Correlating the speed of sound with the Gibbs energy and estimating the
speed of sound in fatty acid methyl ester and biodiesel
Abstract
The relation between the speed of sound (u) in biodiesel and the change
in Gibbs energy (G) has not been described in the literature. With the
method of Gibbs energy additivity, the relation between u and G can be
expressed as ln(u2) = G/RT + A, where R is the universal gas constant,
T is the absolute temperature, and A is a constant. Further expansion of
G into its enthalpy and entropy, and sub-dividing the molecule of a
fatty and methyl ester (FAME) into groups of atoms, the final model is
good for estimating the speed of sound in both FAME and biodiesel at
various temperatures. Only the numbers of double bonds and carbon atoms
of the fatty acid are required for the calculation.