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Unformatted text preview: the substance over the given temperature interval. Note that the entropy change of a truly incompressible substance depends on temperature only and is independent of pressure.
Equation 7–28 can be used to determine the entropy changes of solids and
liquids with reasonable accuracy. However, for liquids that expand considerably with temperature, it may be necessary to consider the effects of volume
change in calculations. This is especially the case when the temperature
change is large.
A relation for isentropic processes of liquids and solids is obtained by setting the entropy change relation above equal to zero. It gives
Isentropic: s2 s1 Cav ln T2
T1 0 → T2 T1 (7–29) That is, the temperature of a truly incompressible substance remains constant
during an isentropic process. Therefore, the isentropic process of an incompressible substance is also isothermal. This behavior is closely approximated
by liquids and solids. cen54261_ch07.qxd 11/18/03 9:57 AM Page 294 294
FUNDAMENTALS OF THERMAL-FLUID SCIENCES EXAMPLE 7–7 Effect of Density of a Liquid on Entropy Liquid methane is co...
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