ASHRAE Journal - April 2015 - 80

COLUMN REFRIGERATION APPLICATIONS
Andy Pearson

English, Irish and Scots
BY ANDY PEARSON, PH.D., C.ENG., MEMBER ASHRAE

Three pioneers of engineering science have been immortalized through the use of their
names as units in the SI system, representing energy, temperature and power. They are
James Joule, James Watt, and William Thomson (Lord Kelvin) and it is likely every practicing refrigeration engineer, designer, technician and mechanic uses at least one of their
names every day of their working lives. They create an interesting weave in space-time.
first reading of his theories, at a meeting of the British
Watt and Kelvin worked in the same cramped, oldAssociation for the Advancement of Science in 1843, was
fashioned and dingy university laboratories in Glasgow,
Scotland, but were not contemporaries-Watt left Glasgow met with complete silence from the audience. He was
24 years old. Despite this setback he persevered with his
to settle in Birmingham, England, 50 years before Kelvin
experiments into electromagnetism and heat, presenting
was born. Watt and Joule's lives overlap, but only by eight
further papers to the British Association in 1845 and 1847.
months, and Watt was nearly 83 when Joule was born.
The latter meeting was attended by William Thomson,
Kelvin and Joule, although separated by more than 200
recently appointed as Professor of Natural Philosophy at
miles, worked on the same mathematical and physical
Glasgow at the age of 23. Thomson was initially skeptical
problems and had a strong friendship based on mutual
because Joule's ideas were so unlike conventional
respect and frequent letter-writing.
Never, never, never give in. thinking, but he noted that Joule's theory helped
James Joule, the Englishman in this trio of
explain some shortcomings of traditional caloric
famous names, was born in Salford, just souththeory and over the next four years he convinced
west of Manchester, England, in 1818. His father
himself that Joule's reasoning was correct. Joule
owned a brewery and Joule was raised and eduand Thomson started a series of experiments
cated to take over the business, being tutored by
to validate Joule's theory. Their correspondence
John Dalton who is famous for creating Dalton's
extended from 1852 to 1856, and Joule continued
law of partial pressures (also widely used by
Winston Churchill
stirring and measuring for a further 20 years.
refrigeration technicians, whether they realize
Joule was not the only one to develop these ideas; similar
it or not). Joule developed a passion for science, particuthinking surfaced at about the same time in Germany and
larly topics that affected his working life such as electricDenmark, but above all others Joule stuck to his task, even
ity, heat and power. He was a businessman and indusin the face of stony opposition. He continually refined
trialist who pursued science as a hobby, and his wealthy
his techniques and measurements, perfecting his craft
background and successful brewery business provided
and homing in on the elusive value of equivalence. The
the means to follow his amateur enthusiasms.
number he was seeking was the amount of mechanical
He created sophisticated scientific experiments that
work, measured in foot-pounds, that was required to heat
were completely at odds with the received wisdom of the
one pound of water from 60°F to 61°F (15.56°C to 16.11°C).
establishment at the time and he claimed, for example,
When he died in 1889 his tombstone was inscribed with
to be able to measure temperature to within 0.005°F
the value "772.55," this being, in his opinion, his most
(0.0028°C); an accuracy that would not be out of place in
accurate assessment, achieved in 1878 after 35 years of
a modern, digital, science laboratory. The main goal of all
testing. The fact that this is within one percent of the true
his experimentation was to demonstrate that mechanivalue of 778.17 ft·lb/Btu (4,187 Nm to raise 1 kg by 1 K) is tescal work could be converted to heat and to establish the
tament to Joule's precision, his patience and his eyesight.
conversion factor; the so-called "mechanical equivalent
of heat." Although this seems normal to us, it was so far
Andy Pearson, Ph.D., C.Eng., is group engineering director at Star Refrigeration in Glasgow, UK.
removed from scientific orthodoxy at the time that the
80

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