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Fluid Phase Equilibria 297 (2010) 67–71

Contents lists available at ScienceDirect

Fluid Phase Equilibria

journa l homepage: www.e lsev ier .com/ locate / f lu id

sothermal vapor–liquid equilibrium data for the binary mixture ethyl fluorideHFC-161) + 1,1,1,2,3,3,3-heptafluoroproane (HFC-227ea) over a temperatureange from 253.15 K to 313.15 K

in Wang, Ying-Jie Xu, Zan-Jun Gao, Yu Qiu, Xu-Wei Min, Xiao-Hong Han ∗, Guang-Ming Chennstitute of Refrigeration and Cryogenics, State Key Laboratory of Clean Energy Utilization, Zhejiang University, Hangzhou 310027, China

r t i c l e i n f o

rticle history:eceived 7 April 2010eceived in revised form 6 June 2010ccepted 9 June 2010

a b s t r a c t

Vapor–liquid equilibrium (VLE) data for the refrigerant mixture ethyl fluoride (HFC-161) + 1,1,1,2,3,3,3-heptafluoroproane (HFC-227ea) are reported in the temperature range from 253.15 K to 313.15 K with asingle-phase circulation vapor–liquid equilibrium still. The results of the correlation for the vapor–liquidequilibrium data with Peng–Robinson (PR) equation of state (EOS), combined with the first Modified

vailable online 17 June 2010

eywords:FC-227eaFC-161apor–liquid equilibrium

Huron-Vidal (MHV1) mixing rule and Wilson model, are presented. These results are in a good agreementwith experimental data. The average and maximum derivations of vapor molar composition are within0.0130 and 0.0295 respectively, and the average and maximum relative derivations of pressure are within1.04% and 2.96%, respectively. The model parameters, determined from these binary data, are givento predict the phase behavior for a later ternary system. The binary system HFC-161 + HFC-227ea is a

nd ex

ixing rulequation of state

non-azeotropic mixture a

. Introduction

In the last years, the interest in using alternative hydro-fluoricefrigerants increased very much due to the negative influence onhe atmospheric ozone layer of the traditional ones. Ethyl fluo-ide (HFC-161) has excellent environmental characteristics amonghe fluorinated hydrocarbons of methane and ethane, such asero ozone depletion potential (ODP), a global warming potentialGWP) of 12, and a lifespan of 3 years in atmosphere. The mix-ure refrigerant HFC-161 + HFC-227ea is environmentally friendly,nd is considered as a promising alternative refrigerant of HCFCsor its excellent thermodynamic characteristics [1]. However, asn important compound of refrigerant mixture, the vapor–liquidquilibrium (VLE) data which are very important in building uphe models for application in refrigerating machines, are hardlyound in the published literature. Therefore, in this paper, VLE dataor the refrigerant mixture HFC-161 + HFC-227ea over a temper-ture range from (253.15 to 313.15) K are reported. In order toredict the behavior of this mixture HFC-161 + HFC-227ea, the nec-ssary parameters for one thermodynamic model are also reported.

t is essential to develop accurate thermodynamic models for thengineering design and optimization of the binary mixture HFC-61 + HFC-227ea.

∗ Corresponding author. Tel.: +86 571 87951738; fax: +86 571 87952464.E-mail address: hanxh66@zju.edu.cn (X.-H. Han).

378-3812/$ – see front matter © 2010 Elsevier B.V. All rights reserved.oi:10.1016/j.fluid.2010.06.006

hibits a negative deviation from Raoult’s law.© 2010 Elsevier B.V. All rights reserved.

2. Experiments

2.1. Materials

HFC-161 and HFC-227ea samples are supplied by Zhejiang Lan-tian Environment Protection Hi-Tech Co., Ltd, with a minimummass fraction purity of 99.74% and 99.98%, respectively. No furtherpurification was done on these chemicals before use.

