17 Thermodymanic Properties of Refrigerant 500 A. P. KUDCHADKER
Downloaded by UNIV OF ARIZONA on December 6, 2012 | http://pubs.acs.org Publication Date: December 1, 1979 | doi: 10.1021/ba-1979-0182.ch017
1
Thermodynamics Research Center and Department of Chemical Engineering, Texas A&M University, College Station, TX 77843 and Department of Chemical Engineering, Indian Institute of Technology, Kanpur, U. P., India
For design calculations involving Refrigerant 500, a mini mum-boiling azeotrope of 39.4 mol % of 1,1-difluoroethane and 60.4 mol % of difluorodichloromethane, reliable real gas thermodynamic properties are required which have been calculated from 0.2 to 100 bar and from 220 to 540 Κ using the recently proposed Boublik-Adler-Chen-Kreglewski equation of state and the PVT data reported in the literature. This equation of state has 21 universal constants and only five adjustable constants which have been calculated for R-500 from the PVT data, saturated vapor pressure and liquid density, and the critical constants. In order to calcu late the absolute values of the real gas properties, the ref erence state properties, which are also reported here, are required. A l l properties are given in SI units.
ecent
applications
compression
of
m i n i m u m - b o i l i n g azeotropes
to t h e
vapor
r e f r i g e r a t i o n systems h a v e i n d i c a t e d t h e i r s u p e r i o r i t y
over t h e i r p u r e constituents u n d e r i d e n t i c a l c o n d i t i o n s
(1,2).
While
r e t a i n i n g t h e merits of p u r e c o m p o n e n t refrigerants, t h e use o f m i n i m u m b o i l i n g azeotropes has r e s u l t e d i n i n c r e a s e d c a p a c i t y , a t t a i n m e n t of l o w e r t e m p e r a t u r e s , a n d , c o n s e q u e n t l y , i m p r o v e d coefficients
of
performance.
R e f r i g e r a n t 5 0 0 ( R - 5 0 0 ) is a m i n i m u m - b o i l i n g azeotrope
o f 26 w t %
(39.4 m o l % ) of 1,1-difluoroethane ( R - 1 5 2 a ) a n d 74 w t % (61.6 m o l % ) of d i f l u o r o d i c h l o r o m e t h a n e ( R 1 2 ) . Present address: Department of Chemical Engineering, Indian Institute of Tech nology Bombay, Powai, Bombay 400 076, India. 1
0-8412-0500-0/79/33-182-305$05.00/l © 1979 American Chemical Society
In Equations of State in Engineering and Research; Chao, K., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
In Equations of State in Engineering and Research; Chao, K., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
3
^
=
^ ( 1
+
^ψ) *
nm
D
a r e un
v
» ersal constants,
C, a, u°/k. and τ?Μ are characteristic constants,
:
+
\7·
=
1
=
'
Ι η Ζ
ex
u
t a
P
9
(I - t)
4
2
2
Ι)Ί - Γ ί Γ / β ^ , λ
" (l - i ) J ~
2
(a -
( d 7 ^ \ * (ira") • riir'X j*F [*
2
Ι"4α + 6a + ( 2 a - 6a)t
A
T
= ( - j ( .
1
W 1 bar; h o w e v e r , not b e l o w T/T = 0 . 5 5 .
c
the relative errors are about five times larger than i n other regions. T h e equations are valid for argon at least u p to the reduced temperature T/T - 7 and pressure P/P = 2 0 and similar ranges o f
A t l/V » 0 a l l the residual functions are equal t o zero and Ζ = φ = 1. I n the f o l l o w i n g tables, the values b e l o w the c r i t i c a l temperature are given for the l i q u i d a n d the vapor phase. F o r the l i q u i d ,
Notes:
(9P\
fiP\
Downloaded by UNIV OF ARIZONA on December 6, 2012 | http://pubs.acs.org Publication Date: December 1, 1979 | doi: 10.1021/ba-1979-0182.ch017
ϋ
CO Ο *4
Ox Ο Ο
3
OS
M
308
EQUATIONS
The
B o u b l i k - A l d e r - C h e n - K r e g l e w s k i (henceforth
BACK)
OF
referred
STATE
t o as
e q u a t i o n so f a r h a s b e e n successfully a p p l i e d t o c a l c u l a t e t h e
r e s i d u a l properties of s u l f u r d i o x i d e , h y d r o g e n sulfide, b e n z e n e ,
naph
thalene, t e t r a l i n , cis- a n d f r a n s - d e c a l i n , f u r a n , a n d t e t r a h y d r o f u r a n
(3,4).
