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Derived thermodynamic data for heat pump systems operating on R22
Heat Ream'it)' S)'~ems ¥ol. I. No, Z pp. I I I Io 123. 1981 Printed in Great Britain
DERIVED
0198/7593/81/020111-13502,00/0 Pergamon Press Led
THERMODYNAMIC DATA FOR HEAT SYSTEMS OPERATING O N R22
PUMP
K. W. TAI, S. DEVOTTA, F. A. WATSON and F. A. HOLLAND Department of Chemical Engineering, University of Salforcl, Salford M5 4WT, U.K. R. Z Y L L / ~
Abstract--The theoretical Rankine coefficients of performance (COP~ and the compression ratios have been presented for heat pump systems operating on R22. These values are listed in tabular form for temperature lifts of 10--75°C in 5°C increments and condensing temperatures Tea for every degree in the range of 15-85°C. Several graphs have been drawn to illustrate the feasible operating range for R22 heat pump systems. The derived thermodynamic data can be used for the rapid preliminary design of heat pump systems operating on R22.
INTRODUCTION
A VAPOUR compression heat pump, diagrammatically shown in Fig. 1, consists of two heat exchangers, a compressor and an expansion valve. The operation of the system is based on the continuous recycling of the working fluid. The working fluid vapourises in the evaporator heat exchanger at a temperature TEe by extracting heat from a heat source and, after compression, releases its latent heat in the condenser heat exchanger at a temperature Tco to a heat sink. The condensing temperature Tco, the temperature lift (Tco - TEe) and the compression ratio Pco/PEv, which is the ratio of the corresponding pressures in the condenser and evaporator are the critical parameters which determine the feasible operating range of a heat pump with a particular working fluid. R22 is one of the more widely used working fluids, both in refrigeration and heat pump systems. Its chemical formula is CHCIF2 and its critical temperature and pressure are 369.1 K and 49.921 bar respectively. Physical data for R22 are listed in Table 1. The principal disadvantage with R22 is the relatively high condensing pressures Pep which correspond to relatively modest condensation temperatures Tco.
drop
~elivered heat
t
Comoressor
Exponsior~
temperature
vo,.
,,,,.,0_,,
HeOJ' source m
~' __]__~EX _ _ _
t
I
Fig. 1. Simplified diagram of a vapour compression heat pump.
lil
112
R. ZYLLA et al. Table 1. Physical data for R22
TCO
PCO
density kg m -3
PV
latent heat
bar m 3 kg -] oC
bar
liquid
vapour
kJ kg -I
O
4.96256
1285.7
21.1018
0.23517
205.991
5
5.82289
1268.5
24.6544
0.23618
202.029
I0
6.79153
1250.8
28.6757
0.23683
15
7.87684
1232.6
33.2172
20
9.08749
1213.8
25
10.43233
1194.4
30
11.92061
1174.2
35
13 56165
40 45
MJ m -3
vapouz 4.3467
enthalpy of saturated vap°uxl
kJ k a - "
mass of working fluid kg MJ -I
305.991
4.8546
4.9809
307.822
4.9497
197.888
5.6745
309.552
5.0534
0.23713
193.557
6.4294
311.171
5.1664
38.3380
0.23703
189.016
7.2464
312.670
5.2906
44.1055
0.23653
184.247
8.1263
314.039
5.4275
50.5987
0.23559
179.225
9.0685
315.264
5.5796
1153.3
57.9099
0.23418
173.923
10.0718
316.332
5.7497
15.3651
1131.51
66.149
0.23228
168.305
11.1320
317.226
5.9422
17.3409
1108.68
75.453
0.22982
162.327
12.2480
317.926
6.1604
50
19.4994
1084.66
85.989
0.22676
155.934
13.4086
318.406
6.4129
55
21.8510
1059.24
97.973
0.22303
149.054
14.6032
318.631
6.7090
60
24.4068
1032.12
111.695
0.21851
141.588
15.8146
318.556
7.0627
65
27.1779
1002.91
127.555
0.21306
133.399
17.0157
318.113
7.4963
70
30.1759
971.O3
146.149
0.20647
124.284
18.1639
317.201
8.O461 8.7779
75
33.413
935.58
168.434
0.19837
113.922
19.1883
315.652
80
36.902
895.03
196.018
0.18825
101.836
19.9616
313.187
9.8197
85
40.~55
846.39
231.705
0.17546
87.336
20.2361
309.360
11.4500
90
44.686
782.10
283.041
0.15787
68.362
19.3492
302.981
14.6280
95
49.O10
661.17
391.O21
0.12533
34.425
13.4608
288.129
29.0488
49.921
524.79
524.790
0.09513
0.000
0.0OOO
270.470
96.01 CRITICAl
DERIVED THERMODYNAMIC DATA The operation of a conventional vapour compression heat pump i~ based on the Rankine cycle. The ideal Rankine cycle is illustrated in Fig. 2 which is a plot of pressure P against enthalpy per unit mass H for R22. With reference to Fig. 2, the theoretical Rankine coefficient of performance of a heat pump can be defined as (COP). - HD1 -- Hv3 Hol - Hs2'
(I)
~00--
4 0 O -30.0
DI
200 150 -~ 0-"
I00
~
70
~ O.
5.() 3.0 20: 15 ~0'
40
60 80
O0 ~20 ~40 60 80 2 0 0 Z 2 0 Z 4 0 Z S O ~ 3 0 0 3 2 0 Enff~lpy per unit moss H, kJ kg-I
Fig. 2. Pressure against enthalpy per unit mass for R22.
340
Thermodynamic data for heat pump systems operating on R22
II3
Table 2. Theoretical Rankine coemcients of performance ( C O P k for a range of liftsand condensing temperatures for R22
~
(b.:)
15.0
16.0
17.0
16.0
19.o
20.0
21.0
22.0
23.0
24.0
25.u
(TCO-'L'I~, ~
7.877
8o109
8.346
8.588
8.835
9.087
Y.346
9.609
9.878
10.152
10.432
lO.O
27.34
27,42
27.49
27.55
27.61
27.67
27,74
27.81
27.85
27.91
27.98
15.0
18.00
18.05
18.10
18.14
16.18
18.22
18.26
18.31
18.34
18.38
18.42
2U.O
13.34
13.38
13.41
13.44
13.47
13.50
13.53
25.0
10.55
10.58
10.60
I0.63
10.65
10.67
10.70
13.56
13.59
13.62
13.6$
10.72
10.74
lO.7b
10.79
30.o
8.69
8.71
8.73
8.75
8.77
8.79
8.81
e.83
s.e$
8.87
s.e8
35.0
7.37
7.39
7.40
7.42
7.44
7.45
7.47
7.48
7.50
7.S!
7.~3
40.0
6.38
6.39
6.41
6.42
6.44
6.45
6.46
6.48
6.49
6.50
6.51
1*5.0
5.61
5.62
5.64
5.65
5.66
5.67
5.68
5.7U
5.71
5.72
5.73
50.0
5.00
5.01
5.02
5.03
5.04
.5.0$
5.06
5.07
5.08
5.09
s. 10
.55.0
4..50
4.51
4..52
4..53
4°.54
4.5.5
4..56
4..57
4.57
4.S~
4..59
60.0
4.09
4.10
4.11
4.11
4.12
4.13
4.14
4.15
4.1.5
4.16
4.17
6.5.0
3.74
3.75
3.76
3.76
3.77
3.78
3.78
3.79
3.80
3.81
3.81
70.0 ,
3.44
3.4.5
3.46
3.46
3,47
3.48
3.48
3.49
3.50
3.50
3.51
73.0
3.19
3.19
3.20
3,21
3.21
3.22
3.22
3.23
3.24
3.24
3.25
Table 3. Theoretical Rankine coefficients of .performance (COPk for a range of lifts and condensing temperatures for R22
R Z Y L L A el' O•.
114
Table 4 Theoretical Rankine coefficients of performance (COP)R for a range of lifts and condensing temperatures for R22 ~ e o °e
! 35.0
36.0
37.0
13.561
13.909
14.263
1o.0
28.4,
2,.53
28.57
28.63
fT -,r ~ ; r ) c%-T~)oc'~
38.0
39.0
40.0
14.624 14.991 15.365
28.65
28.68
41.0
42.0
43.0
44.0
15.746
16.134
16.529
16.932
28.73
28.76
28.80
28.81
~ 45.0 !
