Page 24 - Entrophy Analysis in Thermal Engineering Systems

Birth and evolution of thermodynamics 15

This law is credited to Jacques Charles as its discoverer in 1787, although his
work was not published. Later, Dalton and Gay-Lussac conducted experi-
ments with air and other gases, which confirmed the law given by Eq. (2.2).

2.2.3 Experiments of Rumford and Davy
The notion of materiality of heat and thus the caloric theory was invalidated
by Count Rumford in 1798 and Humphry Davy in the following year. Tait
regarded Rumford and Davy as the true discoverer of the first law of ther-
modynamics whose contribution was unnoticed until Joule re-established
the law through a series of comprehensive experiments [4].
As the superintendent of the cannon boring in the workshops of military
arsenal at Munich, Rumford noticed a considerable amount of heat gained
by a brass gun that was bored in a short time. In his communication to the
Royal Society, he presented the details of four experiments, which led him
to question:

What is heat? Is there any such thing as an igneous fluid? Is there anything that can
with propriety be called caloric? We have seen that a very considerable quantity of
heat may be excited in the friction of two metallic surfaces and given off in a con-
stant stream or flux, in all directions, without interruption or intermission, and with-
out any signs of diminution, or exhaustion … it appears to me to be extremely
difficult, if not quite impossible, to form any distinct idea of anything, capable
of being excited, and communicated, in the manner the heat was excited and
communicated in these experiments, except it be motion [5].

The experiment of Davy consisted of two pieces of 6 2 ⅔ in. ice, which

were rubbed together and then almost entirely melted. He wrote: “The
fusion took place only at the plane of contact of the two pieces of ice, and no bodies
were in friction but ice. From this experiment it is evident that ice by friction is
converted into water, and according to the supposition [of materiality of heat] its capac-
ity is diminished; but it is a well-known fact, that the capacity of water for heat is much
greater than that of ice; and ice must have an absolute quantity of heat added to it,
before it can be converted into water. Friction consequently does not diminish the capac-
ities of bodies for heat.” From this argument, Davy concluded the immateriality
of heat. He then elucidated that “Heat … may be defined a peculiar motion, prob-
ably a vibration, of the corpuscles of bodies … It may with propriety be called the
repulsive motion” [6].

Tait, in appraising the works of Rumford and Davy, writes: “Notice how
distinctly these two great leaders were men who based their work directly upon exper-
iment. There is no a priori guessing, or anything of that kind, about either Rumford’s