ENTROPY:ENTROPY CHANGE OF LIQUIDS AND SOLIDS

ENTROPY CHANGE OF LIQUIDS AND SOLIDS

Recall that liquids and solids can be approximated as incompressible sub- stances since their specific volumes remain nearly constant during a process. Thus, du � 0 for liquids and solids, and Eq. 7–25 for this case reduces to

ENTROPY-0196

where Cav is the average specific heat of the substance over the given temperature interval. Note that the entropy change of a truly incompressible sub- stance 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 consider- ably 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 set- ting the entropy change relation above equal to zero. It gives

ENTROPY-0197

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.

ENTROPY-0198ENTROPY-0199ENTROPY-0200

Related posts:

Benefits, drawbacks and operational issues:Tangible benefits to the user
Concepts for estimating pumping energy costs:Systems without static head or closed loop systems
Compressed Air Transmission and Treatment:Oil removal and Oil vapour
Compressed Air Transmission and Treatment:Check list for compressed air filters
Low pressure and vacuum:Discharge period and pulsations and Positive pressure systems.
VALVES:fLOW CONTROL VALVES
CHARACTERISTICS OF COMPRESSED AIR:THERMODYNAMICS
RESERVOIRS, STRAINERS, FILTERS, AND ACCUMULATORS:Diaphragm Accumulators.
Control components in a hydraulic system:Hydraulic fuses.
LINES, FITTINGS, AND SEALS:LINES, FITTINGS, AND SEALS
Hydraulic accumulators.
Air Compressors, Air Treatment and Pressure Regulation:screw compressors
Safety, Fault-Finding and Maintenance:cleanliness
BASICCONCEPTS OF THE RMODYNAMICS:TEMPERATURE AND THE ZEROTH LAW OF THERMODYNAMICS
ENERGY TRANSFER BY HEAT,WORK,AND MASS:NONMECHANICAL FORMS OF WORK

Leave a comment

Your email address will not be published. Required fields are marked *