17.341 28.84
15.o
18.75
18.78
18.8o
18.84
18.86
18.87
18.9o
18.92
18.94
18.96
18.97
20.0
13.89
13.91
13.92
13.95
13.96
13.98
14.00
14.01
14.03
14.04
14.04
25.0
10.97
10.99
11.00
11.02
11.03
11.04
11.06
11.07
11.08
11.09
11.10
30.0
9.04
9.05
9.06
9.07
9.08
9.09
9.10
9.11
9.12
9.13
9.13
35.0
7.65
7.67
7.67
7.68
7.69
7.70
7.71
7.72
7.73
7.73
7.74
40.0
6.62
6.63
6.64
6.65
6.65
6.66
6.67
6.67
6.68
6.69
6.69
45.0
5.82
5.83
5.84
5.84
5.85
5.86
5.86
5.87
5.87
5.88
5.88
50.0
5.18
5.19
5.20
5.20
5.21
5.21
5.22
5.22
5,23
5.23
5.23
55.0
4.66
4.67
4.67
4.68
4.68
4.69
4.69
4.70
4,70
4.70
4.71
60.0
4.23
4.24
4.24
4.25
4.25
4.25
4.26
4.26
4.27
4.27
4.27
65.0
3.87
3.87
3.88
3.88
3,89
3.89
3.89
3.90
3.90 i
3.90
3.90
70,0
3.56
3,56
3,57
3.57
3,57
3.58
3.58
3.58
3,59
3,59
3.59
75.0
3,29
3.30
3.30
3.30
3.31
3.31
3.31
3,31
3.32
3.32
3.32
Table 5 Theoretical Rankine coefficients of performance (COP)t for a range of lihs and condensing temperatures for R22
T~'~ba:
r
45,0
(TCO.T~,)~,,~ ] 17.341
46.0
47.0
48.0
49.0
50.0
51.0
52.0
$3.0
54.0
53.0
17.757
18.182
18.614
19.033
19.500
19.954
20.416
20.886
21.364
21.851
10.0
28.84
28.86
28.87
28.88
28.92
28.94
28.92
28.94
28.95
28.96
28.95
15.0
18.97
18.98
18.99
19.01
19002
19.03
19.03
19004
19.04
19.04
19.04
20.0
14.04
14.05
14.06
14.07
14.08
16.08
14.09
14.09
14.09
14.09
14.09
25.0
II.I0
11.10
11.11
11.12
II.12
11.13
II.13
11.13
11.13
11.13
11.12
30.0
9.13
9.14
%14
9.15
9.15
9.16
9.16
9.16
9.16
9.16
9.16
35.0
7.74
7.74
7.74
7.75
7.75
7.75
7.76
7.76
7.76
7.76
7.75
40.0
6.6Y
6.69
6.70
6.70
6,70
6.71
6.71
6.71
6.71
6.71
6,70
45.0
5.88
5.88
5.89
5.89
5.89
5.89
5.89
5,89
5.89
5.89
5.89
50.0
5.23
5.24
5.24
3.24
5.24
5.24
5.25
5.25
5.25
5.24
3.24
55.0
4.71
4.71
4.71
4.71
6.72
4.72
6.72
4.72
4.72
4.72
4.71
60.0
4.27
4.27
4.2~
4.28
4.28
4.28
4.28
4.28
4.28
4.28
6.28
65.0
3.90
3.91
3.91
3.91
3.91
3.91
3.91
3.91
3.91
3.91
3.91
70.0
3.59
3,59
3.59
3.60
3.60
3,60
3.60
3.60
3.60
3.60
3.59
75.0
3.32
3.32
3.32
3.32
3.33
3.33
3,33
3,33
3.33
3.32
3.32
Thermodynamic data for heat pump systems operating on R 2 2
115
Table 6. Theoretical Rankine coefficients of performance (COPh for a range of lifts and condensing temperatures for R 2 2
55.0
(Tco~rv)oc~ 2t.8st
56.0
57o0
58.0
59.0
60.0
61.0
62.0
63.0
64.0
63.0
22.346
22.848
23.359
23.879
26.6o7
26.963
25.688
26.o63
26.6o6
27.178
1
10.0
28.93
28.93
28.94
28.91
28.86
28.84
28.86
28.82
28.75
28.71
28.65
15.0
19.04
19.02
19.02
19.00
18.98
18.98
18.96
18.95
18.91
18.88
18.84
20.0
14.09
16.08
14.08
14.06
14.05
14.06
14.03
14.02
13.99
13.97
13.94
25.0
11.12
11.12
11.]2
11.11
11.10
11.09
11.08
11.07
11.03
11.03
11.01
30.0
9.16
9.15
9.15
9.14
9.13
9.12
9.12
9.11
9.09
9.0e
9.06
35.0
7.75
7.75
7.75
7.76
7.73
7.73
7.72
7.71
7.70
7.69
7.67
40.0
6.70
6.70
6.70
6.69
6.69
6.68
6.68
6.67
6.66
6.65
6.63
63.o
5.u9
5.89
5.89
3.88
5.88
5.87
5.86
5.86
5.85
5.84
5.83
50.0
5.24
S.2t
5.26
5.23
5.23
3.23
5.22
5.21
5.21
5.20
5.19
33.0
6.71
4.71
6.71
4.71
4.70
4.70
6.69
4.69
4.68
4.67
4.67
60.0
6.28
4.27
4.27
4.27
6.27
6.26
6.26
4.25
4.25
&.24
4.23
65.0
3.91
3.91
3.90
3.90
3.90
3.89
3.89
3.89
3.88
3.87
3.87
70.0
3.59
3.59
3.59
3.39
3.58
3.58
3.58
3.57
3.57
3.56
3.56
73.0
3.32
3.32
3.32
3.32
3.31
3.31
3.31
3.30
3.30
3.29
3.29
Table 7 Theoretical Rankine coe~cients of performance (COPh for a range of lifts and condensing temperatures for R22 ,
!
65.0
66.0
67.0
68.0
69.0
70.0
71.0
27.178
27.758
28.349
28.968
29.558
30.177
30.803
72.0
73,0
31.440: 32.089
74.0
J 73.0 I
32.746 133.412
10.0
28.65
28.63
28.54
28.49
28.43
28.24
28.21
28.16
27.93
27.8~
27.81
IS.O
18.84
18.82
1~.77
18.72
18.66
18.58
18.35
18.51
18.39
18.33
18.27
20.0
13.94
13.92
13.89
13.86
13.73
13.69
13.61
13.55
13.51
25.0
11.01
10.99
10.97
10.94
1 3 . 8 1 1 13.75 i 10.91 10.87
10.84
10.81
10.75
10.71
10.67
30.0
9.06
9.05
9.02
9.00
8.98
8.94
8.92
8.90
8.85
8.81
8.78
35.0
7.67
7066
7064
7.62
7.60
7.57
7.55
7.33
7.50
7.47
7.44
40.0
6063
6.62
6.61
6.59
6.57
6.55
6.33
6.51
6.48
6.46 I
6.43
43.0
5.83
5.82
3.80
5.79
3.78
3.76
5.76
3.72
3.70 i
5.67
I
5.65
30.0
5.19
5.18
5.17
S. lS
5.14
5.12
5.11
S.09
5.07
5.05
35.0
6.67
4.66
6.65
6.64
6.62
6.61
4.60
4.58
&.56
4.54
4.53
60.0
4.23
6.22
6.22
6.21
6.19
4.18
6.17
6.16
4.14
4.12
6.11
65.0
3.87
3.86
3.85
3.84
3.83
3.82
3.81
3.~0
3.78
3.77
3.75
5.03
70.0
3.56
3.55
3o5&
3.53
3.52
3.51
3.50
3.69
3.48
3.47
3.45
75.0
3.29
3028
3.28
3.27
3.26
3.25
3.24
3.23
3.22
3.21
3.19
116
R ZYLLA et . I
Table 8 Theoretical Rankine coefficients of performance ICOPh for a range of lifts and condensing tempera tures for R22
75.0 ~co.TEv)oC ~ar)
76.0
II
77.0
78.0
79.0
80.0
81.0
83.0
38.370 139"122
84.0
83.0
34.090134.779i
35.476
10.0
27.81
27,51 i 27.34
27.10
27.00
26.94
26.24
25.59
18,27
18.12 I 17,99 I 17,87
17.77
17.68
17.36
26.07 i 17.40 i 17.16
25.91
15.0
17.05
16.92
20.0
13.51
13.42
13.24
13.18
13.09
12.90
12.88
12.73
12.63
12.52
25.0
10.67
10,60 i 10.54 ! 10,67
10.19 ! 10.07
30.0
8,7~
8.73
8.68
35.0
7.44
7.39 !
40.0
6.43
45.0
5.65
50.0
5.03
13.33
36.183 ....... 36.902!37.633
82.0
35.412
26.37!
