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Enthalpy-Entropy (h-s) or Mollier Diagram | Up
Thermodynamics Heat Transfer and Fluid Flow Volume 1 of 3 | Next
Use of Mollier Chart |
PROPERTY DIAGRAMS AND STEAM TABLES
Thermodynamics
nfg
=
specific volume change of vaporization (ft3/lbm)
h
=
specific enthalpy (Btu/lbm)
hf
=
specific enthalpy of saturated liquid (Btu/lbm)
hg
=
specific enthalpy of saturated vapor (Btu/lbm)
hfg
=
specific enthalpy change of vaporization (Btu/lbm)
s
=
specific entropy (Btu/lbm-°R)
sf
=
specific entropy of saturated liquid (Btu/lbm-°R)
sg
=
specific entropy of saturated vapor (Btu/lbm-°R)
sfg
=
specific entropy change of vaporization (Btu/lbm-°R)
Sh
=
number of degrees of superheat (°F)
The saturated steam tables give the energy transfer properties of saturated water and saturated
steam for temperatures from 32 to 705.47°F (the critical temperature) and for the corresponding
pressure from 0.08849 to 3208.2 psi. Normally, the saturated steam tables are divided into two
parts: temperature tables, which list the properties according to saturation temperature (Tsat); and
pressure tables, which list them according to saturation pressure (Psat). Figure A-2 shows a
portion of a typical saturated steam temperature table and a portion of a typical saturated steam
pressure table. The values of enthalpy and entropy given in these tables are measured relative
to the properties of saturated liquid at 32°F. Hence, the enthalpy (hf) of saturated liquid and the
entropy (sf) of saturated liquid have values of approximately zero at 32°F.
Most practical applications using the saturated steam tables involve steam-water mixtures. The
key property of such mixtures is steam quality (x), defined as the mass of steam present per unit
mass of steam-water mixture, or steam moisture content (y), defined as the mass of water present
per unit mass of steam-water mixture. The following relationships exist between the quality of
a liquid-vapor mixture and the specific volumes, enthalpies, or entropies of both phases and of
the mixture itself. These relationships are used with the saturated steam tables.
HT-01
Page 48
Rev. 0
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