender " and
" Don't Be Cruel " for Elvis, and of course " Great Balls of
Fire " for Jerry Lee Lewis.
I wrote about one of the innovations commercialized
by Forbes in last month's column: reverse
cycle defrost. Two of his other innovations
relate to the use of carbon dioxide (CO2) as
a refrigerant. CO2 as a volatile secondary
refrigerant, where the circulating coolant
evaporates and recondenses without
a compressor, was first done for a
supermarket installation in Kilmarnock,
Scotland, in 1991 and has subsequently
been used for chill stores, air-conditioning
systems and blade server cooling around
the world. The concept of parallel compression was
developed in 2003 for single compressor applications
in transcritical systems to improve capacity and
efficiency in warm weather, although it is now
much more commonly used in multiple compressor
systems-a much easier proposition!
One of the most widely commercialized ideas led by
Forbes, among others, was the use of zeotropic mixtures
in refrigeration systems. This work in the 1980s
was done in parallel with several other researchers,
particularly in America. This led to lifelong friendships
with many of them, including Dave Didion of National
Bureau of Standards (which later became NIST) and
Don Bivens of the DuPont Company. The insight that
Forbes brought to this work was invaluable. He knew,
72
ASHRAE JOURNAL ashrae.org J U N E 2024
for example, that a good service technician, when
faced with oil return problems in an industrial R-22
system, might add a small amount of R-12 to improve
miscibility, even though the boiling points of the two
refrigerants were very different.
Searching for a substitute for R-502 in the mid-1980s,
His inventions are enjoyed by
millions.
Forbes decided to add some propane to R-22 in order
to improve oil return in the same way and set up his
own " great balls of fire " to establish how much propane
would make the mixture flammable. " Hardly any " was
the disappointing answer following a series
of flammability tests, but by adding a third
component, R-218, he managed to get the
propane proportion of his blend up to 5%
without the mixture being flammable.
The realization that mixing components
could provide beneficial characteristics
was a game-changer. The hydrocarbon
improved oil compatibility and the
perfluorocarbon, as well as providing some
fire suppression, gave an extremely low
discharge temperature, which was an essential factor in
the replacement of R-502.
There are now over 100 recipes for zeotropic blends
following this principle registered with ASHRAE SSPC
34, and we have all learned that temperature glide
does not prevent systems from operating reliably and
efficiently.
Forbes believed firmly in sharing information,
reckoning that he always gained more than he gave in
these exchanges. Any invention, whether technical or
musical, starts out as your own private thought but with
the hope that it will become public property; enjoyed by
millions to whom its origins are unknown.
Andy Pearson, Ph.D., C.Eng., is group managing director at Star Refrigeration in
Glasgow, UK.
PHOTO COURTESY OF THE AUTHOR
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ASHRAE Journal - June 2024

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