- Email: [email protected]
Derived thermodynamic design data for heat pump systems operating on R 506
Heat RecoverySystemsVol. 2, No. 5/6. pp. 463 to 473. 1982 Printed in Great Britain.
DERIVED
0198-7593,82:050463-11503.t~ 0 Pergamon Press Ltd
THERMODYNAMIC DESIGN PUMP SYSTEMS OPERATING
DATA FOR ON R506
HEAT
T. O. OMIDEYI, S. DEVOTTA, F. A. WATSON and F. A. HOLLAND Department of Chemical Engineering, University of Salford, Salford M5 4WT, U.K.
(Received for publication 18 May 1982) Abstract--The theoretical Rankine coefficient of performance and the compression ratios have been presented for heat pump systems operating on R506. These values are listed in tabular form for temperature lifts of 10-75°C and for condensing temperatires of 15-130~C in 5°C increments. Several graphs have been drawn to illustrate the feasible operating range for R506 heat pump systems. The derived thermodynamic data can be used for the rapid preliminary design of heat pump systems operating on R506.
NOMENCLATURE (COPh
(CR) Hx Pco PEV Tco
To Tev Ts q~x
Rankine coefficient of performance of the heat pump system compression ratio of the heat pump enthalpy per unit mass at state condition X pressure in the condenser of the heat pump system pressure in the evaporator of the heat pump system temperature of the working fluid in the condenser temperature of the heat sink fluid from the heat pump system temperature of the working fluid in the evaporator temperature of the heat source fluid to the heat pump system entropy per unit mass at state condition X
dimensionless dimensionless [kJ kg- 1] [bar] [bar] [K or ~C] [K or C ] [K or C ] [K or C ] [kJ kg- 1 K - 1].
INTRODUCTION
R506 Is ONE of the potentially suitable working fluids for heat pump systems. It is an azeotropic mixture of 55.1~o R31 (CH2CIF) and 44.9% Rl14 (C2C12F4) by weight. The critical temperature and pressure are 142.0°C and 51.64 bar, respectively. Physical data for R506 are listed in Table 1. DERIVED THERMODYNAMIC DESIGN DATA
The operation of a mechanical vapour compression heat pump approximates closely to the Rankine cycle. The ideal Rankine cycle is illustrated in Fig. 1 which is a plot of pressure P against enthalpy per unit mass H for R506. With reference to Fig. 1, the theoretical Rankine coefficient of performance of a heat pump can be defined as
(COP)R =
HD1 -- HD3 HDI -- Hs2
(1)
Since the compression from $2 to D1 is isentropic ~bDl = ~bs2 where 4' is the entropy per unit mass. The enthalpy per unit mass of the superheated vapour HD1 can be approximately related to the enthalpy per unit mass of the saturated vapour at point D2 by the equation HD1 = HD2 + (t~S2 -- t~D2)Tco.
(2)
Equations (1) and (2) can be used to calculate (COP)Rvalues for any desired condensing temperature Tco and gross temperature lift (Tco - TEV) from the saturation properties of the chosen working fluid. 463
-3
13.750 15.979 18.471
1298.4 1284.7 1270.8 1256.5
1211,8
2 7989
q 2943
3 8543
4.4857
5.1q25
5.9811
6.8598
95
20
2~
~O
?q
40
4~
8.50'~
1180.4
10.O8OO
11.3731
12.7889
55
60
65
70 1129.6
1147.1
1164.O
1196.4
7.8323
B.9018
50
24.403
1227.2
52.278
46.310
40.957
36.134
31.795
27.897
21.271
124].9
}1.779
10.O43
1125.2 ] ~]1.9
1 982~
7.167
vapour
kq m
2 3628
1~.~
1 iq,~id
density
5
1 651]
O
('0
b,]r
P
C
CO
]O
o
T
O.24463
0.24558
0.24611
0.24635
0.24634
0.24589
O.24509
0,24411
0.24285
0,24121
0.23959
184.682
189.338
193.692
197.861
201.829
205.612
209.222
212.688
216.Oli
219.199
222.242
225.184
227.985
0,23762
2]0.706
O.23527
2~3.285
KJ kg -I
9.6549
8.7683
7.9330
7.1496
6.4171
5.7360
5.1057
4.5241
3.990
3.5025
3.0557
2.6524
2.2896
1.9630
1.6720
MJ m -3 vapour
]atent heat
O.23297
0.23040
bar m3kq -I
PV
Table 1. Physical data for R506
365.330
363.580
361.673
359.702
357.604
355.457
353,210
350.913
348,537
346.111
343.632
341.104
338.540
335.935
333.285
KJ kg -I
enthalpy of saturated vapour mass
fluid
of
5.4147
5. 2816
5. 1628
5.0541
4.9547
4.8635
4.7796
4.7017
4.6294
4. 5621
4.4996
4. 4408
4. 3863
4.3345
4. 2866
kg Mj-I
working
>
c~
>
>
?