39.883 4 0 . 6 5 5
10.41
10034
10.22
10.00
9.90
8.62
8.57
8.52
8.62
8.39 I:
8.3O
8.23
8.15
7.35
7.30
7.26
7.22
7.14
7.11 /
7,04
6.98
6.9t
6,40 :
6.36
6,32
6.28
6.24
6,18
6.15 i
6.09
6.04
5.99
5.62 :
5.59
5.56
5.53
5.49
5.44
5.41
5.36
5.32
5.27
5.00
4.98
4.95
4.92
4.89
4.85
4.82
4.78
4.74
4.69
t
:
I
55.0
4.53
4.50 ! 4.48
4.45
4.43
4.40
4.36
4.34
4.30
4.27
4.23
60.0
4,11
4.09
4,06
6.04
6.02
3.99
3.96
3.94
3.91
3,87
3.84
65.U
3.75
3.74
3,72
3.70
3.67
3.65
3.62
3.60
3.57
3.54
3.51
70.0
3.45
3.44
3.42
3.40
3.38
3.36
3.34
3.32
3.29
3.26
3.23
75.0
3,19
3.18
3.16
3.15
3.13
3.11
3,09
3.07
3,04
3.02
2.99
Table 9. Compression ratios Pco/PEvfor a range of liRs and condensing temperatures for R22
(TC~O.5,Ev)or~r )
--%
15.0
16.0
7,877
8.109
17.0
18.0
19.0
20.0
21.0
2200
23.0
2400
8.346
8.588
80835
g.087
9.346
9.60tI
9 . 8 7 8 J 10.152
25.0 10.632
i
10.0
1.353
1.350
1.347
1.344
1.341
10338
1.335
1.333
1.330
1.327
1.324
15.0
1.587
1.582
1.5761
1.571
10566
1.561
1.556
1.551
1.546
1,541
1.536
20.0
1.874
1.865
1.857
1.868
1.84~
1.831
1.823
1.815
1.807
1.799
1.792
25.0
2.229
2.215
2.201
2,188
2,175
2.162
2.150
2.138
2.126
2.114
2.102
30.0
2.669 I 2.669
2.629
2.609
2,590
20571
2.553
2.535
2.517
20500
20482
35.0
3,222
30163
3.135
3.107
30080
3,0$3
30027
3.001
2.976
2.952
3.193
60.0
3.923
3.880
3.838
3.797
3.757
3.718
3.680
3.662
3.606
3.570
30535
45.0
4.819
6.757
4.697
4.638
4.581
6.526
40472
60419
4.367
4.317
4.268
50.0
5.976
5.888
5.803
5.719
5.638
50559
5.483
5.408
5.335
5.26~,
5.195
55.0
7.490
7.364
70241
7.122
7.007
6.895
6.787
6.681
8.578
6.479
6.382
60.0
9.493
9.311
9.136
8.965
8.801
80641
8.487
8.338
8.192
8.052
7.915
65.0
12.177
11.915
11.661
110416
11.180
10.952
10.732
10.519
10.312
10.113
9.920
70.0"
15.825 1 5 . 4 6 3
15.074
14.719
16.378
14.049
13.732
13.427
13.131
12.847
12.573
75.0
20.858
19.754
19.234
18.737
18.257
17.798
17.356
16.930
16.522
16.128
200294
Thermodynamic data for heat pump systems operating on R22
117
Table 10 Compression ratios Pco/PEvfor a range of lifts and condensing temperatures for R22
25o0 10.432
26.0
27.0
10.718 !11.010
28.0
2900
30.0
31.0
32.0
3300
3400
35.0
11.307
11.611
11.920
12.236
12.558
12.886
13.220
13.561
10.0
1.324
1.322
1.319
1.317
1.314
1.312
1.309
1.307
1.305
1.302
1.300
15.0
1.536
1.531
1.527
1.522
1.518
1.513
1.509
1.505
1.501
1.496
1.492
20.0
1.792
1.784
1.777
1.769
1.762
1.755
1.748
1.761
1.735
1.728
1.722
25.0
2.102
2.091
2.080
2.037
2.027
2.016
2.007
1.997
2,482
2,466
2,449
2.069 I 2.058 I 2,433 2,418
2.047
30,0
2,402
2,387
2,372
2,357
2,343
2,329
35,0
2,952
2,928
2,904
2,881
2,t;59
2,837
2,815
2,79/*
2,773
2,753
2,733
40,0
3,535
3,501
3,468
3,436 I 3,404
3,373
3,342
3,313
3,283
3,255
3,227
45.0
4.268
4.220
4.173
I 4.128 ! 4.083
4.040
3.997
3.956
3.915
3.876
3.837
50.0
5.195
5.128
5.063
4.999
4.937
4.877
4.818
4.760
4.704
4.649
4.596
55.0
6.382
6.288
6,196
6.107
6.021
5.937
5,855
5.775
5,697
5,622
5.548
60,0.
7,915
7,783
7,655
7,530
7,410
7,292
7,178
7,068
6,960
6,855
6,754
65,0
9,920
9,734
9,553
9,378
9,209
9,045
8,886
8,731
8,582
8,437
8,296
70.0
12.573
12.3041
12.052
11.805
11.566 1 1 . 3 3 5
11.112
10.896
10.687
10.485
10.290
75.0
16.128
15.749
15.386
15.032
14.693
14.051
13.747
13.453
13.170
12.896
14.366
Table 11. Compression ratios Pco/P~v for a range of lifts and condensing temperatures for R22
t0.0
35.U
36.0
37.0
38.0
39.0
40.0
13.561
13.909
14.263
14.624
14.991
15.365
1.300
1.298
1.295
1.293
1.291
1.289
41.0
42.0
15.746!16,136 1.287
1.285
43.0
44.0
45.0
16,529
16.932
17.341
1.283
1.281
1.279
15.0
1.692
1.488
1.484
1.481
1.477
1.473
1.469
1.465
1.462
1.458
1.455
20.0
1.722
1.715
1.709
1.703
1.697
1.691
i.685
1.679
1.673
1.668
1.662
25.0
t.997
1.987
1.978
1.969
1.933
1.925
1.916
1.908
I 1.96U I 1.~51
1.942
30,0
2,329
2,315
2,302
2,28W
2,275
2,262
2,250
2,237
2,225
2,213
2,202
35,0
2,733
2,713
2,694
2,675
2,657
2,639
2,621
2,604
2,586
2,570
2,553
40.0
3.227
3.200
3.173
3.147
3.121
3.096
3.072
3.047
3.024
3.001
2.978
45.0
3.837
3.799
3.762
3.726
3.691
3.656
3.622
3.589
3.557
3.525
3.494
50.0
4.596
4.544
4.493
4.443
4.395
4.347
~.301
4.256
4.212
4.169
4.126
$$.0
5.548
5.476
50406
5.338
50272
5.207
5.144
5.082
5.022
4.964
4.906
60.0
6.754
6.455
6.559
6.466
6.374
6.286
6.200
6.116
6.034
5.954
5.877
65.0
8.296
8.160
8.027
7.899
7.773
7.652
7.534
7.419
7.308
7.200
7.094
70.0
10.290
10.100
9.917
9.739
9.567
9.400
9.237
9.080
8.928
8.780
8.636
75.0
1~.896
12.631
12.376
12.129
11.889
11.658
11.434
11.218
11.008
10,805
100608
H.X.S.! 2---C"
R. ZYLLA et al.
118
T a b l e 1 2 C o m p r e s s i o n r a t i o s Pco/PEv for a r a n g e o f liRs a n d c o n d e n s i n g t e m p e r a t u r e s for R22 ~ , ~ c o °C ~co(Pco
45.0
46.0
47.0
48.0
49.0
50.0
51.0
52.0
53.0
54.0
55.0
17.341
17.757
18.182
18.614
19.053
19.500
19.954
20.416
20.886
21.364
21.851
10.0
1.279
1.277
1.275
1.273
1,271
1.269
1.267
1,265
1.264
1.262
1.260
15.0
1.455
1.451
1.448 [ 1.444
1.441
1.438
1.435
1.431
1.428
1.425
1.422
20.0
1.662
1.657
1.6511
1.646
1.641
1.636
1.631
1.626
1.621
1.616
1.611
25.0
1.908
1.900
1.892 I 1.884
1.~77
1.869
1.862
1.854
1.847
1.840
1.833
30.0
2.202
2.190
2.1791
2.108
2.157
2.146
2,135
2.125
2,114
2.104
2.095
(Tco~Oc~ "
1
q
i 35.0
2.553
2.537
2.521 i
2.506
2.491
2.476
2.461
2.4461
2.432
2.418
2.405
40.0
2.978
2.956
2.934 i 2.913
2,892
2.871
2.851
2.831
2.812
2.793
2.774
45.0
3.494
3.464
3.434
3.377
3.349
3.322
3.295
3.268
3.243
3.217
3.405
50.0
4.126
4.085
4.045 i 4.006
3.967
3.929
3.893
3.856
3.821
3.786
3.753
55.0
4.906
4.851
4.796
4.743
4.691
4.640
4.591
4.542
4.495
4.448
4.403
60.0
5.877
5.801
5.727
5.656
5,585
5.517
5.451
5.386
5.322
5.260
5.200
65.~
7.094
6.992
6.892
6.795
6.700
6.608
6.519
6.431
6.346
6.263
6.182
I
70.0
8.636
8.496
8.361
8.230
8,102
7.977
7.857
7,739
7,624
7.513
7.405
75.0
10.608
10.417
10.233
10.054
9.880
9.711
9.548
9.389
9.234
9.085
8.939
T a b l e 13. C o m p r e s s i o n r a t i o s Pco/PEv for a r a n g e o f lifts a n d c o n d e n s i n g t e m p e r a t u r e s for R 2 2
'"°
"'°
'"°
"'°
,.o
,o.o
,,.o
,.o
i
,,.o
21,851
22.346
22.848
23.159
23.879
24.407
24.943
25°488
26.043
26.606
27,178
10.0
1.260
1.258
1.237
1.255
1.253
1.252
1.230
1.248
1.247
1.245
1.244
15.0
1.422 I
1.419
1.416
1.413
1.410
1.408
1.405
1.402
1.399
1.396
1.394
20.0
1.611
1.607
1.602
1.597
1.593
1.588
1.584
1.580
1.576
1.571
1.567
25.0
1.833
1.826
1.819
1.813
1.806
1.800
1.793
1.787
1.781
1.775
1.769
30.0
2.095
2.085
2.075
2.066
2.057
2.0/*8
2.038
2.Q30
2.021
2.012
2.004
35.0
2.405
2.391
2.378
2.365
2.352
2.340
2.327
2.313
2.303
2.291
2280
40.0
2.774
2.756
2.7)8
2.720
2.703
2.686
2.669
2.653
2.637
2.621
2.605
45.0
3.217
3.193
3.188
.3.145
3.121
.3.099
3.076
3.054
.3.033
3.011
2.991
50.0
3.753
3.720
3.687
3.655
3.624
.3.594
3.564
3.535
3.506
3.478
3.450
55.0
4.403
4.359
4.316
4.273
4.232
4.192
4.152
4.113
4.075
4.038
4.002
60.0
5.200
5.141
5.083
5.027
4.972
4,918
4.866
4.814
4.764
4.715
4.667
65.0
6.182
6.104
6.027
5.952
5.879
5.808
5.7)8
5.670
5.604
5.540
5,477
70.0
7.405
7.300
7.197
7.097
7.000
6.906
6.813
6.723
6.636
6.551
6.467
75.0
8.939
8.798
8.661
8.527
8.398
8.271
8.148
8.029
7.913
7.800
7.690
Thermodynamic data for heat pump systems operating on R22 i
Table 14 Compression ratios
! 19
!