I n the present i n v e s t i g a t i o n , t h e c o m p r e s s i o n factor, f u g a c i t y coeffi c i e n t , a n d r e s i d u a l t h e r m o d y n a m i c f u n c t i o n s of t h e r e a l fluid R - 5 0 0 h a v e b e e n c a l c u l a t e d u s i n g t h e B A C K e q u a t i o n o f state. F o r this p u r p o s e , t h e e x p e r i m e n t a l d a t a , i.e., c r i t i c a l constants, saturated l i q u i d d e n s i t y , s a t u r a t i o n v a p o r pressure, a n d t h e PVT d a t a h a v e b e e n u t i l i z e d . T h e PVT d a t a f o r R - 5 0 0 as r e p o r t e d b y S i n k a a n d M u r p h y ( 5 ) extends f r o m 322 t o 478 K , 14 t o 58 b a r , a n d 17 to 149 m k m o l " , a n d Downloaded by UNIV OF ARIZONA on December 6, 2012 | http://pubs.acs.org Publication Date: December 1, 1979 | doi: 10.1021/ba-1979-0182.ch017
3
1
f r o m 298.15 to 413.15 K , 0.2 to 7 b a r , a n d 3 t o 80 m k m o l " as stated b y 3
1
P r a s a d a n d K u d c h a d k e r (6). A S H R A E ( 7 ) has r e p o r t e d t h e s a t u r a t e d a n d s u p e r h e a t e d p r o p e r t i e s of R - 5 0 0 f r o m 188 to 530 Κ a n d f r o m 0.04 t o 55 b a r . T h e s e values a r e b a s e d u p o n t h e measurements o f S i n k a a n d M u r p h y ( 5 ) . F o r t h e present c a l c u l a t i o n s a l l temperatures w e r e c o n v e r t e d t o IPTS-68 a n d a l l d e r i v e d properties a r e r e p o r t e d i n S I u n i t s . Basic
Data C r i t i c a l constants ( 5 ) : T = 378.65 K ; P = 44.26 b a r ; V — 0.200 c
c
m
3
kmol" ; 1
c
— 497 k g m " . 3
P c
S a t u r a t e d l i q u i d d e n s i t y ( 5 ) : t h e d a t a w e r e fitted t o t h e m o d i f i e d G u g g e n h e i m e q u a t i o n as p r o p o s e d b y H a y n e s a n d H i z a ( δ ) .
(ρ - p ) /m kmol" — 932.468 (1 - Τ ) · 3
c
1
Γ
— 2421.08 (1 - T ) r
0
35
+ 1481.05 (1 - T ) r
+ 1442.92 (1 - Γ )
4/3
Γ
5 / 3
S a t u r a t i o n v a p o r pressure ( 5 ) : t h e d a t a w e r e fitted t o t h e W a g n e r e q u a t i o n (9).
lnP
r
-7.04046[(1 -
T )/T ]
= -2.86953[(1 -
T ) /T ]
T
T
+ 1.47146[(1 -
T
3
+ 13.7355[(1 -
r
T V' T ] 5/
r
r
T ) /T ] r
7
r
—38.2370[ (1 - r ) / r ] r
where T
=T/T .
Derived
Properties
t
9
r
C
T h e B A C K e q u a t i o n o f state u s e d i n this w o r k contains 24 u n i v e r s a l constants a n d five c h a r a c t e r i s t i c constants as r e p o r t e d i n T a b l e I . T h e e q u a t i o n w i t h 24 u n i v e r s a l constants fitted t h e e x p e r i m e n t a l d a t a o n R - 5 0 0 m u c h better t h a n t h e e q u a t i o n w i t h 20 constants f o r h i g h - b o i l i n g l i q u i d s (3). T h e five c h a r a c t e r i s t i c constants w e r e o b t a i n e d u s i n g t h e
In Equations of State in Engineering and Research; Chao, K., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
17.