C
©
4~
1111.4 ]092.7
14.324~]
16.~)13
75
38.5527
42.O731
45.7888
47.3352
51.6680
125
130
]35
137
141.7
critical
35.2746
29.3505
]20
26.6903
]05
32.2124
956.8
24.2165
IOO
I15
983.3
21.9202
95
551.O
640,I
7]9.6
821.3
857.7
896.3
927.8
1OO7.7
1030.8
1052.5
19.7929
90
1073.1
17.8227
85
liquid
bar
C
-3
551.O
300.279
276.687
233.629
2OO.O10
174.116
152.882
134,834
119.443
106.O51
94.252
83.832
74.573
66.324
58.913
vapour
density kg m
PCO
TCO
0.09377
0.15764
0.16549
0.18008
0.19275
O.20259
0.21070
0.21768
0.22346
0.22835
0.23257
0.23610
0.2]900
0.24126
O.24315
bar m3kg-I
PV
O.OOO
64,206
72.364
89,152
103.631
115.287
125.496
134.568
142.778
150.158
156.979
163.287
169.163
174.665
179.841
-I KJ kg
O.OOO
19.2796
20.O221
20.8285
20.7272
20.0733
19.1861
18.1444
17.O538
15.9244
14.7956
13.6887
12.6150
11.5845
10.5950
-3 MJ m vapour
latent heat
Table 1. C o n t i n u e d
321.316
358. 325
361.331
365.931
369. 339
371.270
372.416
372.926
372.948
372,592
371.924
3?0.997
369.834
368. 505
366.990
KJ kg -I
enthalpy of saturated vapour -1
15. 5749
13.8190
ii. 2168
9.6496
8.6740
7.9684
7.4312
7.0039
6.6597
6.3703
6.1242
5.9114
5.7252
5. 5605
kg MJ
mass of working fluid
t~
5
t~
o
<=
~L
6.58
5.79
5.16
4.66
4.24
40.0
45.0
50.0
55.0
60.0
3,31
7.59
35.0
75.0
8.95
30.0
3.88
10.85
25.0
3.57
]3.68
20.0
70.0
18.47
65.0
27.94
2.799
15.0
15.0
ar)
I0.0
C
3.35
3.62
3.93
4.29
4.71
5.23
5,87
6.66
7.69
9.06
10.96
13.86
18,62
28.02
3.294
20.0
3~39
3.67
3.98
4.34
4.78
5.31
5.95
6.76
7.81
9.19
11.16
14.08
18.92
28.80
3.854
25.0
3.44
3.70
4.02
4.39
4.84
5.37
6.03
6.85
7.90
9.32
11.29
14.22
19.22
29.36
4.486
30.0
3.47
3.74
4.07
4.45
4.90
5.44
6.11
6.93
8.01
9.44
11.43
14.48
19.64
29.65
5.193
35.0
3.50
3 .~8
4.11
4.49
4.95
5.50
6.17
7.02
8.10
9.53
11.59
14.71
19.77
30.09
5.981
40.0 ......
3.53
3.82
4.15
4.54
5.00
5.54
6.23
7.07
8.15
9.63
ii.71
14.74
19.88
29.92
6.860
45.0
3.57
3.85
4.19
4.58
5.04
5.61
6.29
7.14
8.26
9.77
11.83
14.97
20.12
30.50
7.832
50.0
8.902
55.0
10.080
60.0
11.373
65.0
Table 2. Theoretical R a n k i n e c o e f l i c i e n t s o f p e r ~ r m a n c e ( C O l ' l ~ f o r a r a n g e o f l i ~ s a n d condensinglemperaluresfor R506
3.67
3.97
4.32
4.72
5.22
5.81
6.53
7.44
8.60
I0.17
12.45
15.77
21.50
32.44
12.789
70.0
c~
"v, >
© ©
C
6.53
5.81
5.23
4.73
4.32
3.97
3.67
45.0
50.0
55.0
60.0
65.0
70.0
75.O
]O.18
30.0
8.58
]2.34
25.0
7.42
I%.67
35.0
20.90
]5.0
20.0
40.0
~1.74
10.0
l,~a:) ,.