2.2. Experimental equipment

Pressure–temperature–liquid and vapor composition (P–T–x–y)data were obtained from experiments made with a recirculatingstill. The schematic experimental setup in this work is shown in theliterature it consists of a 80 mL stainless steel equilibrium cell withtemperature and pressure measuring systems [2,3] The equilibriumcell is mounted in a 18 L glass thermostatic bath insulated withpolyurethane foams. In the operating range of 253.15–313.15 K, thebath temperature stability has been estimated within ±0.01 K. Thetemperature is measured by a four-head 25-platinum resistancethermometer (Model: WZPB-2, China) with an uncertainty within±10 mK and a Keithley 2010 data acquisition/switch unit. The

overall temperature uncertainty of the temperature measurementsystem was ±15 mK. The pressure measurement system includesa pressure transducer (Model: PMP4010, Drunk), a differentialpressure null transducer (Model: 1151DP, China), an oil-pistontype dead-weight pressure gauge (Model: YS-6·60·250·600, China),

6 se Equilibria 297 (2010) 67–71

apttiwb

wIb

Table 1Critical parameters and acentric factors [7,8].

Substance Chemicals Molecular weight Tc/K Pc/MPa ω

TV

8 Q. Wang et al. / Fluid Pha

nd an atmospheric pressure gauge (Model: DYM-1, China). Theressure inside the cell is transferred to a differential pressureransmitter and balanced with nitrogen. The total uncertainty ofhe pressure measurement system is ±1.6 kPa. The phase behav-or can be seen clearly from the double glass window on the

all of the equilibrium cell and the glass wall of the thermostatic

ath.

The equilibrium compositions of the vapor and liquid phaseere determined using gas chromatograph equipped with a Flame

onization Detector (FID) (Model: GC112A, China). The GC was cali-rated with pure components of known purity and with mixtures of

able 2LE results for the binary mixture of HFC-161(1) + HFC-227ea(2) in the temperature rang

T (K) x1 y1,exp pexp (kPa) yexp − yca

253.15 0.7222 0.9036 166.08 0.01070.8413 0.9487 192.60 −0.0070

263.15 0.0814 0.0858 132.85 −0.01070.1785 0.2150 137.65 −0.02950.2478 0.3333 145.61 −0.02460.3376 0.4923 160.45 −0.00610.4446 0.6338 180.39 −0.00930.5207 0.7239 199.10 −0.00300.5987 0.7907 216.21 −0.00760.7599 0.8938 256.19 −0.01210.8501 0.9334 271.22 −0.0148

273.15 0.1223 0.1472 199.68 −0.01310.1601 0.1975 207.49 −0.01690.1974 0.2505 208.33 −0.01850.2574 0.3411 216.89 −0.01620.3002 0.4195 228.00 0.00000.4246 0.5752 252.45 −0.01380.4834 0.6456 268.05 −0.01450.6339 0.7831 314.39 −0.02580.7805 0.8905 361.40 −0.02010.8614 0.9320 392.70 −0.0196

283.15 0.0445 0.0487 278.89 −0.00360.1497 0.1824 290.56 −0.01800.2418 0.3252 308.45 −0.01640.3190 0.4432 329.33 −0.01260.4263 0.5836 363.80 −0.01330.5055 0.6704 404.15 −0.01480.5878 0.7514 435.20 −0.01170.7049 0.8369 478.55 −0.01640.8624 0.9362 537.43 −0.0065

293.15 0.0984 0.1163 396.86 −0.01110.1415 0.1682 406.92 −0.01770.2677 0.3376 431.65 −0.02200.3413 0.4430 458.75 −0.01530.4462 0.5787 503.23 −0.01070.5247 0.6672 546.60 −0.01020.6008 0.7532 573.50 −0.00020.7238 0.8469 647.70 −0.00880.8761 0.9370 724.31 −0.01140.0815 0.0979 535.46 −0.0087

303.15 0.1200 0.1592 544.82 0.00200.2341 0.3211 576.89 0.01450.3049 0.4122 612.42 0.01430.4515 0.5937 667.43 0.01650.5338 0.682 714.53 0.01260.6109 0.7424 781.20 −0.00540.7122 0.8223 842.10 −0.01590.8640 0.9237 944.74 −0.0165