Refrigerant
KUDCHADKER
309
500
above data a n d the nonlinear regression p r o g r a m f r o m the T h e r m o d y n a m i c s R e s e a r c h C e n t e r c o m p u t e r p r o g r a m file. T h e s a t u r a t e d a n d s u p e r h e a t e d p r o p e r t i e s w e r e c o m p u t e d f r o m 0.2 t o 100 b a r a n d f r o m 220 t o 540 Κ u s i n g t h e f o r m u l a e g i v e n i n R e f . 4 a n d a r e r e p o r t e d i n T a b l e s I I a n d I I I . T h e p r o p e r t i e s are t h e c o m p r e s s i o n f a c t o r Z , t h e f u g a c i t y coeffi c i e n t φ, t h e r e s i d u a l e n t h a l p y (H — H )/RT,
a n d residual entropy (S —
id
S ) / R . T h e i d e a l gas t h e r m o d y n a m i c p r o p e r t i e s r e q u i r e d t o c a l c u l a t e t h e i d
a b s o l u t e v a l u e s of e n t h a l p y a n d e n t r o p y a r e r e p o r t e d i n T a b l e I V . T h e s e are c a l c u l a t e d f o r R - 5 0 0 u s i n g t h e f o l l o w i n g s t a n d a r d f o r m u l a e f o r a m i x
Downloaded by UNIV OF ARIZONA on December 6, 2012 | http://pubs.acs.org Publication Date: December 1, 1979 | doi: 10.1021/ba-1979-0182.ch017
t u r e f r o m its p u r e c o m p o n e n t d a t a : (ff
i d
H° )
-
(Sid _
= y (H"
0 m
S
o
o
)
m
-
A
_
V
A
S
O
A
+
V
H )
+ y {H«
Q
0 A
B
S
O
B
-
B
_
V
A
R
L
N
X
A
_
H\)
B
V
B
R
L
N
Χ
Β
w h e r e m is R - 5 0 0 , A is 1,1-difluoroethane, Β is d i f l u o r o d i c h l o r o m e t h a n e , y is t h e m o l e f r a c t i o n a n d C ° is h e a t c a p a c i t y at constant pressure. T h e p
i d e a l gas t h e r m o d y n a m i c p r o p e r t i e s of 1,1-fluoroethane a n d d i f l u o r o d i c h l o r o m e t h a n e w e r e t a k e n f r o m R e f . 3. T h e reference state is t h e i d e a l gas at 1.01325 b a r a n d 0 K . Table II.
Properties of Saturated L i q u i d and Vapor of R-500
τ
ρ
(Κ)
(bar)
220 230 233.15 239.67 240 250 260 270 273.15 280 290 298.15 300 310 320 330 340 350 360 370 378.65
0.3922 0.6495 0.7539 1.01325 1.0272 1.5610 2.291 3.259 3.621 4.512 6.098 7.672 8.068 10.47 13.37 16.83 20.90 25.68 31.25 37.74 44.26
Volume,m
3
kmol'
1
Liquid
Vapor
0.0717 0.0731 0.0736 0.0746 0.0746 0.0762 0.0778 0.0796 0.0802 0.0816 0.0837 0.0857 0.0862 0.0890 0.0922 0.0960 0.101 0.107 0.116 0.130 0.200
45.844 28.721 25.011 19.004 18.765 12.706 8.870 6.357 5.751 4.659 3.479 2.774 2.638 2.025 1.568 1.220 0.948 0.731 0.552 0.392 0.200
(Ή Liquid -11.75 -10.95 -10.72 -10.25 -10.23 -9.563 -8.950 -8.380 -8.210 -7.851 -7.355 -6.973 -6.889 -6.448 -6.027 -5.621 -5.223 -4.824 -4.406 -3.921 -2.884
W*)/RT Vapor -0.057 -0.082 -0.091 -0.111 -0.112 -0.150 -0.196 -0.249 -0.268 -0.312 -0.386 -0.454 -0.470 -0.568 -0.682 -0.816 -0.976 -1.175 -1.435 -1.826 -2.884
0
(S - S " V / R Liquid -11.81 -11.02 -10.78 -10.31 -10.28 -9.607 -8.975 -8.384 -8.205 -7.828 -7.304 -6.896 -6.806 -6.331 -5.874 -5.429 -4.990 -4.548 -4.085 -3.552 -2.469
Vapor -0.040 -0.057 -0.064 -0.078 -0.079 -0.105 -0.137 -0.176 -0.189 -0.220 -0.278 -0.323 -0.335 -0.408 -0.494 -0.598 -0.725 -0.888 -1.109 -1.456 -2.469
This assumes that the azeotropic composition is invariant with temperature and pressure. β
In Equations of State in Engineering and Research; Chao, K., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1979.
310
EQUATIONS
Table III. Η - H T(K)
Ζ
Φ
Downloaded by UNIV OF ARIZONA on December 6, 2012 | http://pubs.acs.org Publication Date: December 1, 1979 | doi: 10.1021/ba-1979-0182.ch017
Ρ (bar) 220.00 230.00 233.15 239.67 240.00 250.00 260.00 270.00 273.15 280.00 290.00 298.15 300.00 310.00 320.00 330.00 340.00 350.00 360.00 370.00 378.65 380.00 400.00 420.00 440.00 460.00 480.00 500.00 520.00 540.00
.9914 .9926 .9929 .9935 .9936 .9944 .9951 .9956 .9958 .9961 .9965 .9968 .9969 .9972 .9975 .9977 .9979 .9981 .9982 .9984 .9985 .9985 .9987 .9989 .9991 .9992 .9993 .9994 .9995 .9995
(bar)
STATE
Properties S-S
i