7q.O
|4.325
"~0
o
(Tco_TEv) O c ~
~ O
3.6R
3.98
4.33
4.75
5.23
5.82
6.54
7.44
8.64
10.19
12.40
15.54
20.99
30.96
16.OO1
80.0
3.68
3.99
4.35
4.76
5.25
5.84
6.56
7.50
8.67
10.26
12.37
15.69
20.82
32.47
17.82]
85.0
3.68
3.99
4.34
4.76
5.24
5.83
6.58
7.48
8.68
10.18
12.39
15.48
21.30
32.57
19.793
90.0
3.68
3.98
4.33
4.74
5.23
5.84
6.56
7.49
8.62
10.19
12.26
15.77
21.4|
32.35
21.920
95.0
Table 3. Theoretical Rankine coefficients of performance
3.66
3.97
4.32
4.74
5.25
5.84
6.59
7.47
8.67
10.18
12.58
16.06
21.77
33.78
24.217
IOO.O
[ C O P ) R for
3.62
3.91
4.26
4.68
5.16
5.75
6.44
7.34
8.42
10.O5
12.24
15.41
20.81
31~32
26.690
105.O
3.58
3.88
4.23
4.64
5.12
5.68
6.40
7.25
8.48
10.O5
12.19
15.50
20.95
30.59
29.351
I IIO.O
3.53
3.83
4.17
4.58
5.04
5.62
6.29
7.24
8.41
9.93
12.13
15.42
20.35
33.32
32.212
115.O
3.45
3.74
4.08
4.46
4.93
5.46
6.20
7.08
8.19
9.71
11.83
14.70
20.87
31.26
35.275
120.O
3.35
3.63
3.94
4.33
4.76
5.34
6.02
6.85
7.96
9.42
11.28
14.84
19.81
29.57
38.553
125.O
a range of lifts and condensing temperatures for R506
3.19
3.44
3.75
4.09
4.55
5.07
5.69
6.49
7.51
8.74
10.92
13.61
17.99
27.11
42.073
130.O
O
--4
3
O°C
I
23.983
27.633
~2. 138
75.0
18.049
20.499
2 ~ 478
70.0
13.779
15.427
17.416
65.0
10.646
11.777
I 3. 107
60.0
8.32]
9.100
10.006
55.0
6.577
7.112
7.731
50.0
5.249
5.621
6.043
45.0
4.233
4.486
4.776
40.O
3.442
3.812
35.0
3.618
3.074
2.823
30.O
2.334
2.942
2.5OO
25.O
2.413
2.050
1.944
20.0
].631
].995
1.695
15.0
1.662
].412
]0.0
1.377
2.7~9
].394
25.0
3.854
20.0
3.294
15.O
!lTco_TevlOc~
",~bar:
21.006
16.036
12.390
9.684
7.654
6.109
4.926
4.005
3.285
2.716
2.263
].898
1.603
1.362
4.486
30.0
18.564
]4.343
11.211
8.860
7.072
5.703
4.637
3.803
3.145
2.619
2.198
1.855
1.576
1.347
5.193
35.0
16.521
12.g13
10.206
8.146
6.569
5.342
4.381
3.622
3.0]7
2.531
2.137
1.816
1.552
1.333
5.981
40.0
14.8]0
11.705
9.343
7.534
6.127
5.024
4.154
3.461
2.903
2.451
2.082
1.780
1.529
1.321
6.860
45.0
]3.364
10.667
8.602
6.995
5.737
4.743
3.951
3.315
2.798
2.378
2.032
1.746
1.508
1.310
7.832
50.0
8.902
55.0
10.080
60.0
Table 4. Compression ratio [CRI for a range of lifts and condensing temperatures for R506
11.373
65.0
9.367
7.745
6.422
5.413
4. 569
3.882
3.318
2.851
2.463
2.138
1.864
1.633
1.437
1. 269
12.789
70.0 ©
7/
"r
r~ -<
>.
>
© ~r
2.395
2.759
3.193
35.0
40.0
45.0
5.118
6.063
7.226
8.675
60.0
65.0
7O.O
75.0
3.717
2.088
30.0
4.348
1.829
25.0
55.0
1.609
20.0
50.0
1.421
5
15.0
14.1
75.0
1.260
at)
lo.o
C
4.624 5.410 6.368 7.543
5.717
6.772
8.072
2.598
2.675
4.857
2.276
2.333
3.973
2.002
2.043
4.152
1.768
1.798
2.980
1.567
1.587
3.432
1.394
1.407
3.082
1.244
1.251
3.567
]7.823
85.0
16.001
80.0
7.072
6.008
5.135
4.412
3.812
3.309
2.885
2.527
2.223
1.964
1.740
1.548
1.382
1.237
19.793
90.0
6.654
5.687
4.887
4.221
3.665
3.195
2.799
2.462
2.175
1.927
1.714
1.530
1.370
1.230
21.920
95.0
6.283
5.399
4.664
4.049
3.530
3.092
2.720
2.402
2.129
1.894
1.691
1.513
1.359
1.223
24.217
I00.0
5.950
5.140
4.462
3.891
3.408
2.998
2.648
2.347
2.087
1.863
1.668
1.498
1.348
1.218
26.690
i05,0
5.652
4.907
4.279
3.747
3.297
2.912
2.581
2.295
2.049
1.834
1.647
1.483
1.339
1.212
29.351
II0.0
5.386
4.696
4.113
3.619
3.176
2.832
2.519
2.249
2.013
1.807
1.627
1.470
1.330
1.207
32,212
115.0
5.142
4.504
3.963
3.499
3.102
2.758
2.462
2.204
1.979
1.782
1.609
1.457
1.322
1.202
35.275
120,0
Table 5. Compression ratio(CR) f o r a r a n g e ofliftsand condensing temperatures ~ r R506
4.922
4.331
3.825
3.390
3.015
2.691
2.409
2.163
1.948
1.759
1.592
1.444
1.314
1.197
38.553
125.0
4.726
4.174
3.699
3.290
3.937
2.629
2.361
2.126
1.919
1.737
1.576
1.433
1.306
1.193
42.073
130.0
o
3
470
T. O, OMIDEYI. S. D E v O ] l a . F. A. VV.A]so\ and F. A. }]()l I ",',J~
60 50 40 30
T = tO0°C
20
D3 ./
.
