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

Technology DivisionTechnology DivisionTechnology DivisionTechnology DivisionNational Research Lab

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)


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


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


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


∑∑== =

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


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


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


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


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


<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


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


<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


<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

vapor-liquid equilibriafor hfcs+ propane

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