Pco/PEv for a range of lifts and condensing temperatures for R22
65.0
66.0
67.0
68.0
69.0
70.0
71.0
72.0
73.0
74.0
73,0
27.178
27.758
28.349
28.948
29.558
30.177
30.803
31.460
32.089
32.746
33.412
10.0
1.244
1.242
1.241
1.239
1.238
1.236
1.235
1.234
1.232
1.231
1.229
15.0
1.394
1.391
1.389
1.386
1.384
1.381
1.378
1.376
1.374
1.371
1.369
20.U
1.567
1.563
1.559
1.555
1.551
1.548
1.544
1.540
1.336
1.533
1.529
25.0
1.769
1.763
1.757
1.751
1.746
1.740
h735
1.729
1.724
1.719
1.713
30.0
2.0(~
1.996
1.988
1.980
1.972
1.964
1.936
1.949
1.941
1.934
1.927
35.0
2.280
2.269
2.257
2.246
2.236
2.225
2.215
2.204
2.194
2.184
2.175
40.0
2.605
2.590
2.575
2,560
2.546
2.532
2.517
2,506
2.490
2,47P
2.664
45.0
2.991
2.970
2.950
2.931
2.911
2.893
2.874
2.856
2.838
2.820
2.803
50.0
3.450
3,423
3.397
3.371
3.346
3.321
3.296
3.272
3.269
3.225
3.203
55,0
4.002
3.966
3.931
3.897
3.864
3.831
3.799
3.767
3,737
3.706
3.677
60.0
4.667
4.621
4.575
4.530
4.486
4.443
4.401
4,360
4.320
4.280
4.242
65.0
5,477
5.415
5.355
5.296
5.238
5,183
5,127
$,074
5,021
4.970
4.920
70.0
6.467
6.386
6.307
6.230
6.154
6.081
6.009
5.939
5.870
5.803
5.738
7 5.0
7,690
7.582
7,478
7,376
7.277
7.181
7.086
6.994
6.906
6.818
6.733
Table 15 Compression ratios
Pco/P~v for a range of liRs and condensing temperatures for R22
., o0
-<
(TCO-TI[V)
75.0
76.0
77.0
7B.0
79.0
80.0
81.0
82.0
83.0
84,0
85.0
33.412
34.090
34.779
35.476
36.183
36.902
37.633
38.370
39.122
39.883
40.655
10.0
1.229
1.228
1.227
1.226
1.224
1.223
1.222
1.220
1.219
1.218
1.217
15.0
1.369
1.367
1.365
1.362
1.360
1.358
1.356
1.353
1.351
1.349
1.347
20.0
1,529
1.526
1.522
1.519
1.515
1.512
1.509
1.505
1.502
1.499
1.496
25.0
1.713
1.708
1.703 : 1.699 i
1.694
1.689
1.684
1.679
1.675
1.670
1.666
30.0
1.927
1.920
1.913!
1.906
1.899
1.892
1.886
1.879
1.873
1.867
1.861
2.146
2.137
2.128
2.119
2.110
2.102
2.093
2.085
I
I
35.0
2.175
2.165
2.156
40.0 45.0
2.464
2.451
2.438 i 2.426
2.414
2.402
2.390
2.378
2.367
2.356
2.344
2.803
2.786
2.770 , 2.753
2.737
2.721
2.706
2.690
2.675
2.661
2.646
50,0
3.203
3.1~1
3,159 : 3.137
3,116
3.096
3.076
3.055
3.036
3.017
2.998
t
55.0
3,677
3.648
3.619
3.592
3,564
3.537
3.511
3.485
3,460
3.435
3.411
60.0
• 4.242
4.204
4.167
4.131
4.095
4.061
4.027
3.993
3.961
3.928
3.897
65.0
4.920
4.871
4.823
4.776
4.730
4.685
4.641
4.$98
4.556
4.514
4.474
70.0
5.738
5.674
5.612
5.551
5.492
5.434
5.377
5.321
5.267
5.213
5.161
75.0
6.733
6.650
6.569
6.490
6.413
6.337
6.266
6.192
6.122
6.053
5.986
120
R. ZYLLA e t U/.
Since the compression from point $2 to point D1 is isentropic, ~s2 = (~)Ol where ~ is the entropy per unit mass. For design purposes, the enthalpy per unit mass of the superheated vapour at D1 can be approximately related to the enthalpy per unit mass of the saturated vapour at point D2 by the equation HD, = HD2 + (¢)s2 - @D2)Tco.
(2)
Equations (1) and (2) can be used to calculate (COPh values for any desired condensing temperature Tea and temperature lift (Tea - TEv) from the saturated properties of the chosen working fluid. Here, the theoretical Rankine coefficient of performance (COPh and the compression ratio Pco/PEv have been calculated for R22 for temperature lifts of 10-75°C in 5°C increments and condensing temperatures Tea for every degree in the range of 15-85°C. The basic thermodynamic properties of R22 used in the calculations have been taken from 'Thermodynamic Properties of Arcton 22 SI units' published by Imperial Chemical Industries Limited, Imperial Chemical House, Millbank, London SWlP 3JF. Tables 2-8 list the calculated (COPh values and Tables 9-15 the calculated Pea/PEr values. Figures 2-7 are plotted from the data listed in the tables. DISCUSSION OF DERIVED DATA
In Fig. 3, the compression ratio Pco/PEv and theoretical Rankine coefficient of performance (COPh are plotted against the temperature lift (Tco - TEv) for a condensing
20
5. TC 0 =6 0 " C
--19
18 = 4
. 7 bar
.~E o -- 15 _
-
e==
,=_o
.
~
-t4
..~ a.
-,3
8
--t2
a.w
o 3.0 0..o
-- ~0
.8_
- 8
oE
-6
,-, o
._e
2.0 --
==
-- 5
--2
I
.
C
20 ~
30 (
~4 0
) 50
O
60
I,-
0
Temperature lift (Tea- TEv), °C
t
0
1
10
I
20
I
30
1
40
I
50
Temperature lift (TD - T s ) , =C wilt) 20=C drop in heat exchangers
Fig. 3. Compression ratio and theoretical Rankine coefficient of performance against temperature lift for R22 at a condensing temperature of 60°C and a condensing pressure of 24.407 bar.
Thermodynamic data for heat pump systems operating on R22 20
121 2O
19 18
Condensing m ~ u r e
17
T~.,5-c
,6
15 Tco'85"C
_
~.
15 'i 1 4 . "o -
.E
,3 -~ O.
.!
°
~
%.,5.c
,~ ~
-
II
i
lO ,~
I0
9 "6
,I 0
to
2o
3o
4o
50
60
7o
Temperature lift (Tco-TEv) , "C Fig. 4. Variation of compression ratio and theoretical Rankine coefficient of performance with temperature lift and condensing temperature for R22.
(TCO-TEV)"20°C
13 l_ 12
/(Tco- TEO, 25"(:
II
I09
"/" ~ c
o"'rEv )" 3o-c
8
15"C
7
~L. . . . .
--~-
TEV)" 40"C
5-4 3
Condensing tempsrolure
2-
T:o. es'c
'-
c
I
2
I
3
I
4
l
5
I
6
I
7
Compression rotio Pco/PEv, dims~oNess
Fig. 5. Th~retical Rankine e~fl~eient of perfonmance against compression ratio showing the influence of temperature lift and condensing temperature for R22.
122
R. ZYLLA el (//.
~5 Temperature lift ( T 0- T v) =2OoC
13-
~
12
-
E ~5
(TCO- TEv) " 25=C
(T=-
._~
7 -
(Tr_x)-TEJ- 40"C
5
(Tco-TEv)= 4---
315
Z~
30 4~ 5~ 6~ Condensing temperature Tco, °C
7k
Fig. 6. Theoretical Rankine coefficient of performance against condensing temperature for various temperature lifts for R22.
temperature 60°C. The effective temperature lift will be reduced by 20°C for a temperature drop of 10°C in each of the heat exchangers. Figure 4 shows that Pco/PEv values for a given temperature lift ( T c o - TEv) are extremely sensitive to the condensing temperature Tco. In contrast, the (COP)R values are almost independent of the condensing temperature. Figure 4 highlights the necessity for heat pump systems to be carefully matched in a specific application. This is further illustrated by Fig. 5, which is a plot of (COP~ against Pco/PEv for various temperature lifts ( T c o - TEv). Figure 5 implies that relatively high coefficients of performance are only possible for relatively low t©mperature lifts and compression ratios. The heating of buildings and the operation of fractional distillation columns are amongst the potential applications for such systems. The sensitivities of (COPk and Pco/P~v to the condensing temperature Tco at various temperature lifts (T¢o - TEv) are illustrated in Figs 6 and 7 respectively. Figure 6 shows that the theoretical Rankine coefficient of performance (COP)= increases almost linearly with the condensing temperature for all temperature lifts and then decreases after reaching maxima in the region of T¢o = 50°C. The maximum is more pronounced for lower temperature lifts. Figure 7 shows the variation of compression ratio with condensing temperature for various temperature lifts.
Thermodynamic data for heat pump systems operating on R22
123
t 17
16 15 .-
Temperature Iif!
•6
i2--
:> 0,,.w
If --
0-8 o
I0--
~
9
._~
U
15
25
:55
I
45
I
55
I
65
I
75
i
85
Condensing temperolure Tco, "C
Fig. 7. Compression ratio against condensing temperature for various temperature lifts for R22.