_S_ o,-
75°C
D2.
D/
50"C i
5
---
,4
25°C
IO°C
3 - -
100
- -
----Sli
;2
I
1
150
200
EnthoLPy
L
250
I
I
H,
kJ
~00
per unit
moss
i
L
400
353 kg '
Fig. 1.
20 Too
100°C
=
Pco = 24.22 bet
o -15 o
E E z .
.
.
.
.
.
.
L-
9
I
o
I
g
I I
- I0 ~_
&
So
u
I I I I
I I0
20
30
40
Temperature l i f t I 0
,
,
50
60
( Too T[v),
oP
70
°C
I I I i J IO 20 50 40 50 Temperoture l i f t (TD-T s) °C, with 2~)°C drop in heot exchongers
Fig. 2.
Derived thermodynamic design data
471 2C~
20 ,
Condensing temDeroture
Tco = 7 0 % Tco = IO'
13
E v 0
IC Too = 7 0 o c
g
\J
o 5 c
c~
p-
i I L i I 20 30 40 50 GO Temperature L i f t (Tco-T~v), *C
i 70
Fig. 3.
~
.~
Temperature Lift.
I"~
(TC°~oiiilnliii°iemperature
t5
~
E_
Tco= iOoC
~c ~o
V "'\ ~
5
8
0
i 2
[
[
Fig. 4. H.R.S. 2 5 6
I
~
3 4 5 6 Compression r a t i o (CR), dimensw~nkess
I 7
472
T . O . OMIDEYL S. DEVOTTA. F. A, WATSON and F. A Ho~_t ,'~>,T)
( Tcc -
"6
TEv) = 25oc
9
( Too- TEv ) = 40"C
g
\
I.-
\ 3
30
50
I
i
I
70
90
I tO
Condensing temperature Tco,
130
°C
Fig. 5.
Ln
E
~o o
o
~30
50 70 90 Conclet~sinQt~atufe
Fig. 6.
I I0 Fco, oC
130
Derived thermodynamic design data
473
The theoretical Rankine coefficient of performance (COP)R and the compression ratio (CR), which is the ratio of the corresponding pressures in the condenser and evaporator Pco/PEv, have been calculated for R506 for temperature lifts of 10-75°C and for condensing temperatures of 15-130°C in 5°C increments. All the basic calculations have been taken from published tables Eli. Tables 2 and 3 list the calculated (COP)R values and Tables 4 and 5 the calculated (CR) values. Figures 2-6 are plotted from the data listed in the tables. DISCUSSION OF DERIVED DESIGN DATA Figure 2 shows the variation of the compression ratio (CR) and the theoretical Rankine coefficient of performance (COP)R with gross temperature lift (Tco - TEV) for a condensing temperature Tco of 100°C and a condensing pressure Pco of 24.2 hour. The effective temperature lift will be reduced by 20°C if there is a temperature drop of 10°C in each of the heat exchangers. Figure 3 shows that (CR) values for a given temperature lift are extremely sensitive to the condensing temperature. In contrast, the (COP)R values are almost independent of the condensing temperature. Figure 4, which is a plot of (COP)R against (CR) for various temperature lifts, implies that relatively high coefficients of performance are only possible for relatively low temperature lifts and compression ratios. Figure 5 shows that for a given temperature lift (COP)R initially increases with condensing temperature and then decreases after reaching maximum in the region of 90°C. The maximum is more pronounced for lower temperature lifts. Figure 6 shows the variation of compression ratio with condensing temperature. Figure 6 clearly indicates the upper limit of the possible temperature lifts resulting from any practical limit to the compression ratio. REFERENCE
1. ASHRAEHandbook 1977Fundamentalsand Product Director)'.American Societyof Heating, Refrigerating and Air Conditioning Engineers, New York, pl6.41 (1977).