313.15 0.0867 0.1213 708.09 0.01430.1197 0.1582 718.00 0.00940.2385 0.3137 751.35 0.01140.2881 0.3815 776.67 0.01480.4056 0.5451 852.80 0.02730.4611 0.6103 888.45 0.02350.5462 0.6931 975.59 0.00690.6489 0.7860 1045.53 −0.00850.7618 0.8737 1196.05 −0.0158

HFC-161 CH3-CH2F 48.06 375.30 5.02 0.2155HFC-227ea CH3CHFCF3 170.03 374.8 2.926 0.3570

known composition that were prepared gravimetrically. The exper-imental data at the equilibrium state were measured at least threetimes in order to ensure repeatability. Considering the margin oferror and reproducibility of GC, an overall uncertainty of the com-

e from (253.15 to 303.15) K.

l100(pexp−pcal)

pexp�1 �2 ln �1

�2

0.29 0.978 0.713 0.13740.08 1.032 0.587 0.2449

−0.73 0.531 0.991 −0.2714−1.35 0.640 0.965 −0.1782−0.72 0.709 0.938 −0.1216

0.61 0.786 0.899 −0.05830.91 0.860 0.849 0.00562.18 0.901 0.813 0.04471.82 0.935 0.776 0.08062.07 0.979 0.704 0.1432

−0.69 0.992 0.666 0.1730

−1.53 0.637 0.991 −0.19220.46 0.662 0.984 −0.1721

−1.15 0.687 0.976 −0.1524−0.93 0.727 0.961 −0.1212

0.97 0.754 0.947 −0.09910.68 0.827 0.898 −0.03581.10 0.859 0.871 −0.00611.80 0.927 0.791 0.06880.94 0.973 0.703 0.14121.56 0.989 0.652 0.1810

−0.79 0.582 0.998 −0.2346−0.62 0.690 0.980 −0.1527−0.53 0.771 0.954 −0.0926−0.22 0.827 0.929 −0.0502−0.06 0.889 0.890 −0.0005

2.86 0.923 0.861 0.03032.44 0.951 0.831 0.05821.32 0.977 0.791 0.0920

−0.38 0.996 0.740 0.1290

−1.19 0.689 0.996 −0.1600−0.42 0.711 0.992 −0.1442−1.30 0.776 0.970 −0.0969−0.07 0.812 0.951 −0.0686

1.19 0.860 0.916 −0.02712.82 0.893 0.884 0.00470.96 0.922 0.848 0.03642.00 0.961 0.782 0.0892

−0.34 0.992 0.689 0.1582−1.86 0.727 0.999 −0.1377

−1.72 0.740 0.997 −0.1295−1.50 0.778 0.986 −0.1026

0.66 0.803 0.974 −0.0836−0.23 0.858 0.935 −0.0373

0.44 0.890 0.903 −0.00622.96 0.919 0.864 0.02691.65 0.956 0.801 0.0766

−0.56 0.995 0.691 0.1581

−1.88 0.710 0.998 −0.1476−1.58 0.723 0.996 −0.1389−2.04 0.773 0.981 −0.1035−1.34 0.796 0.971 −0.0866

0.71 0.853 0.936 −0.04010.75 0.882 0.912 −0.01422.81 0.929 0.865 0.0313

−0.21 0.988 0.789 0.09780.42 1.051 0.680 0.1890

se Equ

pf

2

((

(

(

(

3

Rer

p

a

˛

b

wtcb

t

b

wpi

TT

Q. Wang et al. / Fluid Pha

osition measurement was estimated to ±0.002 in mole fractionor both the liquid and vapor phases.

.3. Experimental procedures

1) The equilibrium cell was evacuated to remove inert gases;2) A targeted amount of HFC-161 and HFC-227ea was added into

the equilibrium cell;3) The temperature of the equilibrium cell and thermostated

bath was maintained by the temperature controlling system,meanwhile, the vapor in the equilibrium cell was circulatedcontinuously by the magnetic circulation pump. 2 h or morewas sufficient to establish a thermal equilibrium state betweenthe cell and thermostated bath;

4) After the desired equilibrium temperature was attained, thepressure in the equilibrium cell was measured;

5) Then vapor and liquid samples were withdrawn from therecycling lines by the vapor–liquid sampling valves and weremeasured in the GC, respectively.