NOMENCLATURE
(COP)x Hx /'co PEV Tco TD TEV Ts W 0x
Rankine coefficient of performance of a heat pump system [dimensionless] Enthalpy per unit mass at state condition X [kJ kg - t ] Pressure in the condenser of a heat pump system [bar] Pressure in the evaporator of a heat pump system [bar] Temperature of the working fluid in the condenser ['K or °C] Temperature of the heat sink fluid from the heat pump system [K or °C] Temperature of the working fluid in the evaporator [K or °C] Temperature of the heat source fluid to the heat pump system [-K or °C] Work rate to the compressor of a heat pump system [kW] Entropy per unit mass at state condition X [-kJ kg- ~ K - 1]
DERIVED
0198/7593/81/020111-13502,00/0 Pergamon Press Led
THERMODYNAMIC DATA FOR HEAT SYSTEMS OPERATING O N R22
PUMP
K. W. TAI, S. DEVOTTA, F. A. WATSON and F. A. HOLLAND Department of Chemical Engineering, University of Salforcl, Salford M5 4WT, U.K. R. Z Y L L / ~
Abstract--The theoretical Rankine coefficients of performance (COP~ and the compression ratios have been presented for heat pump systems operating on R22. These values are listed in tabular form for temperature lifts of 10--75°C in 5°C increments and condensing temperatures Tea for every degree in the range of 15-85°C. Several graphs have been drawn to illustrate the feasible operating range for R22 heat pump systems. The derived thermodynamic data can be used for the rapid preliminary design of heat pump systems operating on R22.
INTRODUCTION
A VAPOUR compression heat pump, diagrammatically shown in Fig. 1, consists of two heat exchangers, a compressor and an expansion valve. The operation of the system is based on the continuous recycling of the working fluid. The working fluid vapourises in the evaporator heat exchanger at a temperature TEe by extracting heat from a heat source and, after compression, releases its latent heat in the condenser heat exchanger at a temperature Tco to a heat sink. The condensing temperature Tco, the temperature lift (Tco - TEe) and the compression ratio Pco/PEv, which is the ratio of the corresponding pressures in the condenser and evaporator are the critical parameters which determine the feasible operating range of a heat pump with a particular working fluid. R22 is one of the more widely used working fluids, both in refrigeration and heat pump systems. Its chemical formula is CHCIF2 and its critical temperature and pressure are 369.1 K and 49.921 bar respectively. Physical data for R22 are listed in Table 1. The principal disadvantage with R22 is the relatively high condensing pressures Pep which correspond to relatively modest condensation temperatures Tco.
drop
~elivered heat
t
Comoressor
Exponsior~
temperature
vo,.
,,,,.,0_,,
HeOJ' source m
~' __]__~EX _ _ _
t
I
Fig. 1. Simplified diagram of a vapour compression heat pump.
lil
112
R. ZYLLA et al. Table 1. Physical data for R22
TCO
PCO
density kg m -3
PV
latent heat
bar m 3 kg -] oC
bar
liquid
vapour
kJ kg -I
O
4.96256
1285.7
21.1018
0.23517
205.991
5
5.82289
1268.5
24.6544
0.23618
202.029
I0
6.79153
1250.8
28.6757
0.23683
15
7.87684
1232.6
33.2172
20
9.08749
1213.8
25
10.43233
1194.4
30
11.92061
1174.2
35
13 56165
40 45
MJ m -3
vapouz 4.3467
enthalpy of saturated vap°uxl
kJ k a - "
mass of working fluid kg MJ -I
305.991
4.8546
4.9809
307.822
4.9497
197.888
5.6745
309.552
5.0534
0.23713
193.557
6.4294
311.171
5.1664
38.3380
0.23703
189.016
7.2464
312.670
5.2906
44.1055
0.23653
184.247
8.1263
314.039
5.4275
50.5987
0.23559
179.225
9.0685
315.264
5.5796
1153.3
57.9099
0.23418
173.923
10.0718
316.332
5.7497
15.3651
1131.51
66.149
0.23228
168.305
11.1320
317.226
5.9422
17.3409
1108.68
75.453
0.22982
162.327
12.2480
317.926
6.1604
50
19.4994
1084.66
85.989
0.22676
155.934
13.4086
318.406
6.4129
55
21.8510
1059.24
97.973
0.22303
149.054
14.6032
318.631
6.7090
60
24.4068
1032.12
111.695
0.21851
141.588
15.8146
318.556
7.0627
65
27.1779
1002.91
127.555
0.21306
133.399
17.0157
318.113
7.4963
70
30.1759
971.O3
146.149
0.20647
124.284
18.1639
317.201
8.O461 8.7779
75
33.413
935.58
168.434
0.19837
113.922
19.1883
315.652
80
36.902
895.03
196.018
0.18825
101.836
19.9616
313.187
9.8197
85
40.~55
846.39
231.705
0.17546
87.336
20.2361
309.360
11.4500
90
44.686
782.10
283.041
0.15787
68.362
19.3492
302.981
14.6280
95
49.O10
661.17
391.O21
0.12533
34.425
13.4608
288.129
29.0488
49.921
524.79
524.790
0.09513
0.000
0.0OOO
270.470
96.01 CRITICAl
DERIVED THERMODYNAMIC DATA The operation of a conventional vapour compression heat pump i~ based on the Rankine cycle. The ideal Rankine cycle is illustrated in Fig. 2 which is a plot of pressure P against enthalpy per unit mass H for R22. With reference to Fig. 2, the theoretical Rankine coefficient of performance of a heat pump can be defined as (COP). - HD1 -- Hv3 Hol - Hs2'
(I)
~00--
4 0 O -30.0
DI
200 150 -~ 0-"
I00
~
70
~ O.
5.() 3.0 20: 15 ~0'
40
60 80
O0 ~20 ~40 60 80 2 0 0 Z 2 0 Z 4 0 Z S O ~ 3 0 0 3 2 0 Enff~lpy per unit moss H, kJ kg-I
Fig. 2. Pressure against enthalpy per unit mass for R22.
340
Thermodynamic data for heat pump systems operating on R22
II3
Table 2. Theoretical Rankine coemcients of performance ( C O P k for a range of liftsand condensing temperatures for R22
~
(b.:)
15.0
16.0
17.0
16.0
19.o
20.0
21.0
22.0
23.0
24.0
25.u
(TCO-'L'I~, ~
7.877
8o109
8.346
8.588
8.835
9.087
Y.346
9.609
9.878
10.152
10.432
lO.O
27.34
27,42
27.49
27.55
27.61
27.67
27,74
27.81
27.85
27.91
27.98
15.0
18.00
18.05
18.10
18.14
16.18
18.22
18.26
18.31
18.34
18.38
18.42
2U.O
13.34
13.38
13.41
13.44
13.47
13.50
13.53
25.0
10.55
10.58
10.60
I0.63
10.65
10.67
10.70
13.56
13.59
13.62
13.6$
10.72
10.74
lO.7b
10.79
30.o
8.69
8.71
8.73
8.75
8.77
8.79
8.81
e.83
s.e$
8.87
s.e8
35.0
7.37
7.39
7.40
7.42
7.44
7.45
7.47
7.48
7.50
7.S!
7.~3
40.0
6.38
6.39
6.41
6.42
6.44
6.45
6.46
6.48
6.49
6.50
6.51
1*5.0
5.61
5.62
5.64
5.65
5.66
5.67
5.68
5.7U
5.71
5.72
5.73
50.0
5.00
5.01
5.02
5.03
5.04
.5.0$
5.06
5.07
5.08
5.09
s. 10
.55.0
4..50
4.51
4..52
4..53
4°.54
4.5.5
4..56
4..57
4.57
4.S~
4..59
60.0
4.09
4.10
4.11
4.11
4.12
4.13
4.14
4.15
4.1.5
4.16
4.17
6.5.0
3.74
3.75
3.76
3.76
3.77
3.78
3.78
3.79
3.80
3.81
3.81
70.0 ,
3.44
3.4.5
3.46
3.46
3,47
3.48
3.48
3.49
3.50
3.50
3.51
73.0
3.19
3.19
3.20
3,21
3.21
3.22
3.22
3.23
3.24
3.24
3.25
Table 3. Theoretical Rankine coefficients of .performance (COPk for a range of lifts and condensing temperatures for R22
R Z Y L L A el' O•.
114
Table 4 Theoretical Rankine coefficients of performance (COP)R for a range of lifts and condensing temperatures for R22 ~ e o °e
! 35.0
36.0
37.0
13.561
13.909
14.263
1o.0
28.4,
2,.53
28.57
28.63
fT -,r ~ ; r ) c%-T~)oc'~
38.0
39.0
40.0
14.624 14.991 15.365
28.65
28.68
41.0
42.0
43.0
44.0
15.746
16.134
16.529
16.932
28.73
28.76
28.80
28.81
~ 45.0 !