DERIVED
0198-7593,82:050463-11503.t~ 0 Pergamon Press Ltd
THERMODYNAMIC DESIGN PUMP SYSTEMS OPERATING
DATA FOR ON R506
HEAT
T. O. OMIDEYI, S. DEVOTTA, F. A. WATSON and F. A. HOLLAND Department of Chemical Engineering, University of Salford, Salford M5 4WT, U.K.
(Received for publication 18 May 1982) Abstract--The theoretical Rankine coefficient of performance and the compression ratios have been presented for heat pump systems operating on R506. These values are listed in tabular form for temperature lifts of 10-75°C and for condensing temperatires of 15-130~C in 5°C increments. Several graphs have been drawn to illustrate the feasible operating range for R506 heat pump systems. The derived thermodynamic data can be used for the rapid preliminary design of heat pump systems operating on R506.
NOMENCLATURE (COPh
(CR) Hx Pco PEV Tco
To Tev Ts q~x
Rankine coefficient of performance of the heat pump system compression ratio of the heat pump enthalpy per unit mass at state condition X pressure in the condenser of the heat pump system pressure in the evaporator of the heat pump system temperature of the working fluid in the condenser temperature of the heat sink fluid from the heat pump system temperature of the working fluid in the evaporator temperature of the heat source fluid to the heat pump system entropy per unit mass at state condition X
dimensionless dimensionless [kJ kg- 1] [bar] [bar] [K or ~C] [K or C ] [K or C ] [K or C ] [kJ kg- 1 K - 1].
INTRODUCTION
R506 Is ONE of the potentially suitable working fluids for heat pump systems. It is an azeotropic mixture of 55.1~o R31 (CH2CIF) and 44.9% Rl14 (C2C12F4) by weight. The critical temperature and pressure are 142.0°C and 51.64 bar, respectively. Physical data for R506 are listed in Table 1. DERIVED THERMODYNAMIC DESIGN DATA
The operation of a mechanical vapour compression heat pump approximates closely to the Rankine cycle. The ideal Rankine cycle is illustrated in Fig. 1 which is a plot of pressure P against enthalpy per unit mass H for R506. With reference to Fig. 1, the theoretical Rankine coefficient of performance of a heat pump can be defined as
(COP)R =
HD1 -- HD3 HDI -- Hs2
(1)
Since the compression from $2 to D1 is isentropic ~bDl = ~bs2 where 4' is the entropy per unit mass. The enthalpy per unit mass of the superheated vapour HD1 can be approximately related to the enthalpy per unit mass of the saturated vapour at point D2 by the equation HD1 = HD2 + (t~S2 -- t~D2)Tco.
(2)
Equations (1) and (2) can be used to calculate (COP)Rvalues for any desired condensing temperature Tco and gross temperature lift (Tco - TEV) from the saturation properties of the chosen working fluid. 463
-3
13.750 15.979 18.471
1298.4 1284.7 1270.8 1256.5
1211,8
2 7989
q 2943
3 8543
4.4857
5.1q25
5.9811
6.8598
95
20
2~
~O
?q
40
4~
8.50'~
1180.4
10.O8OO
11.3731
12.7889
55
60
65
70 1129.6
1147.1
1164.O
1196.4
7.8323
B.9018
50
24.403
1227.2
52.278
46.310
40.957
36.134
31.795
27.897
21.271
124].9
}1.779
10.O43
1125.2 ] ~]1.9
1 982~
7.167
vapour
kq m
2 3628
1~.~
1 iq,~id
density
5
1 651]
O
('0
b,]r
P
C
CO
]O
o
T
O.24463
0.24558
0.24611
0.24635
0.24634
0.24589
O.24509
0,24411
0.24285
0,24121
0.23959
184.682
189.338
193.692
197.861
201.829
205.612
209.222
212.688
216.Oli
219.199
222.242
225.184
227.985
0,23762
2]0.706
O.23527
2~3.285
KJ kg -I
9.6549
8.7683
7.9330
7.1496
6.4171
5.7360
5.1057
4.5241
3.990
3.5025
3.0557
2.6524
2.2896
1.9630
1.6720
MJ m -3 vapour
]atent heat
O.23297
0.23040
bar m3kq -I
PV
Table 1. Physical data for R506
365.330
363.580
361.673
359.702
357.604
355.457
353,210
350.913
348,537
346.111
343.632
341.104
338.540
335.935
333.285
KJ kg -I
enthalpy of saturated vapour mass
fluid
of
5.4147
5. 2816
5. 1628
5.0541
4.9547
4.8635
4.7796
4.7017
4.6294
4. 5621
4.4996
4. 4408
4. 3863
4.3345
4. 2866
kg Mj-I
working
>
c~
>
>
?