. Model

The correlation of the VLE data for the binary mixture HFC-161 + HFC-R227ea was made by means of the Peng–Robinson (PR)quation of state (EOS) with Modified Huron-Vidal (MHV1) mixingule.

Peng–Robinson equation of state [4] is

= RT

v − b− a

v2 + 2vb − b2(1)

= 0.45724˛(T)R2T2c /pc (2)

(T) = (1 + (0.37464 + 1.54226ω − 0.26992ω2)(1 − T0.5r ))

2(3)

= 0.07780RTc/pc (4)

here p is the pressure, Pa, v is the molar volume, m3 mol−1, T ishe absolute temperature, K, pc is the critical pressure, Pa, Tc is theritical temperature, K, R is general gas constant, J mol−1 K−1, a andare equation of state dependent parameters, ω is acentric factor.

In equation of state approach, the mixing rule used to correlatehe vapor–liquid equilibrium is the MHV1 mixing rule [5]

am

bmRT= 1

CMHV1

GE

RT+ 1

CMHV1

∑i

xi ln(

bm

bi

)+

∑i

xiai

biRT(5)

m =∑

xibi (6)

i

here GE is the excess Gibbs energy, subscripts m and i denote thearameters of the mixture and ith component, respectively, CMHV1

s determined by the equation of state, x is the liquid mole fraction.

able 3he results of correlation for vapor–liquid equilibrium data at different temperatures usin

T (K) Np PR + MHV1

�y ıp (%) m

253.15 2 0.0107 0.19 0263.15 9 0.0131 1.23 0273.15 10 0.0159 1.11 0283.15 9 0.0126 1.02 0293.15 9 0.0119 1.14 0303.15 9 0.0118 1.29 0313.15 9 0.0147 1.31 0

ilibria 297 (2010) 67–71 69

The excess Gibbs energy GE is calculated using the Wilson model[6]

GE

RT= −x1 ln(x1 + �12x2) − x2 ln(�21x1 + x2) (7)

where �12, �21 are adjustable parameters.Activity coefficients obtained by Wilson model are

ln �1 = −ln(x1 + �12x2) + ˇx2 (8)

ln �2 = −ln(�21x1 + x2) − ˇx1 (9)

where

ˇ = �12

x1 + �12x2− �21

�21x1 + x2.

For the corresponding correlations of the binary data by meansof PR + MHV1 model were generated by minimizing the followingobjective function

OF = 1Np

Np∑j

((pexp − pcal

pexp

)2

j

+ (y1,exp − y1,cal)2j + (y2,exp − y2,cal)

2j

)(10)

where the subscript exp and cal denote the calculated and experi-mental data, respectively, Np is the number of experimental points,j denotes the jth experimental point.

VLE data calculation was performed with the application of thefollowing equilibrium condition

yiϕvi p = xiyip

sati ϕsat

i (11)

where y is the mole fraction in the vapor phase, ϕ is the fugacitycoefficient, � is the activity coefficient, the superscript sat denotesthe parameter of the saturated property of the pure refrigerants,respectively.

The critical temperature Tc, critical pressure pc, and acentricfactor ω of each pure component are listed in Table 1.

4. Results and discussion

The isothermal VLE experimental results for the binary systemHFC-161 + HFC-227ea in the temperature range from 253.15 K to313.15 K are given in Table 2 and Fig. 1.

The VLE data were correlated with PR EOS with MHV1 mixingrule while the Wilson activity coefficient model was used to cal-culate the excess Gibbs free energy. The saturated pressures forHFC-161, HFC-227ea were taken from Refs. [7,8]. For the correlationof the experimental data, a computer program has been developed.Here, the least squares method was applied for fitting the above-

mentioned objective function. The results of the correlation for thebinary mixture are listed in Table 2 and the optimum values of thebinary interaction parameters �12, �21 are given in Table 3.