17.341 28.84
15.o
18.75
18.78
18.8o
18.84
18.86
18.87
18.9o
18.92
18.94
18.96
18.97
20.0
13.89
13.91
13.92
13.95
13.96
13.98
14.00
14.01
14.03
14.04
14.04
25.0
10.97
10.99
11.00
11.02
11.03
11.04
11.06
11.07
11.08
11.09
11.10
30.0
9.04
9.05
9.06
9.07
9.08
9.09
9.10
9.11
9.12
9.13
9.13
35.0
7.65
7.67
7.67
7.68
7.69
7.70
7.71
7.72
7.73
7.73
7.74
40.0
6.62
6.63
6.64
6.65
6.65
6.66
6.67
6.67
6.68
6.69
6.69
45.0
5.82
5.83
5.84
5.84
5.85
5.86
5.86
5.87
5.87
5.88
5.88
50.0
5.18
5.19
5.20
5.20
5.21
5.21
5.22
5.22
5,23
5.23
5.23
55.0
4.66
4.67
4.67
4.68
4.68
4.69
4.69
4.70
4,70
4.70
4.71
60.0
4.23
4.24
4.24
4.25
4.25
4.25
4.26
4.26
4.27
4.27
4.27
65.0
3.87
3.87
3.88
3.88
3,89
3.89
3.89
3.90
3.90 i
3.90
3.90
70,0
3.56
3,56
3,57
3.57
3,57
3.58
3.58
3.58
3,59
3,59
3.59
75.0
3,29
3.30
3.30
3.30
3.31
3.31
3.31
3,31
3.32
3.32
3.32
Table 5 Theoretical Rankine coefficients of performance (COP)t for a range of lihs and condensing temperatures for R22
T~'~ba:
r
45,0
(TCO.T~,)~,,~ ] 17.341
46.0
47.0
48.0
49.0
50.0
51.0
52.0
$3.0
54.0
53.0
17.757
18.182
18.614
19.033
19.500
19.954
20.416
20.886
21.364
21.851
10.0
28.84
28.86
28.87
28.88
28.92
28.94
28.92
28.94
28.95
28.96
28.95
15.0
18.97
18.98
18.99
19.01
19002
19.03
19.03
19004
19.04
19.04
19.04
20.0
14.04
14.05
14.06
14.07
14.08
16.08
14.09
14.09
14.09
14.09
14.09
25.0
II.I0
11.10
11.11
11.12
II.12
11.13
II.13
11.13
11.13
11.13
11.12
30.0
9.13
9.14
%14
9.15
9.15
9.16
9.16
9.16
9.16
9.16
9.16
35.0
7.74
7.74
7.74
7.75
7.75
7.75
7.76
7.76
7.76
7.76
7.75
40.0
6.6Y
6.69
6.70
6.70
6,70
6.71
6.71
6.71
6.71
6.71
6,70
45.0
5.88
5.88
5.89
5.89
5.89
5.89
5.89
5,89
5.89
5.89
5.89
50.0
5.23
5.24
5.24
3.24
5.24
5.24
5.25
5.25
5.25
5.24
3.24
55.0
4.71
4.71
4.71
4.71
6.72
4.72
6.72
4.72
4.72
4.72
4.71
60.0
4.27
4.27
4.2~
4.28
4.28
4.28
4.28
4.28
4.28
4.28
6.28
65.0
3.90
3.91
3.91
3.91
3.91
3.91
3.91
3.91
3.91
3.91
3.91
70.0
3.59
3,59
3.59
3.60
3.60
3,60
3.60
3.60
3.60
3.60
3.59
75.0
3.32
3.32
3.32
3.32
3.33
3.33
3,33
3,33
3.33
3.32
3.32
Thermodynamic data for heat pump systems operating on R 2 2
115
Table 6. Theoretical Rankine coefficients of performance (COPh for a range of lifts and condensing temperatures for R 2 2
55.0
(Tco~rv)oc~ 2t.8st
56.0
57o0
58.0
59.0
60.0
61.0
62.0
63.0
64.0
63.0
22.346
22.848
23.359
23.879
26.6o7
26.963
25.688
26.o63
26.6o6
27.178
1
10.0
28.93
28.93
28.94
28.91
28.86
28.84
28.86
28.82
28.75
28.71
28.65
15.0
19.04
19.02
19.02
19.00
18.98
18.98
18.96
18.95
18.91
18.88
18.84
20.0
14.09
16.08
14.08
14.06
14.05
14.06
14.03
14.02
13.99
13.97
13.94
25.0
11.12
11.12
11.]2
11.11
11.10
11.09
11.08
11.07
11.03
11.03
11.01
30.0
9.16
9.15
9.15
9.14
9.13
9.12
9.12
9.11
9.09
9.0e
9.06
35.0
7.75
7.75
7.75
7.76
7.73
7.73
7.72
7.71
7.70
7.69
7.67
40.0
6.70
6.70
6.70
6.69
6.69
6.68
6.68
6.67
6.66
6.65
6.63
63.o
5.u9
5.89
5.89
3.88
5.88
5.87
5.86
5.86
5.85
5.84
5.83
50.0
5.24
S.2t
5.26
5.23
5.23
3.23
5.22
5.21
5.21
5.20
5.19
33.0
6.71
4.71
6.71
4.71
4.70
4.70
6.69
4.69
4.68
4.67
4.67
60.0
6.28
4.27
4.27
4.27
6.27
6.26
6.26
4.25
4.25
&.24
4.23
65.0
3.91
3.91
3.90
3.90
3.90
3.89
3.89
3.89
3.88
3.87
3.87
70.0
3.59
3.59
3.59
3.39
3.58
3.58
3.58
3.57
3.57
3.56
3.56
73.0
3.32
3.32
3.32
3.32
3.31
3.31
3.31
3.30
3.30
3.29
3.29
Table 7 Theoretical Rankine coe~cients of performance (COPh for a range of lifts and condensing temperatures for R22 ,
!
65.0
66.0
67.0
68.0
69.0
70.0
71.0
27.178
27.758
28.349
28.968
29.558
30.177
30.803
72.0
73,0
31.440: 32.089
74.0
J 73.0 I
32.746 133.412
10.0
28.65
28.63
28.54
28.49
28.43
28.24
28.21
28.16
27.93
27.8~
27.81
IS.O
18.84
18.82
1~.77
18.72
18.66
18.58
18.35
18.51
18.39
18.33
18.27
20.0
13.94
13.92
13.89
13.86
13.73
13.69
13.61
13.55
13.51
25.0
11.01
10.99
10.97
10.94
1 3 . 8 1 1 13.75 i 10.91 10.87
10.84
10.81
10.75
10.71
10.67
30.0
9.06
9.05
9.02
9.00
8.98
8.94
8.92
8.90
8.85
8.81
8.78
35.0
7.67
7066
7064
7.62
7.60
7.57
7.55
7.33
7.50
7.47
7.44
40.0
6063
6.62
6.61
6.59
6.57
6.55
6.33
6.51
6.48
6.46 I
6.43
43.0
5.83
5.82
3.80
5.79
3.78
3.76
5.76
3.72
3.70 i
5.67
I
5.65
30.0
5.19
5.18
5.17
S. lS
5.14
5.12
5.11
S.09
5.07
5.05
35.0
6.67
4.66
6.65
6.64
6.62
6.61
4.60
4.58
&.56
4.54
4.53
60.0
4.23
6.22
6.22
6.21
6.19
4.18
6.17
6.16
4.14
4.12
6.11
65.0
3.87
3.86
3.85
3.84
3.83
3.82
3.81
3.~0
3.78
3.77
3.75
5.03
70.0
3.56
3.55
3o5&
3.53
3.52
3.51
3.50
3.69
3.48
3.47
3.45
75.0
3.29
3028
3.28
3.27
3.26
3.25
3.24
3.23
3.22
3.21
3.19
116
R ZYLLA et . I
Table 8 Theoretical Rankine coefficients of performance ICOPh for a range of lifts and condensing tempera tures for R22
75.0 ~co.TEv)oC ~ar)
76.0
II
77.0
78.0
79.0
80.0
81.0
83.0
38.370 139"122
84.0
83.0
34.090134.779i
35.476
10.0
27.81
27,51 i 27.34
27.10
27.00
26.94
26.24
25.59
18,27
18.12 I 17,99 I 17,87
17.77
17.68
17.36
26.07 i 17.40 i 17.16
25.91
15.0
17.05
16.92
20.0
13.51
13.42
13.24
13.18
13.09
12.90
12.88
12.73
12.63
12.52
25.0
10.67
10,60 i 10.54 ! 10,67
10.19 ! 10.07
30.0
8,7~
8.73
8.68
35.0
7.44
7.39 !
40.0
6.43
45.0
5.65
50.0
5.03
13.33
36.183 ....... 36.902!37.633
82.0
35.412
26.37!