C
©
4~
1111.4 ]092.7
14.324~]
16.~)13
75
38.5527
42.O731
45.7888
47.3352
51.6680
125
130
]35
137
141.7
critical
35.2746
29.3505
]20
26.6903
]05
32.2124
956.8
24.2165
IOO
I15
983.3
21.9202
95
551.O
640,I
7]9.6
821.3
857.7
896.3
927.8
1OO7.7
1030.8
1052.5
19.7929
90
1073.1
17.8227
85
liquid
bar
C
-3
551.O
300.279
276.687
233.629
2OO.O10
174.116
152.882
134,834
119.443
106.O51
94.252
83.832
74.573
66.324
58.913
vapour
density kg m
PCO
TCO
0.09377
0.15764
0.16549
0.18008
0.19275
O.20259
0.21070
0.21768
0.22346
0.22835
0.23257
0.23610
0.2]900
0.24126
O.24315
bar m3kg-I
PV
O.OOO
64,206
72.364
89,152
103.631
115.287
125.496
134.568
142.778
150.158
156.979
163.287
169.163
174.665
179.841
-I KJ kg
O.OOO
19.2796
20.O221
20.8285
20.7272
20.0733
19.1861
18.1444
17.O538
15.9244
14.7956
13.6887
12.6150
11.5845
10.5950
-3 MJ m vapour
latent heat
Table 1. C o n t i n u e d
321.316
358. 325
361.331
365.931
369. 339
371.270
372.416
372.926
372.948
372,592
371.924
3?0.997
369.834
368. 505
366.990
KJ kg -I
enthalpy of saturated vapour -1
15. 5749
13.8190
ii. 2168
9.6496
8.6740
7.9684
7.4312
7.0039
6.6597
6.3703
6.1242
5.9114
5.7252
5. 5605
kg MJ
mass of working fluid
t~
5
t~
o
<=
~L
6.58
5.79
5.16
4.66
4.24
40.0
45.0
50.0
55.0
60.0
3,31
7.59
35.0
75.0
8.95
30.0
3.88
10.85
25.0
3.57
]3.68
20.0
70.0
18.47
65.0
27.94
2.799
15.0
15.0
ar)
I0.0
C
3.35
3.62
3.93
4.29
4.71
5.23
5,87
6.66
7.69
9.06
10.96
13.86
18,62
28.02
3.294
20.0
3~39
3.67
3.98
4.34
4.78
5.31
5.95
6.76
7.81
9.19
11.16
14.08
18.92
28.80
3.854
25.0
3.44
3.70
4.02
4.39
4.84
5.37
6.03
6.85
7.90
9.32
11.29
14.22
19.22
29.36
4.486
30.0
3.47
3.74
4.07
4.45
4.90
5.44
6.11
6.93
8.01
9.44
11.43
14.48
19.64
29.65
5.193
35.0
3.50
3 .~8
4.11
4.49
4.95
5.50
6.17
7.02
8.10
9.53
11.59
14.71
19.77
30.09
5.981
40.0 ......
3.53
3.82
4.15
4.54
5.00
5.54
6.23
7.07
8.15
9.63
ii.71
14.74
19.88
29.92
6.860
45.0
3.57
3.85
4.19
4.58
5.04
5.61
6.29
7.14
8.26
9.77
11.83
14.97
20.12
30.50
7.832
50.0
8.902
55.0
10.080
60.0
11.373
65.0
Table 2. Theoretical R a n k i n e c o e f l i c i e n t s o f p e r ~ r m a n c e ( C O l ' l ~ f o r a r a n g e o f l i ~ s a n d condensinglemperaluresfor R506
3.67
3.97
4.32
4.72
5.22
5.81
6.53
7.44
8.60
I0.17
12.45
15.77
21.50
32.44
12.789
70.0
c~
"v, >
© ©
C
6.53
5.81
5.23
4.73
4.32
3.97
3.67
45.0
50.0
55.0
60.0
65.0
70.0
75.O
]O.18
30.0
8.58
]2.34
25.0
7.42
I%.67
35.0
20.90
]5.0
20.0
40.0
~1.74
10.0
l,~a:) ,.
