A new entropy function to analyze isentropic processes of ideal gases with variable specific heats
Özet
A new entropy function s
+
is defined in terms of the existing entropy function s
◦ and
temperature as s
+ = s
◦ − R lnT to facilitate the analysis of isentropic processes of ideal gases with
variable specific heats. The function s+ also makes it possible to calculate the entropy changes of
ideal gases during processes when volume information is available instead of pressure information
and the variation of specific heats with temperature is to be accounted for. The introduction of the
function s
+
eliminates the need to use the dimensionless isentropic functions relative pressure Pr and
relative specific volume vr of ideal gases and to tabulate their values. The Pr and vr data are often
confused with pressure and specific volume, with an adverse effect on the study of the second law of
thermodynamics. The new s
+
function nicely complements the existing s
◦
function in entropy change
calculations: the former is conveniently used when volume information is given while the latter is
used when pressure information is available. Therefore, the introduction of the new entropy function
s
+
is expected to make a significant contribution to the thermodynamics education and research by
streamlining entropy analysis of ideal gases.