39.883 4 0 . 6 5 5
10.41
10034
10.22
10.00
9.90
8.62
8.57
8.52
8.62
8.39 I:
8.3O
8.23
8.15
7.35
7.30
7.26
7.22
7.14
7.11 /
7,04
6.98
6.9t
6,40 :
6.36
6,32
6.28
6.24
6,18
6.15 i
6.09
6.04
5.99
5.62 :
5.59
5.56
5.53
5.49
5.44
5.41
5.36
5.32
5.27
5.00
4.98
4.95
4.92
4.89
4.85
4.82
4.78
4.74
4.69
t
:
I
55.0
4.53
4.50 ! 4.48
4.45
4.43
4.40
4.36
4.34
4.30
4.27
4.23
60.0
4,11
4.09
4,06
6.04
6.02
3.99
3.96
3.94
3.91
3,87
3.84
65.U
3.75
3.74
3,72
3.70
3.67
3.65
3.62
3.60
3.57
3.54
3.51
70.0
3.45
3.44
3.42
3.40
3.38
3.36
3.34
3.32
3.29
3.26
3.23
75.0
3,19
3.18
3.16
3.15
3.13
3.11
3,09
3.07
3,04
3.02
2.99
Table 9. Compression ratios Pco/PEvfor a range of liRs and condensing temperatures for R22
(TC~O.5,Ev)or~r )
--%
15.0
16.0
7,877
8.109
17.0
18.0
19.0
20.0
21.0
2200
23.0
2400
8.346
8.588
80835
g.087
9.346
9.60tI
9 . 8 7 8 J 10.152
25.0 10.632
i
10.0
1.353
1.350
1.347
1.344
1.341
10338
1.335
1.333
1.330
1.327
1.324
15.0
1.587
1.582
1.5761
1.571
10566
1.561
1.556
1.551
1.546
1,541
1.536
20.0
1.874
1.865
1.857
1.868
1.84~
1.831
1.823
1.815
1.807
1.799
1.792
25.0
2.229
2.215
2.201
2,188
2,175
2.162
2.150
2.138
2.126
2.114
2.102
30.0
2.669 I 2.669
2.629
2.609
2,590
20571
2.553
2.535
2.517
20500
20482
35.0
3,222
30163
3.135
3.107
30080
3,0$3
30027
3.001
2.976
2.952
3.193
60.0
3.923
3.880
3.838
3.797
3.757
3.718
3.680
3.662
3.606
3.570
30535
45.0
4.819
6.757
4.697
4.638
4.581
6.526
40472
60419
4.367
4.317
4.268
50.0
5.976
5.888
5.803
5.719
5.638
50559
5.483
5.408
5.335
5.26~,
5.195
55.0
7.490
7.364
70241
7.122
7.007
6.895
6.787
6.681
8.578
6.479
6.382
60.0
9.493
9.311
9.136
8.965
8.801
80641
8.487
8.338
8.192
8.052
7.915
65.0
12.177
11.915
11.661
110416
11.180
10.952
10.732
10.519
10.312
10.113
9.920
70.0"
15.825 1 5 . 4 6 3
15.074
14.719
16.378
14.049
13.732
13.427
13.131
12.847
12.573
75.0
20.858
19.754
19.234
18.737
18.257
17.798
17.356
16.930
16.522
16.128
200294
Thermodynamic data for heat pump systems operating on R22
117
Table 10 Compression ratios Pco/PEvfor a range of lifts and condensing temperatures for R22
25o0 10.432
26.0
27.0
10.718 !11.010
28.0
2900
30.0
31.0
32.0
3300
3400
35.0
11.307
11.611
11.920
12.236
12.558
12.886
13.220
13.561
10.0
1.324
1.322
1.319
1.317
1.314
1.312
1.309
1.307
1.305
1.302
1.300
15.0
1.536
1.531
1.527
1.522
1.518
1.513
1.509
1.505
1.501
1.496
1.492
20.0
1.792
1.784
1.777
1.769
1.762
1.755
1.748
1.761
1.735
1.728
1.722
25.0
2.102
2.091
2.080
2.037
2.027
2.016
2.007
1.997
2,482
2,466
2,449
2.069 I 2.058 I 2,433 2,418
2.047
30,0
2,402
2,387
2,372
2,357
2,343
2,329
35,0
2,952
2,928
2,904
2,881
2,t;59
2,837
2,815
2,79/*
2,773
2,753
2,733
40,0
3,535
3,501
3,468
3,436 I 3,404
3,373
3,342
3,313
3,283
3,255
3,227
45.0
4.268
4.220
4.173
I 4.128 ! 4.083
4.040
3.997
3.956
3.915
3.876
3.837
50.0
5.195
5.128
5.063
4.999
4.937
4.877
4.818
4.760
4.704
4.649
4.596
55.0
6.382
6.288
6,196
6.107
6.021
5.937
5,855
5.775
5,697
5,622
5.548
60,0.
7,915
7,783
7,655
7,530
7,410
7,292
7,178
7,068
6,960
6,855
6,754
65,0
9,920
9,734
9,553
9,378
9,209
9,045
8,886
8,731
8,582
8,437
8,296
70.0
12.573
12.3041
12.052
11.805
11.566 1 1 . 3 3 5
11.112
10.896
10.687
10.485
10.290
75.0
16.128
15.749
15.386
15.032
14.693
14.051
13.747
13.453
13.170
12.896
14.366
Table 11. Compression ratios Pco/P~v for a range of lifts and condensing temperatures for R22
t0.0
35.U
36.0
37.0
38.0
39.0
40.0
13.561
13.909
14.263
14.624
14.991
15.365
1.300
1.298
1.295
1.293
1.291
1.289
41.0
42.0
15.746!16,136 1.287
1.285
43.0
44.0
45.0
16,529
16.932
17.341
1.283
1.281
1.279
15.0
1.692
1.488
1.484
1.481
1.477
1.473
1.469
1.465
1.462
1.458
1.455
20.0
1.722
1.715
1.709
1.703
1.697
1.691
i.685
1.679
1.673
1.668
1.662
25.0
t.997
1.987
1.978
1.969
1.933
1.925
1.916
1.908
I 1.96U I 1.~51
1.942
30,0
2,329
2,315
2,302
2,28W
2,275
2,262
2,250
2,237
2,225
2,213
2,202
35,0
2,733
2,713
2,694
2,675
2,657
2,639
2,621
2,604
2,586
2,570
2,553
40.0
3.227
3.200
3.173
3.147
3.121
3.096
3.072
3.047
3.024
3.001
2.978
45.0
3.837
3.799
3.762
3.726
3.691
3.656
3.622
3.589
3.557
3.525
3.494
50.0
4.596
4.544
4.493
4.443
4.395
4.347
~.301
4.256
4.212
4.169
4.126
$$.0
5.548
5.476
50406
5.338
50272
5.207
5.144
5.082
5.022
4.964
4.906
60.0
6.754
6.455
6.559
6.466
6.374
6.286
6.200
6.116
6.034
5.954
5.877
65.0
8.296
8.160
8.027
7.899
7.773
7.652
7.534
7.419
7.308
7.200
7.094
70.0
10.290
10.100
9.917
9.739
9.567
9.400
9.237
9.080
8.928
8.780
8.636
75.0
1~.896
12.631
12.376
12.129
11.889
11.658
11.434
11.218
11.008
10,805
100608
H.X.S.! 2---C"
R. ZYLLA et al.
118
T a b l e 1 2 C o m p r e s s i o n r a t i o s Pco/PEv for a r a n g e o f liRs a n d c o n d e n s i n g t e m p e r a t u r e s for R22 ~ , ~ c o °C ~co(Pco
45.0
46.0
47.0
48.0
49.0
50.0
51.0
52.0
53.0
54.0
55.0
17.341
17.757
18.182
18.614
19.053
19.500
19.954
20.416
20.886
21.364
21.851
10.0
1.279
1.277
1.275
1.273
1,271
1.269
1.267
1,265
1.264
1.262
1.260
15.0
1.455
1.451
1.448 [ 1.444
1.441
1.438
1.435
1.431
1.428
1.425
1.422
20.0
1.662
1.657
1.6511
1.646
1.641
1.636
1.631
1.626
1.621
1.616
1.611
25.0
1.908
1.900
1.892 I 1.884
1.~77
1.869
1.862
1.854
1.847
1.840
1.833
30.0
2.202
2.190
2.1791
2.108
2.157
2.146
2,135
2.125
2,114
2.104
2.095
(Tco~Oc~ "
1
q
i 35.0
2.553
2.537
2.521 i
2.506
2.491
2.476
2.461
2.4461
2.432
2.418
2.405
40.0
2.978
2.956
2.934 i 2.913
2,892
2.871
2.851
2.831
2.812
2.793
2.774
45.0
3.494
3.464
3.434
3.377
3.349
3.322
3.295
3.268
3.243
3.217
3.405
50.0
4.126
4.085
4.045 i 4.006
3.967
3.929
3.893
3.856
3.821
3.786
3.753
55.0
4.906
4.851
4.796
4.743
4.691
4.640
4.591
4.542
4.495
4.448
4.403
60.0
5.877
5.801
5.727
5.656
5,585
5.517
5.451
5.386
5.322
5.260
5.200
65.~
7.094
6.992
6.892
6.795
6.700
6.608
6.519
6.431
6.346
6.263
6.182
I
70.0
8.636
8.496
8.361
8.230
8,102
7.977
7.857
7,739
7,624
7.513
7.405
75.0
10.608
10.417
10.233
10.054
9.880
9.711
9.548
9.389
9.234
9.085
8.939
T a b l e 13. C o m p r e s s i o n r a t i o s Pco/PEv for a r a n g e o f lifts a n d c o n d e n s i n g t e m p e r a t u r e s for R 2 2
'"°
"'°
'"°
"'°
,.o
,o.o
,,.o
,.o
i
,,.o
21,851
22.346
22.848
23.159
23.879
24.407
24.943
25°488
26.043
26.606
27,178
10.0
1.260
1.258
1.237
1.255
1.253
1.252
1.230
1.248
1.247
1.245
1.244
15.0
1.422 I
1.419
1.416
1.413
1.410
1.408
1.405
1.402
1.399
1.396
1.394
20.0
1.611
1.607
1.602
1.597
1.593
1.588
1.584
1.580
1.576
1.571
1.567
25.0
1.833
1.826
1.819
1.813
1.806
1.800
1.793
1.787
1.781
1.775
1.769
30.0
2.095
2.085
2.075
2.066
2.057
2.0/*8
2.038
2.Q30
2.021
2.012
2.004
35.0
2.405
2.391
2.378
2.365
2.352
2.340
2.327
2.313
2.303
2.291
2280
40.0
2.774
2.756
2.7)8
2.720
2.703
2.686
2.669
2.653
2.637
2.621
2.605
45.0
3.217
3.193
3.188
.3.145
3.121
.3.099
3.076
3.054
.3.033
3.011
2.991
50.0
3.753
3.720
3.687
3.655
3.624
.3.594
3.564
3.535
3.506
3.478
3.450
55.0
4.403
4.359
4.316
4.273
4.232
4.192
4.152
4.113
4.075
4.038
4.002
60.0
5.200
5.141
5.083
5.027
4.972
4,918
4.866
4.814
4.764
4.715
4.667
65.0
6.182
6.104
6.027
5.952
5.879
5.808
5.7)8
5.670
5.604
5.540
5,477
70.0
7.405
7.300
7.197
7.097
7.000
6.906
6.813
6.723
6.636
6.551
6.467
75.0
8.939
8.798
8.661
8.527
8.398
8.271
8.148
8.029
7.913
7.800
7.690
Thermodynamic data for heat pump systems operating on R22 i
Table 14 Compression ratios
! 19
!