7q.O
|4.325
"~0
o
(Tco_TEv) O c ~
~ O
3.6R
3.98
4.33
4.75
5.23
5.82
6.54
7.44
8.64
10.19
12.40
15.54
20.99
30.96
16.OO1
80.0
3.68
3.99
4.35
4.76
5.25
5.84
6.56
7.50
8.67
10.26
12.37
15.69
20.82
32.47
17.82]
85.0
3.68
3.99
4.34
4.76
5.24
5.83
6.58
7.48
8.68
10.18
12.39
15.48
21.30
32.57
19.793
90.0
3.68
3.98
4.33
4.74
5.23
5.84
6.56
7.49
8.62
10.19
12.26
15.77
21.4|
32.35
21.920
95.0
Table 3. Theoretical Rankine coefficients of performance
3.66
3.97
4.32
4.74
5.25
5.84
6.59
7.47
8.67
10.18
12.58
16.06
21.77
33.78
24.217
IOO.O
[ C O P ) R for
3.62
3.91
4.26
4.68
5.16
5.75
6.44
7.34
8.42
10.O5
12.24
15.41
20.81
31~32
26.690
105.O
3.58
3.88
4.23
4.64
5.12
5.68
6.40
7.25
8.48
10.O5
12.19
15.50
20.95
30.59
29.351
I IIO.O
3.53
3.83
4.17
4.58
5.04
5.62
6.29
7.24
8.41
9.93
12.13
15.42
20.35
33.32
32.212
115.O
3.45
3.74
4.08
4.46
4.93
5.46
6.20
7.08
8.19
9.71
11.83
14.70
20.87
31.26
35.275
120.O
3.35
3.63
3.94
4.33
4.76
5.34
6.02
6.85
7.96
9.42
11.28
14.84
19.81
29.57
38.553
125.O
a range of lifts and condensing temperatures for R506
3.19
3.44
3.75
4.09
4.55
5.07
5.69
6.49
7.51
8.74
10.92
13.61
17.99
27.11
42.073
130.O
O
--4
3
O°C
I
23.983
27.633
~2. 138
75.0
18.049
20.499
2 ~ 478
70.0
13.779
15.427
17.416
65.0
10.646
11.777
I 3. 107
60.0
8.32]
9.100
10.006
55.0
6.577
7.112
7.731
50.0
5.249
5.621
6.043
45.0
4.233
4.486
4.776
40.O
3.442
3.812
35.0
3.618
3.074
2.823
30.O
2.334
2.942
2.5OO
25.O
2.413
2.050
1.944
20.0
].631
].995
1.695
15.0
1.662
].412
]0.0
1.377
2.7~9
].394
25.0
3.854
20.0
3.294
15.O
!lTco_TevlOc~
",~bar:
21.006
16.036
12.390
9.684
7.654
6.109
4.926
4.005
3.285
2.716
2.263
].898
1.603
1.362
4.486
30.0
18.564
]4.343
11.211
8.860
7.072
5.703
4.637
3.803
3.145
2.619
2.198
1.855
1.576
1.347
5.193
35.0
16.521
12.g13
10.206
8.146
6.569
5.342
4.381
3.622
3.0]7
2.531
2.137
1.816
1.552
1.333
5.981
40.0
14.8]0
11.705
9.343
7.534
6.127
5.024
4.154
3.461
2.903
2.451
2.082
1.780
1.529
1.321
6.860
45.0
]3.364
10.667
8.602
6.995
5.737
4.743
3.951
3.315
2.798
2.378
2.032
1.746
1.508
1.310
7.832
50.0
8.902
55.0
10.080
60.0
Table 4. Compression ratio [CRI for a range of lifts and condensing temperatures for R506
11.373
65.0
9.367
7.745
6.422
5.413
4. 569
3.882
3.318
2.851
2.463
2.138
1.864
1.633
1.437
1. 269
12.789
70.0 ©
7/
"r
r~ -<
>.
>
© ~r
2.395
2.759
3.193
35.0
40.0
45.0
5.118
6.063
7.226
8.675
60.0
65.0
7O.O
75.0
3.717
2.088
30.0
4.348
1.829
25.0
55.0
1.609
20.0
50.0
1.421
5
15.0
14.1
75.0
1.260
at)
lo.o
C
4.624 5.410 6.368 7.543
5.717
6.772
8.072
2.598
2.675
4.857
2.276
2.333
3.973
2.002
2.043
4.152
1.768
1.798
2.980
1.567
1.587
3.432
1.394
1.407
3.082
1.244
1.251
3.567
]7.823
85.0
16.001
80.0
7.072
6.008
5.135
4.412
3.812
3.309
2.885
2.527
2.223
1.964
1.740
1.548
1.382
1.237
19.793
90.0
6.654
5.687
4.887
4.221
3.665
3.195
2.799
2.462
2.175
1.927
1.714
1.530
1.370
1.230
21.920
95.0
6.283
5.399
4.664
4.049
3.530
3.092
2.720
2.402
2.129
1.894
1.691
1.513
1.359
1.223
24.217
I00.0
5.950
5.140
4.462
3.891
3.408
2.998
2.648
2.347
2.087
1.863
1.668
1.498
1.348
1.218
26.690
i05,0
5.652
4.907
4.279
3.747
3.297
2.912
2.581
2.295
2.049
1.834
1.647
1.483
1.339
1.212
29.351
II0.0
5.386
4.696
4.113
3.619
3.176
2.832
2.519
2.249
2.013
1.807
1.627
1.470
1.330
1.207
32,212
115.0
5.142
4.504
3.963
3.499
3.102
2.758
2.462
2.204
1.979
1.782
1.609
1.457
1.322
1.202
35.275
120,0
Table 5. Compression ratio(CR) f o r a r a n g e ofliftsand condensing temperatures ~ r R506
4.922
4.331
3.825
3.390
3.015
2.691
2.409
2.163
1.948
1.759
1.592
1.444
1.314
1.197
38.553
125.0
4.726
4.174
3.699
3.290
3.937
2.629
2.361
2.126
1.919
1.737
1.576
1.433
1.306
1.193
42.073
130.0
o
3
470
T. O, OMIDEYI. S. D E v O ] l a . F. A. VV.A]so\ and F. A. }]()l I ",',J~
60 50 40 30
T = tO0°C
20
D3 ./
.
