Download - Vapor-Liquid Equilibriafor HFCs+ Propane
Vapor-Liquid Equilibria for HFCs + Propane
Hyun Sang Jin, Byung Gwon Lee, Dae Ryook Yang†, Jong Sung Lim*
CFC Alternative Research Center,
Environmental and Process Technology Division , KIST
Chemical Engineering, Korea University†
Chemical Engineering Sogang University*
*Corresponding author
Alternatives Research Center
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Introduction
Hydrofluorocarbons (HFCs) are a family of
refrigerants that have been specifically
developed to provide alternatives to CFCs and
HCFCs. They have many of the favorable
characteristics of CFCs especially those of zero
flammability and zero toxicity. However, HFCs are
powerful greenhouse gases that are identified in
the Kyoto Protocol.
Air conditioning has to use refrigerants and although there are Air conditioning has to use refrigerants and although there are Air conditioning has to use refrigerants and although there are Air conditioning has to use refrigerants and although there are many many many many
types of refrigerants, including air and water, types of refrigerants, including air and water, types of refrigerants, including air and water, types of refrigerants, including air and water, it is necessary to use it is necessary to use it is necessary to use it is necessary to use
chemicals for chemicals for chemicals for chemicals for reasonsofreasonsofreasonsofreasonsof efficiency and ultimately to conserve energy. efficiency and ultimately to conserve energy. efficiency and ultimately to conserve energy. efficiency and ultimately to conserve energy.
This can be done either by :This can be done either by :This can be done either by :This can be done either by :minimisingminimisingminimisingminimisingminimisingminimisingminimisingminimising leakage of HFC refrigerants to the lowest practical levelleakage of HFC refrigerants to the lowest practical levelleakage of HFC refrigerants to the lowest practical levelleakage of HFC refrigerants to the lowest practical levelleakage of HFC refrigerants to the lowest practical levelleakage of HFC refrigerants to the lowest practical levelleakage of HFC refrigerants to the lowest practical levelleakage of HFC refrigerants to the lowest practical level
or by using low Global Warming Potential refrigerants such as aor by using low Global Warming Potential refrigerants such as aor by using low Global Warming Potential refrigerants such as aor by using low Global Warming Potential refrigerants such as aor by using low Global Warming Potential refrigerants such as aor by using low Global Warming Potential refrigerants such as aor by using low Global Warming Potential refrigerants such as aor by using low Global Warming Potential refrigerants such as ammoniammoniammoniammoniammoniammoniammoniammonia
or or or or or or or or HCsHCsHCsHCsHCsHCsHCsHCs (hydrocarbons)(hydrocarbons)(hydrocarbons)(hydrocarbons)(hydrocarbons)(hydrocarbons)(hydrocarbons)(hydrocarbons)
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R11R11R11R11R11R11R11R11(CCl3F) is a single chlorofluorocarbon or
CFC compound. It has a high chlorine
content and ozone depletion potential (ODP)
and high global warming potential (GWP).
ODP = 1, GWP = 4000
R22R22R22R22R22R22R22R22(CHClF2) is a single hydrochloro-
fluorocarbon or HCFC compound. It has low
chlorine content and ozone depletion potential
and only a modest global warming potential.
ODP = 0.05, GWP = 1700
R236ea (R236ea (R236ea (R236ea (R236ea (R236ea (R236ea (R236ea (CHF2CHFCF3) is a
single hydrofluorocarbon or
HFC com-pound. Currently,
one of the leading candidates
to replace CFC-114 is R236ea.
ODP = 0, GWP = 1200
R290R290R290R290R290R290R290R290(CH3CH2CH) - Pure propane, a hydrocarbon (HC) an efficient
naturally occurring refrigerant with similar properties to R22.
ODP = 0, GWP = 3
R134aR134aR134aR134aR134aR134aR134aR134a(CH2FCF3) is a single hydro-
fluorocarbon or HFC com-pound. It
has no chlorine content, no ozone
depletion potential, and only a
modest global warming potential.
ODP = 0, GWP = 1300
Side by side comparison of
sea ice from 1979 and 2003
Courtesy NASA
Introduction
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Vapor liquid equilibrium data are required as one of the most imVapor liquid equilibrium data are required as one of the most imVapor liquid equilibrium data are required as one of the most imVapor liquid equilibrium data are required as one of the most important portant portant portant
types of information in types of information in types of information in types of information in evaluating the performance of refrigeration evaluating the performance of refrigeration evaluating the performance of refrigeration evaluating the performance of refrigeration
cyclescyclescyclescycles and and and and determining their optimal compositionsdetermining their optimal compositionsdetermining their optimal compositionsdetermining their optimal compositions....