Pco/PEv for a range of lifts and condensing temperatures for R22
65.0
66.0
67.0
68.0
69.0
70.0
71.0
72.0
73.0
74.0
73,0
27.178
27.758
28.349
28.948
29.558
30.177
30.803
31.460
32.089
32.746
33.412
10.0
1.244
1.242
1.241
1.239
1.238
1.236
1.235
1.234
1.232
1.231
1.229
15.0
1.394
1.391
1.389
1.386
1.384
1.381
1.378
1.376
1.374
1.371
1.369
20.U
1.567
1.563
1.559
1.555
1.551
1.548
1.544
1.540
1.336
1.533
1.529
25.0
1.769
1.763
1.757
1.751
1.746
1.740
h735
1.729
1.724
1.719
1.713
30.0
2.0(~
1.996
1.988
1.980
1.972
1.964
1.936
1.949
1.941
1.934
1.927
35.0
2.280
2.269
2.257
2.246
2.236
2.225
2.215
2.204
2.194
2.184
2.175
40.0
2.605
2.590
2.575
2,560
2.546
2.532
2.517
2,506
2.490
2,47P
2.664
45.0
2.991
2.970
2.950
2.931
2.911
2.893
2.874
2.856
2.838
2.820
2.803
50.0
3.450
3,423
3.397
3.371
3.346
3.321
3.296
3.272
3.269
3.225
3.203
55,0
4.002
3.966
3.931
3.897
3.864
3.831
3.799
3.767
3,737
3.706
3.677
60.0
4.667
4.621
4.575
4.530
4.486
4.443
4.401
4,360
4.320
4.280
4.242
65.0
5,477
5.415
5.355
5.296
5.238
5,183
5,127
$,074
5,021
4.970
4.920
70.0
6.467
6.386
6.307
6.230
6.154
6.081
6.009
5.939
5.870
5.803
5.738
7 5.0
7,690
7.582
7,478
7,376
7.277
7.181
7.086
6.994
6.906
6.818
6.733
Table 15 Compression ratios
Pco/P~v for a range of liRs and condensing temperatures for R22
., o0
-<
(TCO-TI[V)
75.0
76.0
77.0
7B.0
79.0
80.0
81.0
82.0
83.0
84,0
85.0
33.412
34.090
34.779
35.476
36.183
36.902
37.633
38.370
39.122
39.883
40.655
10.0
1.229
1.228
1.227
1.226
1.224
1.223
1.222
1.220
1.219
1.218
1.217
15.0
1.369
1.367
1.365
1.362
1.360
1.358
1.356
1.353
1.351
1.349
1.347
20.0
1,529
1.526
1.522
1.519
1.515
1.512
1.509
1.505
1.502
1.499
1.496
25.0
1.713
1.708
1.703 : 1.699 i
1.694
1.689
1.684
1.679
1.675
1.670
1.666
30.0
1.927
1.920
1.913!
1.906
1.899
1.892
1.886
1.879
1.873
1.867
1.861
2.146
2.137
2.128
2.119
2.110
2.102
2.093
2.085
I
I
35.0
2.175
2.165
2.156
40.0 45.0
2.464
2.451
2.438 i 2.426
2.414
2.402
2.390
2.378
2.367
2.356
2.344
2.803
2.786
2.770 , 2.753
2.737
2.721
2.706
2.690
2.675
2.661
2.646
50,0
3.203
3.1~1
3,159 : 3.137
3,116
3.096
3.076
3.055
3.036
3.017
2.998
t
55.0
3,677
3.648
3.619
3.592
3,564
3.537
3.511
3.485
3,460
3.435
3.411
60.0
• 4.242
4.204
4.167
4.131
4.095
4.061
4.027
3.993
3.961
3.928
3.897
65.0
4.920
4.871
4.823
4.776
4.730
4.685
4.641
4.$98
4.556
4.514
4.474
70.0
5.738
5.674
5.612
5.551
5.492
5.434
5.377
5.321
5.267
5.213
5.161
75.0
6.733
6.650
6.569
6.490
6.413
6.337
6.266
6.192
6.122
6.053
5.986
120
R. ZYLLA e t U/.
Since the compression from point $2 to point D1 is isentropic, ~s2 = (~)Ol where ~ is the entropy per unit mass. For design purposes, the enthalpy per unit mass of the superheated vapour at D1 can be approximately related to the enthalpy per unit mass of the saturated vapour at point D2 by the equation HD, = HD2 + (¢)s2 - @D2)Tco.
(2)
Equations (1) and (2) can be used to calculate (COPh values for any desired condensing temperature Tea and temperature lift (Tea - TEv) from the saturated properties of the chosen working fluid. Here, the theoretical Rankine coefficient of performance (COPh and the compression ratio Pco/PEv have been calculated for R22 for temperature lifts of 10-75°C in 5°C increments and condensing temperatures Tea for every degree in the range of 15-85°C. The basic thermodynamic properties of R22 used in the calculations have been taken from 'Thermodynamic Properties of Arcton 22 SI units' published by Imperial Chemical Industries Limited, Imperial Chemical House, Millbank, London SWlP 3JF. Tables 2-8 list the calculated (COPh values and Tables 9-15 the calculated Pea/PEr values. Figures 2-7 are plotted from the data listed in the tables. DISCUSSION OF DERIVED DATA
In Fig. 3, the compression ratio Pco/PEv and theoretical Rankine coefficient of performance (COPh are plotted against the temperature lift (Tco - TEv) for a condensing
20
5. TC 0 =6 0 " C
--19
18 = 4
. 7 bar
.~E o -- 15 _
-
e==
,=_o
.
~
-t4
..~ a.
-,3
8
--t2
a.w
o 3.0 0..o
-- ~0
.8_
- 8
oE
-6
,-, o
._e
2.0 --
==
-- 5
--2
I
.
C
20 ~
30 (
~4 0
) 50
O
60
I,-
0
Temperature lift (Tea- TEv), °C
t
0
1
10
I
20
I
30
1
40
I
50
Temperature lift (TD - T s ) , =C wilt) 20=C drop in heat exchangers
Fig. 3. Compression ratio and theoretical Rankine coefficient of performance against temperature lift for R22 at a condensing temperature of 60°C and a condensing pressure of 24.407 bar.
Thermodynamic data for heat pump systems operating on R22 20
121 2O
19 18
Condensing m ~ u r e
17
T~.,5-c
,6
15 Tco'85"C
_
~.
15 'i 1 4 . "o -
.E
,3 -~ O.
.!
°
~
%.,5.c
,~ ~
-
II
i
lO ,~
I0
9 "6
,I 0
to
2o
3o
4o
50
60
7o
Temperature lift (Tco-TEv) , "C Fig. 4. Variation of compression ratio and theoretical Rankine coefficient of performance with temperature lift and condensing temperature for R22.
(TCO-TEV)"20°C
13 l_ 12
/(Tco- TEO, 25"(:
II
I09
"/" ~ c
o"'rEv )" 3o-c
8
15"C
7
~L. . . . .
--~-
TEV)" 40"C
5-4 3
Condensing tempsrolure
2-
T:o. es'c
'-
c
I
2
I
3
I
4
l
5
I
6
I
7
Compression rotio Pco/PEv, dims~oNess
Fig. 5. Th~retical Rankine e~fl~eient of perfonmance against compression ratio showing the influence of temperature lift and condensing temperature for R22.
122
R. ZYLLA el (//.
~5 Temperature lift ( T 0- T v) =2OoC
13-
~
12
-
E ~5
(TCO- TEv) " 25=C
(T=-
._~
7 -
(Tr_x)-TEJ- 40"C
5
(Tco-TEv)= 4---
315
Z~
30 4~ 5~ 6~ Condensing temperature Tco, °C
7k
Fig. 6. Theoretical Rankine coefficient of performance against condensing temperature for various temperature lifts for R22.
temperature 60°C. The effective temperature lift will be reduced by 20°C for a temperature drop of 10°C in each of the heat exchangers. Figure 4 shows that Pco/PEv values for a given temperature lift ( T c o - TEv) are extremely sensitive to the condensing temperature Tco. In contrast, the (COP)R values are almost independent of the condensing temperature. Figure 4 highlights the necessity for heat pump systems to be carefully matched in a specific application. This is further illustrated by Fig. 5, which is a plot of (COP~ against Pco/PEv for various temperature lifts ( T c o - TEv). Figure 5 implies that relatively high coefficients of performance are only possible for relatively low t©mperature lifts and compression ratios. The heating of buildings and the operation of fractional distillation columns are amongst the potential applications for such systems. The sensitivities of (COPk and Pco/P~v to the condensing temperature Tco at various temperature lifts (T¢o - TEv) are illustrated in Figs 6 and 7 respectively. Figure 6 shows that the theoretical Rankine coefficient of performance (COP)= increases almost linearly with the condensing temperature for all temperature lifts and then decreases after reaching maxima in the region of T¢o = 50°C. The maximum is more pronounced for lower temperature lifts. Figure 7 shows the variation of compression ratio with condensing temperature for various temperature lifts.
Thermodynamic data for heat pump systems operating on R22
123
t 17
16 15 .-
Temperature Iif!
•6
i2--
:> 0,,.w
If --
0-8 o
I0--
~
9
._~
U
15
25
:55
I
45
I
55
I
65
I
75
i
85
Condensing temperolure Tco, "C
Fig. 7. Compression ratio against condensing temperature for various temperature lifts for R22.
NOMENCLATURE
(COP)x Hx /'co PEV Tco TD TEV Ts W 0x
Rankine coefficient of performance of a heat pump system [dimensionless] Enthalpy per unit mass at state condition X [kJ kg - t ] Pressure in the condenser of a heat pump system [bar] Pressure in the evaporator of a heat pump system [bar] Temperature of the working fluid in the condenser ['K or °C] Temperature of the heat sink fluid from the heat pump system [K or °C] Temperature of the working fluid in the evaporator [K or °C] Temperature of the heat source fluid to the heat pump system [-K or °C] Work rate to the compressor of a heat pump system [kW] Entropy per unit mass at state condition X [-kJ kg- ~ K - 1]