_S_ o,-
75°C
D2.
D/
50"C i
5
---
,4
25°C
IO°C
3 - -
100
- -
----Sli
;2
I
1
150
200
EnthoLPy
L
250
I
I
H,
kJ
~00
per unit
moss
i
L
400
353 kg '
Fig. 1.
20 Too
100°C
=
Pco = 24.22 bet
o -15 o
E E z .
.
.
.
.
.
.
L-
9
I
o
I
g
I I
- I0 ~_
&
So
u
I I I I
I I0
20
30
40
Temperature l i f t I 0
,
,
50
60
( Too T[v),
oP
70
°C
I I I i J IO 20 50 40 50 Temperoture l i f t (TD-T s) °C, with 2~)°C drop in heot exchongers
Fig. 2.
Derived thermodynamic design data
471 2C~
20 ,
Condensing temDeroture
Tco = 7 0 % Tco = IO'
13
E v 0
IC Too = 7 0 o c
g
\J
o 5 c
c~
p-
i I L i I 20 30 40 50 GO Temperature L i f t (Tco-T~v), *C
i 70
Fig. 3.
~
.~
Temperature Lift.
I"~
(TC°~oiiilnliii°iemperature
t5
~
E_
Tco= iOoC
~c ~o
V "'\ ~
5
8
0
i 2
[
[
Fig. 4. H.R.S. 2 5 6
I
~
3 4 5 6 Compression r a t i o (CR), dimensw~nkess
I 7
472
T . O . OMIDEYL S. DEVOTTA. F. A, WATSON and F. A Ho~_t ,'~>,T)
( Tcc -
"6
TEv) = 25oc
9
( Too- TEv ) = 40"C
g
\
I.-
\ 3
30
50
I
i
I
70
90
I tO
Condensing temperature Tco,
130
°C
Fig. 5.
Ln
E
~o o
o
~30
50 70 90 Conclet~sinQt~atufe
Fig. 6.
I I0 Fco, oC
130
Derived thermodynamic design data
473
The theoretical Rankine coefficient of performance (COP)R and the compression ratio (CR), which is the ratio of the corresponding pressures in the condenser and evaporator Pco/PEv, have been calculated for R506 for temperature lifts of 10-75°C and for condensing temperatures of 15-130°C in 5°C increments. All the basic calculations have been taken from published tables Eli. Tables 2 and 3 list the calculated (COP)R values and Tables 4 and 5 the calculated (CR) values. Figures 2-6 are plotted from the data listed in the tables. DISCUSSION OF DERIVED DESIGN DATA Figure 2 shows the variation of the compression ratio (CR) and the theoretical Rankine coefficient of performance (COP)R with gross temperature lift (Tco - TEV) for a condensing temperature Tco of 100°C and a condensing pressure Pco of 24.2 hour. The effective temperature lift will be reduced by 20°C if there is a temperature drop of 10°C in each of the heat exchangers. Figure 3 shows that (CR) values for a given temperature lift are extremely sensitive to the condensing temperature. In contrast, the (COP)R values are almost independent of the condensing temperature. Figure 4, which is a plot of (COP)R against (CR) for various temperature lifts, implies that relatively high coefficients of performance are only possible for relatively low temperature lifts and compression ratios. Figure 5 shows that for a given temperature lift (COP)R initially increases with condensing temperature and then decreases after reaching maximum in the region of 90°C. The maximum is more pronounced for lower temperature lifts. Figure 6 shows the variation of compression ratio with condensing temperature. Figure 6 clearly indicates the upper limit of the possible temperature lifts resulting from any practical limit to the compression ratio. REFERENCE
1. ASHRAEHandbook 1977Fundamentalsand Product Director)'.American Societyof Heating, Refrigerating and Air Conditioning Engineers, New York, pl6.41 (1977).