In the present study, a blend of In the present study, a blend of In the present study, a blend of In the present study, a blend of propanepropanepropanepropane and nonflammable and nonflammable and nonflammable and nonflammable HFCsHFCsHFCsHFCs
refrirefrirefrirefrigerant are reduced both in global warming impact and flammagerant are reduced both in global warming impact and flammagerant are reduced both in global warming impact and flammagerant are reduced both in global warming impact and flammability.bility.bility.bility.
In this work, we measured VLE data for the binary mixture of In this work, we measured VLE data for the binary mixture of In this work, we measured VLE data for the binary mixture of In this work, we measured VLE data for the binary mixture of
HydrofluorocarboHydrofluorocarboHydrofluorocarboHydrofluorocarbonsnsnsns ((((HFCsHFCsHFCsHFCs) + propane) + propane) + propane) + propane at 273.15, 283.15, 293.15, at 273.15, 283.15, 293.15, at 273.15, 283.15, 293.15, at 273.15, 283.15, 293.15,
303.15, 313.15 and 323.15 K.303.15, 313.15 and 323.15 K.303.15, 313.15 and 323.15 K.303.15, 313.15 and 323.15 K.
Experimental data were cExperimental data were cExperimental data were cExperimental data were correlated with the orrelated with the orrelated with the orrelated with the PengPengPengPeng----Robinson and Robinson and Robinson and Robinson and PengPengPengPeng----
RobinsonRobinsonRobinsonRobinson----StryjekStryjekStryjekStryjek––––Vera equation of state using the WongVera equation of state using the WongVera equation of state using the WongVera equation of state using the Wong----Sandler and Sandler and Sandler and Sandler and
HuronHuronHuronHuron----Vidal mixing rules.Vidal mixing rules.Vidal mixing rules.Vidal mixing rules.
Purpose of research
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It was found that the CSD-EoS has been demonstrated to represent the
P-V-T properties. This equation of state is expressed as follows
( ) ( ))bVRT
a
y
yyy
RT
PV
+−
−
−++=
3
32
1
1
V
by
4= V : molar volume
In case of pure component, the temperature dependence of
‘a’ and ‘b’ are represented by the following forms:
( )2210 TTexpa ααα += 2
210 TTb βββ ++=
210ααα ,,
210βββ ,,The coefficient of in equation (3) and
in equation (4) were cited from REFPROP 5.0
CSD EoS
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∑∑== =
n
i
n
jijjim axxa
1 1
∑∑== =
n
i
n
jijjim bxxb
1 1
When i = j, the value of aii and bii are those of ‘a’ and ‘b’ of the pure
Components which are determined by equation (3) and (4). The values of
a12 and b12 can be expressed as following forms
( )( ) 21
22111212 1/
aafa −= ( )331
22
31
11128
1 // bbb +=
The model involves the adjustable binary parameters, f12, which
must be determined from experimental data.
In the application of CSD-EoS to mixture, there exists the effective
molecular parameters am and bm defined by using the following mixing
rules:
CSD EoS
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The VLE data were correlated with the Peng-Robinson equation of
state, which is expressed as follows
( ) ( )TP
TR.Ta
c
c α
=22
4572350
c
c
P
RT.b 0777960=
( )b)b(Vb)(VV
Ta
bV
RTP
MMMM −++−
−=
( ) ( )[ ] 2
/11 cTTkT −+=α
2ω26992.0ω54226.137464.0 −+=k
PR EoS
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Mixing rule
The Wong-Sander mixing rule was used in this work to obtain equation of state
parameters for a mixture from those of the pure components. This mixing rule
for a cubic equation of state can be written
( ) ( ) ( )[ ]( )ijjiij kRT/abRT/abRT/ab −−+−=− 1
2
1
C
A
b
ax
b
a E
ii
ii
m
m ∞+∑=
where C is a constant equal to in for the PR-EOS used in this work, kij is
binary interaction parameter
( )
∑−−∑∑ −
=∞
iiii
E
i jijji
m
RTb/axCRT/A
RT/abxx
b
1
W-S mixing rule
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is an excess Helmholtz free energy model at infinite pressure which
can be equated to a low-pressure excess Gibbs free energy
∑∑
∑τ
=∞
r
rir
j
jijij
i
i
E
Gx
Gx
xRT
A
( ) )/(exp RTAandG jijijijiji =−= ττα
where Gji is the local composition factor for the NRTL model, τji
is the NRTL model binary interaction parameter, Aji= (gji-gii),
where gji is an interaction energy parameter of the i-j component,
αji is a nonrandomness parameter and equal to 0.3 for the binary
mixture Investigated here
NRTL model
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Experimental procedure
A certain amount of HFCs was introduced into the cell.
