ME2121 – Engineering Thermodynamics

Entropy (Cont’d)
Absolute values of entropy are determined on the
basis of the third law of thermodynamics.
Engineers are usually concerned with the changes
in entropy.
The entropy of a substance can be assigned a zero
value at some arbitrarily selected reference state.
To perform the integration in Eq. 6-5 one needs to
know the relation between Q and T during a
process. For the majority of cases we have to rely
on tabulated data for entropy.
© Copyright 2005 Prof. Arun S. Mujumdar.
ME2121 - Entropy I - Introduction (ASM) 28