The correlated results are shown in Table 2 and Fig. 1. The devi-ations of vapor phase composition and vapor pressure are shown

g PR + MHV1/Wilson model.

Interaction parameters

ax �y max ıp (%) �12 �21

.0022 0.29 4.2950 −0.0044

.0295 2.18 0.7229 2.1677

.0258 1.56 1.2695 1.3559

.0164 2.86 0.2365 3.0690

.0220 2.82 1.3807 1.1280

.0165 2.96 3.3891 0.1331

.0273 2.81 4.1721 −0.0403

70 Q. Wang et al. / Fluid Phase Equ

Fig. 1. Isothermal VLE for the binary mixture HFC-161(1) + HFC-227ea(2) at thetemperature range of (253.15–303.15) K.

Fig. 2. Deviations of vapor phase molar composition for the binary mixture HFC-161(1) + HFC-227ea(2).

Fig. 3. Deviations of vapor pressure for the binary mixture HFC-161(1) + HFC-227ea(2).

ilibria 297 (2010) 67–71

in Table 3 and Figs. 2 and 3. The ıp and �y in Table 3 are defined asfollows

ıp = 1/Np∑

i

∣∣(pcal − pexp)/pexp∣∣i× 100 (12)

�y = 1/Np∑

i

∣∣ycal − yexp∣∣i

(13)

From the results in Table 2 and Fig. 1, we can see that binarysystem HFC-161 + HFC-227ea is the zeotropic mixture. In addition,it can been seen that �1, �2 are less than 1, which indicates thatthe binary system HFC-161 + HFC-227ea exhibits a negative devi-ation from Raoult’s law. From the results in Tables 2 and 3 andFigs. 2 and 3, we can see that within a wide range of tempera-tures and pressures, the PR + MHV1 coupled with Wilson modelreproduces reasonably well the experimental data. The averageand maximum derivations of vapor molar composition are within0.0130 and 0.0295 respectively, and the average and maximumrelative derivations of pressure are within 1.04% and 2.96%.

5. Conclusions

In this paper, isothermal vapor–liquid equilibrium of the refrig-erant mixture HFC-161 + HFC-227ea were investigated in thetemperature range from (253.15–313.15) K. Using PR equation ofstate, combined with the MHV1 mixing rule and Wilson model,the vapor–liquid equilibrium data are correlated. The interactionparameters of the Wilson model were given. It is shown that thereis a good agreement between the calculated and experimental data.No azeotrope was found in the binary system, and the systemexhibits negative deviations from ideality.

List of symbolsa parameter of the equation of state (J m3 mol−2)b parameter of the equation of state (m3 mol−1)CMHV1 constant in Eq. (5)GE excess Gibbs free energy (J mol−1)Np number of experimental pointsOF objective functionP equilibrium pressure (MPa)R gas constant (J mol−1 K−1)T equilibrium temperature (K)v molar volume (m3 mol−1)x liquid mole fractiony vapor mole fractionZ compressibility factor

Greek letters˛(T) temperature functionˇ parameter of Wilson model� adjustable parameter of Wilson modelω acentric factorϕ fugacity coefficient� activity coefficientıp deviation of p�y deviation of y

Superscriptssat saturation property

Subscriptsc critical propertycal calculated propertyexp experimental propertym mixture

se Equ

ij12

A

FuEp

[[[

[4] D.Y. Peng, D.B. Robinson, Ind. Eng. Chem. Fundam. 15 (1976) 59–64.[5] M.L. Michelsen, Fluid Phase Equilib. 60 (1990) 213–219.[6] G.M. Wilson, J. Am. Chem. Soc. 86 (1964) 127–130.

Q. Wang et al. / Fluid Pha

ith pure refrigerantjth experimental pointcomponent 1component 2

cknowledgements

This work has been supported by the Nation Natural Scienceoundation of China (No. 50806063) and Zhejiang Provincial Nat-ral Science Foundation of China (Y1090455). The support of thexcellent Young Teachers Program of Zhejiang University (Zijinrogram) is gratefully acknowledged.

[

[

ilibria 297 (2010) 67–71 71

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