After the desired temperature was achieved, the pressure of
the pure component was measured.
A proper amount of propane was supplied to the cell from a charging cylinder.
When the equilibrium was attained, pressure was measured.
The composition of the samples were measured by immediately
injecting them into the gas chromatograph.
H
F
C
s
+
p
r
o
p
a
n
e
x1, y
1
0.0 0.2 0.4 0.6 0.8 1.0
P(M
Pa)
0.0
0.5
1.0
1.5
2.0
2.5
HFCHFCHFCHFC----143a + Propane143a + Propane143a + Propane143a + Propane
Calc. with CSDCalc. with CSDCalc. with CSDCalc. with CSD----EoSEoSEoSEoS ((((------------))))
HFCHFCHFCHFC----227ea + Propane227ea + Propane227ea + Propane227ea + Propane
Calc. with RPCalc. with RPCalc. with RPCalc. with RP----EoSEoSEoSEoS using Wusing Wusing Wusing W----S mixing(S mixing(S mixing(S mixing(------------))))
P-x-y diagram for the HFC-143a + Propane
system Experimental data at 273.15(□);
283.15(■); 293.15(△); 303.15(▲); 313.15
(○); 323.15K(●).
Result and Discussion
<VLE curve>
x1, y1
0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
P(M
Pa)
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
1.1
1.2
1.3
P-x-y diagram for the HFC-227ea +
Propane system. Experimental data at
293.15(○); 303.15K(□).
HFCHFCHFCHFC----143a + Propane143a + Propane143a + Propane143a + Propane HFCHFCHFCHFC----227ea + Propane227ea + Propane227ea + Propane227ea + Propane
Result and Discussion
<The azeotropic composition with pressure>
P(MPa)
0.1 1 10
Azeotropic composition (mole fraction)
0.58
0.59
0.60
0.61
0.62
0.63
0.64
0.65
293.15K
303.15K
283.15K
273.15K
313.15K
323.15K
P(MPa)
0.1 1 10
Azeotropic composition (mole fraction)
0.79
293.15K
303.15K
H
F
C
s
+
p
r
o
p
a
n
e
Result and Discussion
HFC-227ea + propaneHFC-143a + propane
0.6376
0.6293
0.6239
0.6100
0.5997
0.5910
xx11
2.3139
1.8426
1.4551
1.1320
0.8594
0.6397
P(MPaP(MPa))
··323.15
··313.15
1.15110.7862303.15
0.89380.7925293.15
··283.15
··273.15
P(MPaP(MPa))xx11
TT
<The azeotropic data>
H
F
C
s
+
p
r
o
p
a
n
e
Result and Discussion
<Deviation of ΔΔΔΔP and ΔΔΔΔy>
x1 (HFC-143a mole fraction)
0.0 0.2 0.4 0.6 0.8 1.0
∆P
-0.10
-0.05
0.00
0.05
0.10
x1 (HFC-143a mole fraction)
0.0 0.2 0.4 0.6 0.8 1.0-0.10
-0.05
0.00
0.05
0.10
∆y
HFCHFCHFCHFC----143a + Propane143a + Propane143a + Propane143a + Propane
273.15(□); 283.15(■); 293.15(△); 303.15(▲); 313.15 (○); 323.15K(●).
H
F
C
s
+
p
r
o
p
a
n
e
Result and Discussion
<Deviation of ΔΔΔΔP/P(%) and ΔΔΔΔy>
HFCHFCHFCHFC----227ea + Propane227ea + Propane227ea + Propane227ea + Propane
x1(propane mole fraction)
0.0 0.2 0.4 0.6 0.8 1.0
∆P/P(%
)
-10
-8
-6
-4
-2
0
2
4
6
8
10
20C
30C
x1(propane mole fraction)
0.0 0.2 0.4 0.6 0.8 1.0
∆y1
-0.10
-0.08
-0.06
-0.04
-0.02
0.00
0.02
0.04
0.06
0.08
0.10
20C
30C
H
F
C
s
+
p
r
o
p
a
n
e
conclusion
The VLE of HFC-143a and HFC-227ea with propane system were used the PR EoS combined Wong-Sandler mixing rule and NRTL excess Helmholtz free energy model and CSD EoS
This mixing rule combined with PR equation of state and an activity coefficient model (NRTL) for the Aex term show very good correlation
The vapor-liquid equilibrium between measured and calculated values (AAD-P(%)) for HFCs + propane from 273.15K to 323.15K and the deviations were less than 0.61%
In this temperature, azeotropic behavior has been found in HFCs + propane systems.
H
F
C
s
+
p
r
o
p
a
n
e