8/13/2019 Understanding Thermodynamics Properties Tables
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2. If the gi"en specific "olue is less than the specific "olue
of the saturated li&uid$ youare in the copressed li&uid
state# In this case$ you ay ha"e copressed li&uid ta(lesfor
high pressures or else you can estiate the properties as those of
the saturated li&uidat the given temperature# )If you are gi"en
the pressure$ you ha"e to find the saturationteperature to ake the
appro'iation for the copressed li&uid#*
3# If the gi"en specific "olue is greater than the specific
"olue of the saturated "apor$you are in the superheated "apor )gas*
state# +ere you use the gi"en teperature )orpressure* and specific
"olue in the gas ta(les# This usually re&uires an interpolation
tofind the gi"en specific "olue#
,# If the gi"en specific "olue is greater than the specific
"olue of the saturated li&uid andless than the specific "olue
of the saturated "apor$ you are in the i'ed region# +ereyou find
the &uality as )" > " f*)"g> "f*# @ou can then use this
&uality to find otherproperties$ such as the internal energy$
as u / u fA ')ug> uf*#
5# -'aple# %or !ater at 200 ka !ith a specific "olue of 0#5 3kg
!e find that thespecific "olues of the saturated li&uid and
saturated "apor at the gi"en pressure of 200ka are "f/ 0#00101
3kg and "g/ 0#4457 3kg# Thus !e are in the i'ed regionand !e
ha"e to copute the &uality as ' / )" B "f*)"gB "f* / )0#5 B
0#00101* )0#4457 B0#00101* / 0#5,# nce !e kno! the &uality !e
can find all other properties# %ore'aple the enthalpy is found as h
/ h fA ' hfg/ 50,#70 A )0#5,*)2201#* / 17,# k6kg#
# nother e'aple# %or !ater at 500o% !ith a specific "olue of
ft3l($ !e see that thisspecific "olue is greater than the specific
"olue of the saturated li&uid at 500o%$ !hichis 0#71 3kg so !e
kno! that !e are in the gas )superheat* region# Scanning theta(les
for T / 500o%$ !e find a specific "olue of 7#017 ft3l(at 40 psia
and a specific"olue of 5#547 ft3l(at 100 psia# Thus our gi"en
specific "olue of ft
3l(ust (e(et!een these pressures# .e ha"e to interpolate using
the follo!ing e&uation for ageneral property @ !hich ay
e&ual $ u$ s$ or h# %irst !e find the interpolation factor$
f$!hich is a easure of the relati"e distance (et!een the t!o data
points# 9ote that f !ill(e negati"e in this case (ecause " is
decreasing as is increasing#
mm
mm
lbft
lbft
lbft
lbft
f33
33
017.7587.5
017.76
=
.e then use this factor to copute any property that is ta(ulated
at the t!o pressures# In thee&uation (elo!$ @ represents u$ h$
s$ or #
( ))80,500()100,500()80,500(6,500 0003
0psiaFYpsiaFYfpsiaFY
lbft
FYm
+=
C. If you are given temperature !or pressure" and another
specific property !specificinternal energy, specific enthalpy, or
specific entropy", follow the same process usedas in part . #his is
written below using entropy as a specific e$ample, but you coulduse
energy or enthalpy.
1# se the gi"en pressure or the gi"en teperature to find the
specific entropy of thesaturated li&uid )sf* and saturated
"apor )sg*#
-ngineering ;uilding ail: lcaretto?csun#edu 43,4 %a':
414#77#702
mailto:[email protected]:[email protected]
8/13/2019 Understanding Thermodynamics Properties Tables
3/3
2# If the gi"en specific entropy is less than the specific
entropy of the saturated li&uid$ youare in the copressed
li&uid state# In this case$ you ay ha"e copressed li&uid
ta(lesfor high pressures or else you can estiate the properties as
those of the saturated li&uidat the given temperature# )If you
are gi"en the pressure$ you ha"e to find the saturationteperature
to ake the appro'iation for the copressed li&uid#*
3# If the gi"en specific entropy is greater than the specific
entropy of the saturated "apor$you are in the superheated "apor
)gas* state# +ere you use the gi"en teperature )orpressure* and
specific entropy in the gas ta(les# This usually re&uires an
interpolation tofind the gi"en specific entropy#
,# If the gi"en specific entropy is greater than the specific
entropy of the saturated li&uid andless than the specific
entropy of the saturated "apor$ you are in the i'ed region# +ereyou
find the &uality as )s > s f*)sg> sf*# @ou can then use
this &uality to find otherproperties$ such as the internal
energy$ as u / u fA ')ug> uf*#
5# The e'aples in this case proceed in e'actly the sae !ay as
the e'aples for case ;#nly the other specified property replaces
the specific "olue in the e'aples#
-ngineering ;uilding ail: lcaretto?csun#edu 43,4 %a':
414#77#702
mailto:[email protected]:[email protected]
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