ASHRAE Journal - June 2024 - 42

FEATURE
in engines and the estimation of
absolute zero.
Carnot's association with
Clément and Desormes followed
his connection through the École
Polytechnique with several of
France's other leading scientists and
philosophers, including Jacques
Charles, Joseph Gay-Lussac, AndréMarie
Ampère, François Arago and Siméon Poisson.
In 1824, following fi ve years of study under Clément
and Desormes, Sadi Carnot published a volume
describing a thought experiment he had devised.
This was Réfl exions sur la puissance motrice du feu et sur les
machines propres à développer cette puissance, or in English,
Refl ections on the Motive Power of Fire and on Machines Fitted
to Develop that Power. It was a mental stroll through the
inconsistencies and discontinuities that Carnot saw in
scientifi c thinking about heat. It is a kind of thinking
aloud, where he starts by listing the things that we
don't know, making it clear that these thoughts have
not previously been expressed and therefore he lacks
vocabulary to describe them.
Rather than trying to analyze the best performing
EARLY STUDIES The École Polytechnique is
now 230 years old.
machines of the time, he envisages
an ideal machine, operating
across infi nitesimal temperature
differences and entirely
hypothetical. He then develops his
ideas, creating insights along the
way, and leading to the conclusion
that steam engines are bound to
be ineffi cient because they operate
between temperatures of about 160°C (320°F) as the
source and 40°C (104°F) as the sink, whereas the coal
providing the heat is burning at over 1000°C (over
1,800°F) and therefore the majority of the height of the
heat's fall is unproductive. This leads him to conclude
that high pressure steam engines are necessary
and therefore three or four stages of expansion are
required to improve effi ciency (Read more at https://
tinyurl.com/JournalExtras).
To reach these conclusions he quotes many French,
English and German scientifi c publications showing
that he was well-versed in the literature, including
up-to-date papers by Humphrey Davy, Michael Faraday
and John Dalton in England as well as Gay-Lussac,
Clément and Desormes, among others in France.
The Many Facets of Sadi-Quotations from His Personal Notebooks1
SADI THE POLITICIAN
SADI THE SOLDIER
" To each conqueror can be said, when he
has ceased tormenting our poor globe,
'Would you not have been able to tilt equally
well against a little globe of pasteboard?' "
" The laws of war, do they say? As if war
were not the destruction of all laws. "
SADI THE PHILOSOPHER
" Never turn to the past unless to
enlighten the future. "
" Speak little of what you know, and not
at all of what you do not know. "
" Why not say more frequently
'I do not know'? "
SADI THE OPTIMIST
" I rejoice for all the misfortunes which
might have happened to me, and
which I have escaped. "
" Let us not be exacting;
perfection is so rare. "
42
" Never direct an argument against
anyone. If you know some particulars
against
your adversary, you have a right to
make him aware of it to keep him under
control, but proceed with discretion,
and do not wound him before others. "
" When discussion degenerates
into dispute, be silent; this is not to
declare yourself beaten. "
SADI THE ECONOMIST
" All changes in taxes should, as a general
thing, be made gradually, in order to avoid
sudden changes of fortune. "
" According to the system of modern
economists, it would be desirable that the
government should interfere as little as
possible in the commerce and industry
of the country. Nevertheless we cannot
deny that in certain circumstances this
intervention is very useful. "
ASHRAE JOURNAL ashrae.org J U N E 2 0 2 4
SADI THE FRIEND
" Why try to be witty? I would rather be
thought stupid and modest than witty and
pretentious. "
" Abstain from all pleasantry
which could wound. "
SADI THE SPORTSMAN
" Vary the mental and bodily exercises
with dancing, horsemanship, swimming,
fencing with sword and with sabre,
shooting with gun and pistol, skating,
the sling, stilts, tennis, bowls, hop on one
foot, cross the arms, jump high and far,
turn on one foot propped against the wall,
exercise in shirt in the evening to get up a
perspiration before going to bed, turning,
joinery, gardening, reading while walking,
declamation, singing, violin, versifi cation,
musical composition, eight hours of sleep,
a walk on awakening, before and after
eating, great sobriety, eat slowly,
little and often, avoid idleness and
useless meditation. "
WIKIMEDIA COMMONS, GALLICA.BNF.FR
https://tinyurl.com/JournalExtras https://tinyurl.com/JournalExtras http://www.ashrae.org
ASHRAE Journal - June 2024

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